can black coffee raise blood sugar?

Coffee for Diabetics, Good or Bad? Raises Blood Sugar or NOT? SugarMD.

According to specialists, those who drink coffee have a much lower risk of type 2 diabetes than those who don't drink coffee. However, if you are already diabetic, then be careful with foods containing caffeine - it increases blood sugar levels and reduces the effect of insulin, which prevents you from maintaining a constant blood sugar level.

Caffeine is believed to influence the processing of sugar in the body and to contribute to adrenaline production. This hormone increases blood sugar levels. If you have type 2 diabetes and don't understand why it is difficult to keep your blood sugar level constant, it may be time to reduce your coffee consumption.

There is a clear difference in how people with diabetes and people without diabetes react to caffeine. In a study conducted in 2008, typical coffee lovers with type 2 diabetes kept their blood sugar levels constant and engaged in daily activities.

During the day, it was shown that immediately after they had coffee, their blood sugar levels went up. On those days when they drank coffee, their blood sugar levels were higher than on those days when they didn't.

That depends, is it only black coffee? Is anything added to it? If the answer is no, then you will find purely black coffee will actually lower your blood sugar due to the water content and the lack of carbohydrates from the coffee beans. However the blood sugar will continuously rise if it is not provided with the insulin that the pancreas creates, so if we assume that the person drinking the black coffee is diabetic or has some form of pancreatic dilemma, then we could also assume that coffee will lower the blood sugar. If you are simply curious about whether it will change the glucose in the bloodstream for someone without any health issues, the answer is, yes but not by much…see the blood sugar of the average human ranges from 60–180 mg/dl, going over or under these numbers might mean you have some underlying problem going on, it also might mean nothing, I don’t know your lifestyle. Let’s say your blood sugar is currently at 82 mg/dl, you randomly decide to drink some black coffee straight, your blood sugar will in about 10–20 minutes drop to 80–81 assuming you have had the same blood sugar that entire day, with no previous exercise that might alter the results.

Black Coffee Blood Sugar Response

Last month, I started an experiment to better understand how different foods and lifestyle decisions impact blood sugar, using a constant-glucose-monitoring device.

For the last few weeks, I’ve been testing whether or not drinking coffee raises my blood-sugar levels.

The answer may seem obvious as coffee contains no sugar, but some people believe coffee can have an effect, and our first coffee experiment indicated just that.

Since then, I’ve repeated the experiment twice. Here’s what I found.

Planning the coffee experiment

I designed the following experiment: I would drink a cup of coffee and measure my blood-sugar levels two hours prior to and after drinking it. Then I would analyze the data to see if drinking coffee seemed to raise my blood-sugar levels.

To increase the reliability of the experiment, I made sure of four things:

1. I would drink the coffee black – nothing would be added to it.
2. I wouldn’t eat or drink anything else, feel stressed, nor do any form of exercise, 2 hours prior to and after drinking the coffee.
3. I would eat ketogenic.
4. I would go to bed and wake up around the same time as I normally do.

It was coffee time.

Drinking coffee

The house was quiet, but I was up, feeling excited about doing another experiment. Everything was ready – beans, scale, grinder, and coffeemaker. The glucose sensor was safely installed in my body – constantly monitoring any change in blood-sugar levels.

Using the above food scale, I put 0.63 ounces (18 grams) of coffee beans into the grinder (about the same amount as for a double espresso). I turned it on. “Grrrrooooooooooooooooouhhh”, it sounded like an elephant had been let loose in the kitchen!

After 20 seconds, the noise finally stopped. I picked up the coffee-bean container, held it to my nose, and inhaled. “Mmmmmmmm, what a delicious smell!”.

I poured the coffee into the Bialetti coffee maker along with 7 oz (2 dl) of boiling water. A few minutes later the coffee was ready. I immediately took a sip. “Oooh, powerful!”.

The coffee didn’t taste as well as it normally does as I hadn’t added any cream – my favorite coffee is the Creamuccino – coffee with steamed cream – but I couldn’t have that this morning as it would affect the experiment. Still, the coffee was nice and a few minutes later there was no more.

Using the constant-glucose-monitoring app I was watching any change in my blood-sugar levels like a hawk. “Ohhhhhh, interesting!”.

Coffee does NOT seem to raise my blood-sugar levels

The graphs below show my blood-glucose levels over a 4-hour period for three separate experiments. The blue line is the blood glucose on a morning I drank coffee. The red line is on a morning without coffee.

Experiment one

The first experiment indicated that coffee may raise my blood sugar. But only slightly:

The graph above could suggest that drinking coffee prevents my blood-sugar levels from dropping to the same levels as the morning when I didn’t drink coffee.

Experiment two

The second experiment indicates that coffee does NOT noticeably raise my blood sugar. There’s a lot of variety in my blood-glucose levels on these two days, but to us it seems that coffee does not raise my blood sugar relative to not drinking coffee (the control).

Experiment three

The third experiment also suggests that coffee does not raise my blood sugar much. My blood-sugar levels are quite flat, both on the morning when I drank coffee and the morning I didn’t, indicating that the coffee didn’t impact my blood-sugar levels much.

Conclusion

The chart below shows my average blood-sugar levels based on the three experiments.

To me, this indicates that drinking coffee does not significantly raise my blood-sugar levels.

But, the chart also indicates that my blood-sugar levels on coffee-drinking mornings are on average slightly higher than on mornings I didn’t drink coffee.

However, this difference is not significant and could be due to random variance in blood-sugar levels (see for example how the blood-sugar levels start out higher on coffee-drinking mornings even though I haven’t had any coffee yet).

No significant change in blood-ketone levels

The below chart shows my average blood-ketone levels on coffee-drinking mornings for experiment two and three (regretfully, I didn’t measure ketones for the first experiment).

To us, this graph also seems to indicate that coffee does not raise my blood sugar significantly.

If coffee had raised my blood-sugar levels significantly, we would have expected insulin levels to increase as well, causing a subsequent drop in ketone levels. But there was no significant decrease in ketone levels after drinking coffee.

What happens to your blood-sugar levels when you drink coffee?

Please note: This is a n=1 self experiment and my findings may not apply to you. I am a 36-year old insulin-sensitive male, weigh 152 pounds (69 kg), exercise for 10-15 minutes five times a week, with no history of obesity or diabetes.

Although coffee doesn’t seem to raise my blood-sugar levels, the same may not be the case for you.

What happens to your blood sugar when you drink coffee? Let us know in the comments below.

How to test

To test what happens to your blood-sugar levels after drinking coffee, do this:

1. Eat and drink nothing for 2 hours.
2. Measure your blood glucose – this is your baseline.
3. Drink a cup of coffee with nothing added to it (no sugar, no sweeteners, no milk, no cream etc.). Don’t eat or drink anything else for the next two hours, and avoid exercise and stress (these can impact blood sugar).
4. Measure your blood-sugar levels every 30 minutes up to two hours after drinking the coffee (five times in total including the baseline measurement).
5. Evaluate your results. Is there a significant increase or reduction in your blood-sugar levels? *

* It’s normal for blood-sugar levels to fluctuate during the day even when you don’t eat. Therefore, smaller changes – up or down 0.5 mmol/L (10 mg/dl) for example – could be random variation and not caused by drinking coffee.

What do you want us to test next?

We’ve received lots of suggestions for what else to test, for example sugar alcohols, more artificial sweeteners, fasting, alcohol, and resistant starch. What else would you like us to test?

Thanks for suggesting ways to improve these experiments. As per your request, we’ll measure ketones in addition to blood sugar. However, for the experiments we’ve already done but not yet published, ketones data may lack.

Measuring insulin levels is tricker. Do you know of a reliable and simple way to measure it several times per hour? Let us know in the comments below.

Coffee and diabetes

Coffee was once condemned as being bad for your health. Yet, there’s growing evidence that it may protect against certain kinds of cancers, liver disease, and even depression.

Coffee causes Insulin Resistance (Don't Panic)

There’s also compelling research to suggest that increasing your coffee intake may actually lower your risk for developing type 2 diabetes. This is good news for those of us who can’t face the day until we get in our cup of java.

However, for those who already have type 2 diabetes, coffee could have adverse effects.

Whether you’re trying to lower your risk, you already have diabetes, or you just can’t go without your cup of joe, learn about coffee’s effects on diabetes.

What is diabetes?

Diabetes is a disease that affects how your body processes blood glucose. Blood glucose, also known as blood sugar, is important because it’s what fuels your brain and gives energy to your muscles and tissues.

If you have diabetes, that means that you have too much glucose circulating in your blood. This happens when your body becomes insulin resistant and is no longer able to efficiently uptake glucose into the cells for energy.

Excess glucose in the blood can cause serious health concerns. There are a number of different factors that can cause diabetes.

Chronic diabetes types are type 1 and type 2. Other types include gestational diabetes, which occurs during pregnancy but tends to go away after birth.

Prediabetes, sometimes called borderline diabetes, means your blood glucose levels are higher than usual but not so high you would be diagnosed with diabetes.

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Some signs and symptoms of diabetes include:

increased thirst

unexplained weight loss

fatigue

irritability

If you think you might have some of these symptoms, it’s important to talk to your doctor.

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Coffee and the possible prevention of diabetes

The health benefits of coffee for diabetes differs from case to case.

Researchers at Harvard tracked over 100,000 people for about 20 years. They concentrated on a four-year period, and their conclusions were later published in this 2014 study.

They found that people who increased their coffee intake by over one cup per day had an 11 percent lower risk of developing type 2 diabetes.

However, people who reduced their coffee intake by one cup per day increased their risk of developing diabetes by 17 percent. There was no difference in those drinking tea.

It’s not clear why coffee has such an impact on the development of diabetes.

Thinking caffeine? It may not be responsible for those good benefits. In fact, caffeine has been shown in the short term to increase both glucose and insulin levels.

In one small study involving men, decaffeinated coffee even showed an acute rise in blood sugar. Right now there are limited studies and more research needs to be done on the effects of caffeine and diabetes.

WERBUNG

Coffee And Diabetes | Will Caffeine Shoot my Blood Sugar Levels?

Coffee’s effect on glucose and insulin

While coffee could be beneficial for protecting people against diabetes, some studies have shown that your plain black coffee may pose dangers to people who already have type 2 diabetes.

Caffeine, blood glucose, and insulin (pre- and post-meal)

One 2004 study showed that taking a caffeine capsule before eating resulted in higher post-meal blood glucose in people with type 2 diabetes. It also showed an increase in insulin resistance.

According to a recent 2018 studyTrusted Source, there may be a genetic proponent involved. Genes may play a role in caffeine metabolism and how it affects blood sugar. In this study, people who metabolized caffeine slower showed higher blood sugar levels than those who genetically metabolized caffeine quicker.

Of course, there’s a lot more in coffee other than caffeine. These other things may be what’s responsible for the protective effect seen in the 2014 study.

Drinking caffeinated coffee over a long period of time may also change its effect on glucose and insulin sensitivity. Tolerance from long-term consumption may be what causes the protective effect.

A more recent studyTrusted Source from 2018 showed that long-term effects of coffee and caffeine may be linked to lowering risk of prediabetes and diabetes.

Fasting blood glucose and insulin

Another study in 2004 looked at a “mid-range” effect on people without diabetes who had been either drinking 1 liter of regular paper-filtered coffee a day, or who had abstained.

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At the end of the four-week study, those who consumed more coffee had higher amounts of insulin in their blood. This was the case even when fasting.

If you have type 2 diabetes, your body is unable to use insulin effectively to manage blood sugar. The “tolerance” effect seen in long-term coffee consumption takes a lot longer than four weeks to develop.

Habitual coffee drinking

There’s a clear difference in how people with diabetes and people without diabetes respond to coffee and caffeine. A 2008 study had habitual coffee drinkers with type 2 diabetes continuously monitor their blood sugar while doing daily activities.

During the day, it was shown that right after they drank coffee, their blood sugar would soar. Blood sugar was higher on days that they drank coffee than it was on days they didn’t.

Other health benefits of coffee

There are other health benefits of drinking coffee that aren’t related to diabetes prevention.

Newer studies with controlled risk factors have been showing coffee’s other benefits. They include potential protection against:

Parkinson’s disease

liver disease, including liver cancer

gout

Alzheimer’s disease

gallstones

These newer studies have also shown that coffee seems to decrease depression risk and increase ability to focus and think clearly.

Black Coffee and Diabetes

Coffee with added ingredients

If you don’t have diabetes but are concerned about developing it, be careful before increasing your coffee intake. There may be a positive effect from coffee in its pure form. However, the benefits aren’t the same for coffee drinks with added sweeteners or dairy products.

Daily diabetes tip

Coffee may be more popular than ever, but drinking it on a regular basis isn’t the best way to manage diabetes — even if (believe it or not) there’s growing evidence that it could help prevent diabetes.

Creamy, sugary drinks found at cafe chains are often loaded with unhealthy carbs. They’re also very high in calories.

The impact of the sugar and fat in a lot of coffee and espresso drinks can outweigh the good from any protective effects of the coffee.

The same can be said about sugar-sweetened and even artificially sweetened coffee and other beverages. Once sweetener is added, it increases your risk of developing type 2 diabetes. Consuming too many added sugars is directly linked to diabetes and obesity.

Having coffee drinks that are high in saturated fat or sugar on a regular basis can add to insulin resistance. It can eventually contribute to type 2 diabetes.

Most big coffee chains offer drink options with fewer carbs and fat. “Skinny” coffee drinks allow you the morning wake-up or afternoon pick-me-up without the sugar rush.

Some healthy tips to flavor your coffee include:

add vanilla and cinnamon as a healthy, zero carb option

choose an unsweetened vanilla milk option, such as coconut, flax, or almond milk

ask for half the amount of flavored syrup when ordering from coffee shops, or nixing syrup altogether

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Does coffee raise blood sugar?

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Risks and warnings

Even for healthy individuals, the caffeine in coffee can have some side effects.

Caffeine’s common side effects include:

headaches

restlessness

anxiety

As with most everything, moderation is the key in coffee consumption. However, even with moderate consumption, coffee does have risks that you should discuss with your doctor.

These risks include:

an increase in cholesterol with unfiltered or espresso-type coffees

an increased risk of heartburn

elevated blood glucose levels after a meal

Other things to keep in mind:

Adolescents should have less than 100 milligrams (mg) of caffeine each day. This includes all caffeinated drinks, not just coffee.

Young children should avoid caffeinated drinks.

Adding too much sweetener or cream can increase your risk of diabetes and becoming overweight.

Takeaway

No food or supplement offers total protection against type 2 diabetes. If you have prediabetes or are at risk for getting diabetes, losing weight, exercising, and consuming a balanced, nutrient-dense diet is the best way to reduce your risk.

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Taking up drinking coffee in order to stave off diabetes won’t guarantee you a good result. But if you already drink coffee, it may not hurt.

Try reducing the amount of sugar or fat you drink with your coffee. Also talk with your doctor about diet options, exercise, and the effects that drinking coffee might have.

Foods and drinks directly affect blood glucose levels. This means that dietary choices are especially important for people with diabetes.

Many people start the day with a cup of coffee, and various studiesTrusted Source have reported that drinking coffee could reduce the risk of developing type 2 diabetes.

This has led some people with diabetes to wonder whether coffee or possibly caffeine may be beneficial.

Coffee contains many chemicals beyond caffeine, and according to current research, it seems that some have beneficial effects, while others have less positive ones.

This article looks at scientific investigations into the effects of coffee on diabetes and diabetes risk.

Is coffee good for your health?

Image credit: Cavan Images/Getty Images

Coffee contains many chemicals that have different effects on the body, including caffeine and polyphenols.

Polyphenols are molecules with antioxidant properties believed to help prevent a wide range of diseases, including type 2 diabetes, heart disease, and cancers.

Antioxidants help keep the heart healthy. People with diabetes have a higher risk of developing heart disease and stroke, and eating plenty of foods that contain antioxidants may help reduce this risk. Read about antioxidant-rich foods here.

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Coffee also contains the minerals magnesium and chromium. Increasing magnesium intake has been linked to lower rates of type 2 diabetes.

However, coffee contains very small amounts of these nutrients, compared with other foods; it is far from the most reliable source of these minerals.

The following sections look specifically at how components of coffee may affect diabetes.

Coffee and type 2 diabetes risk

According to research, drinking 3 to 4 cupsTrusted Source of coffee per day could help reduce a person’s risk of developing type 2 diabetes.

In a large 2013 study, people who increased the amount of coffee that they drank by more than 1 cup per day over a 4-year period had an 11% lower risk of developing type 2 diabetes than those who made no changes to their coffee intake.

The study also found that people who decreased their coffee consumption by more than 1 cup per day had a 17% higher chance of developing type 2 diabetes.

In a press release, the lead author of the study, Shilpa Bhupathiraju, Ph.D., stated:

“Our findings confirm those of previous studies that showed that higher coffee consumption was associated with lower type 2 diabetes risk. […] Most importantly, they provide new evidence that changes in coffee consumption habit can affect type 2 diabetes risk in a relatively short period of time.”

In a reviewTrusted Source published a year later, scientists analyzed 28 studies, including more than 1 million total participants. The researchers found that both caffeinated and decaffeinated coffee reduced the risk of developing type 2 diabetes.

The accumulated evidence strongly suggests that drinking coffee may help protect against this condition.

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Does coffee affect blood glucose and insulin?

Plain coffee does not seem to directly increase levels of blood sugar, or blood glucose. This is good news for people with diabetes who like black coffee.

However, some research suggests that the caffeine in coffee could impair insulin sensitivity, which is not ideal for people with diabetes.

That said, other compounds in coffee — notably magnesium, chromium, and polyphenols — may play a role in improving insulin sensitivity, which may offset the effects of caffeine.

Because of this, some experts suggest that people with diabetes drink decaffeinated coffee — to get the benefits of components such as antioxidants and minerals without affecting insulin sensitivity.

Exercise

According to a small pilot studyTrusted Source in people with type 2 diabetes, drinking caffeine before exercising may reduce blood sugar levels.

Another studyTrusted Source in people with type 1 diabetes suggests that taking a caffeine supplement could modestly attenuate low blood sugar during exercise. However, the researchers caution that this could increase this risk of late-onset low blood sugar.

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Is caffeine harmful?

Caffeine is the major stimulant in coffee. It occurs naturally in coffee beans and green tea. Caffeine speeds up the central nervous system and may increase mental alertness, relieve tiredness, and improve concentration.

In the general population, the Food and Drug Administration (FDA)Trusted Source report, 400 milligrams of caffeine — or 4 to 5 cups of coffee — per day usually have no negative effects.

However, because research in people with diabetes has been mixed, it is a good idea to ask a healthcare provider about how much coffee is safe.

Some people are more sensitive to the effects of caffeine than others. This is true for people with or without diabetes.

Some experts suggest that decaffeinated coffee is the safest option for people with diabetes because it provides the benefits of other coffee components without the potential risks of caffeine.

It is also important to note that adding sugar or creamer to coffee increases blood sugar levels.

People with diabetes benefit from choosing drinks without added sugar.

Some people use artificial sweeteners, but researchTrusted Source indicates that some of these products, particularly sucralose, may affect blood sugar levels in a way that is harmful.

A diabetes-friendly noncaloric sweetener such as monk fruit may be a more healthfulTrusted Source choice when a drink needs sweetening. A person might try using a bit less each day, aiming to eventually cut out sweeteners altogether.

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Summary

Coffee contains many chemicals that have different effects on the body. Some are beneficial for people with diabetes, while others may be less healthful.

Research suggests that coffee may reduce a person’s risk of developing type 2 diabetes.

For people who live with diabetes, the guidance from scientists is mixed. Some studies say that caffeine may reduce insulin sensitivity, though other healthful chemicals in coffee could attenuate these effects.

For this reason, some doctors believe that switching to decaffeinated coffee is a safer bet.

It is crucial to note that coffee with sugar or creamer can raise blood sugar levels. For a person with diabetes, the most healthful way to drink coffee is black or with a natural alternative sweetener.

Black coffee can affect your blood sugar, causing it to rise. For some people, mainly diabetics, this can be a real problem. Controlling your blood sugar may mean you have to cut down on coffee intake. But although this effect is seen in people with diabetes, there is evidence that suggests drinking coffee can help reduce the risk of developing type 2 diabetes.

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Effect in Diabetics

A study published in "Diabetes Care" in 2007 looked at the effects of black coffee on blood glucose levels. Ten individuals with well-controlled type 2 diabetes, who habitually drank coffee, received either a 500 mg capsule of caffeine or a placebo. Those taking the caffeine had higher overall glucose levels and higher postprandial glucose levels than the control participants. The researchers say the mechanism behind caffeine and glucose levels may involve the hormonal regulation of uptake. They suggest that the presence of caffeine increases the hormone epinephrine, which reduces glucose metabolism. Another speculation concerns control of the brain's regulation of glucose uptake -- caffeine affects certain receptors inside the brain that might inhibit glucose clearance into the cells.

Effect in Non-Diabetics

Caffeine intake may actually help prevent the development of type 2 diabetes, explains Science Daily. People without diabetes are able to make up for the rise in glucose through the production of extra insulin. Insulin is the hormone that drives glucose clearance, and the body just needs to pump a little more out to take care of the effects of caffeine on blood glucose.

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Amounts

A habitual coffee drinker may be wondering how much caffeine will cause an effect. About 250 mg of daily caffeine can cause blood glucose disruption. This is the equivalent of 2 to 2.5 cups of black coffee per day. If you need to reduce the impact black coffee has on your blood glucose, cut down on your daily intake.

Possible Preventive Effect

If you do not have diabetes, black coffee may be helpful in preventing this chronic condition, according to a 2011 study from UCLA. Researchers identified a link between coffee consumption and the amount of sex hormone-binding globulin, SHBG, in the blood. People with low amounts of SHBG in the bloodstream are more likely to develop type 2 diabetes. Drinking caffeinated coffee influences the levels of SHBG in the blood. Researchers studied 359 newly diagnosed diabetics and 359 non-diabetic subjects to analyze coffee drinking habits and levels of SHBG. The subjects who drank at least four cups of coffee per day had higher levels of SHBG and were 56 percent less likely to be diagnosed with diabetes.

Caffeine appears to impair glucose metabolism and insulin response in the short term.

But long-term coffee consumption has been found in many studies to lower the risk of developing Type 2 diabetes.

Coffee contains other compounds—such as chlorogenic acids, also commonly found in fruits and vegetables—that may improve glucose metabolism in the long term.

THE TAKEAWAY: Don’t add coffee to your routine just for the health benefits—you can get the same healthy compounds through balanced eating—but unless you have impaired glucose metabolism, you probably don’t need to cut out your morning cup. If you want to avoid caffeine, decaf (and green tea) seem to convey similar long-term benefits.

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It’s easy to get confused about whether coffee is good or bad for you. First, it’s helpful to acknowledge that discussions about coffee are often discussions about caffeine since only about 10% of U.S. coffee drinkers choose decaf. And while we know caffeine is a stimulant, individual responses to its stimulatory impact and subsequent side effects vary considerably, due in part to our genetics. We can often feel caffeine’s effects within 15 minutes, but it can remain in our body for up to 10 hours. The liver mostly breaks it down, but it can interact with multiple systems, including the brain, the cardiovascular system, the respiratory system, and the kidneys. Even its impact on athletic performance varies among individuals. 

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But if we zoom out to look at coffee and not just caffeine, it perfectly illustrates the difference between short-term and long-term effects. Decades-long epidemiological studies find pretty consistently that drinking coffee lowers the risk of developing Type 2 diabetes. On the other hand, you may read headlines saying that a cup of coffee raises your blood glucose level. You might have experienced this first hand. And most studies of caffeine’s short-term effects show that it reduces insulin sensitivity. Coffee’s long-term benefits seem to stem from other compounds in the brew and are ultimately more potent than the immediate effects of its caffeine component. 

Here’s a look at the two sides of coffee. 

The Short Term: Caffeine Reduces Insulin Sensitivity

Since coffee on its own (no sugar, no dairy) doesn’t contain carbohydrates, simply drinking a cup shouldn’t raise glucose levels. To test its effect on glucose metabolism, researchers typically ask study participants to consume either caffeine or coffee with a meal or an oral glucose tolerance test (in which people drink a high-glucose beverage) and then monitor their insulin and glucose levels. What they’ve found is that insulin and glucose levels tend to rise. That suggests that caffeine causes a decrease in insulin sensitivity since the elevated insulin isn’t bringing down the glucose increase from the ingested carbs. In other words, caffeine seems to impair insulin’s effectiveness. Research has shown that insulin sensitivity drops in response to a single dose of caffeine following 72 hours of caffeine avoidance. It also drops after high coffee consumption over four weeks, suggesting the body does not build a tolerance to caffeine’s effect on insulin over time. 

Research shows the same effects in people with Type 2 diabetes, but the impact may last longer given their existing metabolic impairment. One study at Duke University looked at how consuming the caffeine equivalent of about five cups of coffee—half at breakfast, half at lunch—impacted participants’ glucose levels throughout the day. It found that caffeine raised their glucose responses to breakfast, lunch, and dinner, as well as causing an increase in their overall average glucose for the day. 

Similarly, a study in women with gestational diabetes showed that even doses below the recommended safe amount of caffeine for pregnant women (200 mg, or about two cups) led to a short-term decrease in insulin sensitivity.

There’s increasing evidence that genetics play a role in how different people process caffeine, too. Researchers refer to “fast metabolizers” and “slow metabolizers,” who show differences in how caffeine affects their glucose and insulin levels. A study published at the end of 2020 looked at the effects of caffeine energy shot drinks in adolescents. It found that not only did the drinks disrupt teens’ glucose metabolism and insulin sensitivity, there were also significant differences among the subjects that seemed to correlate with genetic differences. Those who metabolized caffeine the quickest had the poorest glucose and insulin responses. Earlier research theorized that people who clear caffeine rapidly never get a chance to build their caffeine tolerance, but there’s still no consensus on whether people even can build a tolerance to all of caffeine’s effects in the body.

As for decaf, some studies show that it causes the same decrease in insulin sensitivity that regular coffee does, but to a lesser degree. Researchers suggest that may be because even decaf usually has traces of caffeine. 

Why Caffeine Impacts Glucose and Insulin

But why does caffeine impair glucose metabolism? Caffeine stimulates the central nervous system by blocking the action of adenosine, a metabolite that helps regulate our energy levels. 

Does Caffeine Raise Blood Sugar? - by Dr Sam Robbins

In the brain, adenosine acts as a neurotransmitter and promotes restful sleep by tamping down the activity of neurostimulators like dopamine. Caffeine can bind to adenosine receptors in the brain, preventing adenosine from binding at those sites and curbing its ability to inhibit dopamine. The effect: we feel more alert. Scientists have found genetic variation in those adenosine receptors among different people, which may explain why individual responses to caffeine vary. 

The reason adenosine affects glucose is that in addition to the brain, there are adenosine receptors throughout the body, including in adipose (fat) tissue and muscle tissue—both sites where insulin facilitates glucose uptake—as well as in the liver, which controls the production of glucose and release of stored glucose. Scientists still aren’t precisely sure which adenosine receptors play the most crucial role in modifying glucose uptake and insulin sensitivity. But a recent animal study suggests its effect on muscle tissue uptake exerts the most significant influence. Either way, multiple studies demonstrate that restricting the action of adenosine, as caffeine has been shown to do, decreases insulin sensitivity.

In addition, when the liver metabolizes caffeine, most of it is broken down into a metabolite called paraxanthine, which studies show is also a potent inhibitor of adenosine. This may account for the fact that caffeine’s effects on insulin can last longer than its short half-life in the body would suggest.   

Caffeine also increases the amount of epinephrine (aka adrenaline) circulating in the blood, which accounts for part of the energy boost you feel after imbibing. Epinephrine is also known to cause insulin resistance, impair glucose control, and trigger glucose production. However, studies have shown that in the small amounts triggered by caffeine, epinephrine’s impact on glucose is probably too low to be responsible for caffeine’s effects.    

The Long Term: Drinking Coffee Lowers Type 2 Diabetes Risk

If caffeine’s negative short-term effect on glucose metabolism is well established, so is coffee’s desirable impact on the risk of Type 2 diabetes. That coffee lowers one’s risk of developing diabetes has been confirmed in multiple reviews, as well as in large population studies. 

One study, which followed nearly 1900 adult men and women for a median duration of 5.8 years, found that adults who consumed at least one cup of coffee per week had a 22% lower risk for prediabetes and 34% risk reduction for Type 2 diabetes compared to people who didn’t drink coffee. Another study, which followed around 88,000 women in the US with no history of diabetes, found that both regular and decaf coffee consumption for eight years seemed to lower the risk of developing Type 2 diabetes, with regular coffee offering a slight edge over decaf. Drinking more cups was associated with lower risk—women who drank one cup per day saw a 13% reduction in relative risk, while women who drank four or more cups saw a 47% reduction.

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That decaf demonstrates nearly the same benefits as regular coffee suggests that something other than caffeine is driving the protective effect. The most likely candidate is chlorogenic acids, members of a group of antioxidant-rich micronutrients called polyphenols, abundant in plant-based foods. 

Studies of chlorogenic acids and their derivatives suggest that they play a significant role in glucose and lipid metabolism and may effectively combat diabetes, metabolic syndrome, and high blood concentrations of fats, including cholesterol. Researchers have even investigated them as a source of new treatments for Type 2 diabetes. 

Chlorogenic acids may improve glucose metabolism in several ways, according to studies in animals and cell lines:

Inhibiting G6Pase, a protein that regulates glucose production in the liver and its release into the blood.

Reducing intestinal absorption of glucose

Stimulating glucose uptake by fat and muscle tissues

Providing antioxidant and anti-inflammatory protection

Improving insulin sensitivity in peripheral tissue

In short, the positive impacts of chlorogenic acids on glucose metabolism outweigh the adverse effects of caffeine. While caffeine may decrease insulin sensitivity in the short term, which could increase the typical post-meal glucose spike, the multiple actions of chlorogenic acids in coffee appear to reduce the total glucose impact from that meal, as well as provide long-term benefits like protection against oxidative stress and inflammation, which can contribute to Type 2 diabetes.    

A 2006 randomized, double-blind study seemed to back up this idea. It compared the metabolic responses of participants given either decaf coffee, regular coffee, a caffeine capsule, or a placebo, followed by an oral glucose tolerance test. It found a 50% lower glucose response in the decaf group compared to the placebo group, and a 40% lower response in the regular coffee group compared to the pure caffeine group. Since all participants ingested the same amount of glucose, these results suggest there are compounds in coffee that either slow glucose absorption or increase glucose uptake in bodily tissues. 

Coffee Alternatives

Not a coffee fan? A 2020 meta-analysis found that taking a supplement with 400 mg or more of green coffee bean extract positively affected both fasting blood sugar and insulin levels. 

Green tea may also confer metabolic benefits due to polyphenols—not chlorogenic acids this time, but antioxidant compounds called catechins, which may also regulate glucose uptake in the gut. One study found that people with Type 2 diabetes who drank four cups of green tea a day for two months experienced significant weight reduction, waist circumference, and systolic blood pressure. What’s more, the anti-diabetic effects of polyphenols found in green tea, including improved glucose tolerance, have been supported by studies in animals and humans.

So What Should You Do? 

If caffeine is part of your current routine, either in your morning coffee or before a workout, be aware that it is likely decreasing your acute insulin sensitivity. Try not to pair it with high-carb meals.

Given that the apparent benefits of long-term coffee consumption appear to outweigh the short-term effects (at least on glucose metabolism), you probably don’t need to cut it out.

Switching to decaf appears to offer many of the same benefits but with a lesser short-term effect than regular coffee. 

If you’re not a coffee person, don’t start drinking coffee just for the long-term metabolic benefits. You can get the same beneficial chlorogenic acids through several fruits and vegetables, including apples, artichokes, carrots, and tomatoes. Drinking green tea also appears to have long-term positive effects.

Remember to avoid adding sugar or artificial sweeteners to your coffee, and skip the sugary energy drinks. 

The average U.S. adult drinks about two 8-ounce (240-milliliter) cups of coffee a day, which can contain around 280 milligrams of caffeine. For most young, healthy adults, caffeine doesn't appear to noticeably affect blood sugar (glucose) levels, and having up to 400 milligrams a day appears to be safe.

Foods that Help with Insulin (sensitivity and resistance)

Some studies suggest that drinking coffee — whether caffeinated and decaffeinated — may actually reduce your risk of developing type 2 diabetes.

If you already have diabetes, however, the impact of caffeine on insulin action may be associated with higher or lower blood sugar levels. For some people with diabetes, about 200 milligrams of caffeine — or the equivalent of one to two 8-ounce (240-milliliter) cups of plain, brewed coffee — may cause this effect.

Caffeine affects every person differently. If you have diabetes or you're struggling to control your blood sugar levels, limiting the amount of caffeine in your diet may provide a benefit.

How do you bring your blood sugar down quickly?

When your blood sugar level gets too high — known as hyperglycemia or high blood glucose — the quickest way to reduce it is to take fast-acting insulin. Exercising is another fast, effective way to lower blood sugar.

In some cases, you should go to the hospital instead of handling it at home.

Very high blood sugar levels can result in diabetic ketoacidosis (DKA) when insulin levels are low. This is a medical emergency.

Symptoms of DKA include:

shortness of breath

breath that smells fruity

nausea and vomiting

a very dry mouth

If you aren’t sure what to do, call your doctor to get instructions on administering a dose of insulin, and for advice about whether to go to the emergency room.

This article looks at ways to lower your blood sugar quickly, when to go to the emergency room or see a doctor, and tips for managing high blood sugar.

Best ways to lower blood sugar quickly

When treated early, you can bring high blood sugar levels down and prevent complications, including DKA.

Some sources suggest that drinking water or eating a high protein snack can quickly lower your blood sugar levels, though there isn’t enough research to support this.

If you have high blood sugar and need to lower it fast, try the following methods:

Take your insulin as prescribed

High blood sugar occurs when your body has too little insulin, or your body can’t use insulin properly. Administering insulin can bring your blood sugar levels down.

Talk to your doctor about how much rapid-acting insulin you should administer when your blood sugar is high.

Three Ingredients You Should Never Add to Your Coffee

You may want to check your blood sugar about 15–30 minutes after taking insulin to make sure your blood sugar is going down and that it’s not dropping too low.

Exercise

Exercise is a fast and effective way to lower your blood sugar levels.

Exercise can lower your blood sugar for 24 hours or more after you’ve finished. This is because it makes your body more sensitive to insulin.

Physical activity causes the body to demand glucose for energy. As a result, the cells deliver glucose to the muscles and blood sugar levels usually drop.

For this to work, you need a form of exercise that gets your heart pumping faster than usual. This can include walking at a quick pace.

Importantly, if your blood sugar is above 240 mg/dl, you should check your urine for ketones. If ketones are present, do not exercise, because this can make your blood sugar rise even higher.

Exercising when you have ketones in your urine increases your risk of complications from high blood sugar.

If you have type 1 diabetes, your doctor will likely recommend you check your blood sugar before exercising. You can do this with at-home urine ketone testing kits, which are available online.

While exercise is an effective way to lower your blood sugar throughout the day, some types of exercises — particularly short bursts of strenuous activity — can briefly increase blood sugar levels.

This is because strenuous activity activates the body’s stress response, causing a release of glucagon to power the muscles.

If your ketone levels are high, avoid strenuous exercise and try some light exercise, like walking, instead.

SUMMARY

Exercising can usually bring down high blood sugar levels, but don’t exercise if there are ketones in your urine. Talk to your doctor about whether you should take insulin to treat hyperglycemia.

Does coffee raise blood sugar Type 1?

Have you ever noticed a difference in your blood sugar after drinking a cup of caffeinated coffee or tea? According to the Mayo Clinic, caffeine can indeed have an affect on your blood sugar levels causing lower or higher fluctuations. Being mindful of how much caffeine you consume will make blood sugar management easier.

The Ugly Truth About Coffee’s Effects On Your Body

Another study published by the ADA (2005) suggests that people with Type 1 or Type 2 diabetes can reduce their risk of hypoglycemia during the night by having a small to moderate amount of caffeine before bed. Some people also claim that symptoms of hypoglycemia become more noticeable when incorporating caffeine into their diet.

The effects of caffeine can vary from person to person based on your body’s sensitivity to the stimulant. Some people report noticeable effects of caffeine on their blood sugar levels while others see little or not impact at all.

Let’s explore some variables that could contribute to the shift in BG levels in relation to caffeine consumption.

WHY CAFFEINE CAN SPIKE YOUR BLOOD SUGAR

We often think that it’s the caffeine itself that gives us energy when we drink a cup of coffee, tea, or soda, but it’s actually related to what the caffeine triggers hormonally in our body.

Caffeine is a stimulant that tells gives you energy through a variety of ways, explains Science Direct:

Caffeine blocks “adenosine receptors” from binding to your cells. Normally, these receptors bind to your cells to help you fall alseep, by blocking this bind, caffeine is increasing cell activity.

Caffeine also increases your effects of other natural stimulants produced by your brain: serotonin, dopamine, and acetylcholine. These all give you an extra boost!

Caffeine increases your body’s release of adrenaline. And this is why caffeine can raise your blood sugar.

We also tend to think of adrenaline as something that simply gives us energy, but like caffeine, it’s more complicated than that! Instead, adrenaline actually triggers your liver to release stored glucose, giving you the fuel you need to endure a soccer game, a rollercoaster ride, or your usual Monday morning.

(Adrenaline also tells your heart to beat faster and improves your muscles’ ability to contract.)

For some people, a cup of coffee in the morning may cause no spike at all, but if you consume 2 or 3 cups, you surpass your body’s tolerance for caffeine and see a stubborn and steep rise in your BG. Another variable might be when you drink caffeine. Your body may tolerate it find in the morning, but a single cup of coffee in the afternoon sends your BG soaring. Take good notes to pinpoint how your body reacts to caffeine.

IT MIGHT NOT BE THE CAFFEINE SPIKING YOUR BG

Certain common side-effects of caffeine consumption may often explain shifts in BG levels.

Is Coffee Good For Diabetes?

LACK OF SLEEP

Not enough sleep has proven to contribute to insulin resistance in the body for people with Type 1. Too much caffeine could certainly contribute to insomnia, especially since caffeine tolerance decreases as we grow older.

ELEVATED HEART RATE / “THE JITTERS”

Two common effects if too much caffeine is in the system, or if the body is not accustomed to it. These are also symptoms of hypoglycemia, which might cause someone with Type 1 to check their BG levels more frequently if mistaking the symptoms for a low.

HEARTBURN / UPSET STOMACH / DEHYDRATION

Some people are less tolerant to coffee and other caffeinated beverages than others, so these symptoms can often occur. The body’s hormonal responses from these symptoms (and feeling ill in general) can always cause BG levels to rise and fall.

DAWN PHENOMENON

The dawn phenomenon (or “dawn effect”) is the term used to describe an abnormal rise in BG levels in many people, between the hours of approximately 2 a.m. and 8 a.m. Most researchers believe this effect to be the result of hormone surges – the body’s overnight release of cortisol, glucagon and epinephrine, which all increase insulin resistance. Of course, the phenomenon could also be in part due to management factors such as high carb consumption before bedtime or insufficient insulin dosages. Nevertheless, we could very well be inaccurately accusing caffeine of morning BG spikes, but in reality, the dawn phenomenon is the actual cause.

SWEETENERS

Of course, if you plan on sweetening your caffeinated beverage with sugar, cream or milk, always check the carb count and bolus or take your injections accordingly! Even some artificial sweeteners have been known to cause a rise in BG levels due to its ingredients.

So – what is the takeaway from all of this? Everyone’s body reacts differently to foods and beverages – Type 1 or no Type 1! It is important to keep in mind that studies thus far on caffeine and BG levels remain inconsistent. Knowing exactly how much affect it could have on you will take some experimentation, and could be dependent on many things – including time of day, carb counts, physical activity, hormone levels and the amount of caffeine ingested.

Can you drink black coffee before a blood glucose test?

I heard the same question almost every time I gave pre-op instructions to a patient: Once I got to the part about “nothing to eat or drink after …”, nearly every one of them would look at me in anguish and ask, “Does that mean no coffee??”

Coffee and Diabetes - Can Coffee Increase Your Blood Sugar?

I feel you.

As a connoisseur of caffeine, myself, I understand that fasting can be difficult enough without giving up coffee to do it. And the good news is: sometimes you don’t have to!

SLIDESHOW

Health Benefits of Coffee and Tea

Reviewed by Christine Mikstas on 21.4.2021

The answer to this question depends on the type of fasting you’re doing. Can you drink coffee while doing …

Pre-surgical fasting? No, you absolutely may not drink coffee (or water – or beverages of any kind) after the cut-off time you’re given. That’s because the medications used in general anesthesia make it easy for stomach contents to regurgitate into the esophagus, where they can be inhaled. Not good. So, you should never eat or drink anything for several hours prior to a surgery with general anesthesia.

Fasting before blood tests? Yes, in most cases, you may drink black coffee before a “fasting” blood test (or black tea if that’s your preference). These beverages generally will not affect the results of common fasting lab tests, like cholesterol (lipid panel), metabolic panel or blood glucose. To be safe, though, you should ask your doctor or call the lab in advance to see if you can enjoy your morning java fix before you get your blood drawn. And what happens if you cheat and add cream or sugar to your coffee before a fasting lab test? Well, it can greatly alter the results, so be sure to alert the lab tech and your doctor. You may be asked to have the blood drawn all over again.

Intermittent fasting? Yes, you can drink black coffee (or tea or pretty much any non-caloric beverage) if you’re doing intermittent fasting (IF). IF is based on a concept called “time-restricted feeding” in which you take in calories only during a small window of time each day. But black coffee does not contain calories, so drinking it won’t break your fast. Now, if you add cream or sugar, then you’ve blown your fast because those things contain calories.

When you’re asked to fast for medical reasons, it’s important to follow your doctor’s specific instructions – even if that means no coffee – because breaking the fast could seriously jeopardize your health. But if you’re fasting to lose weight or just because you think it’s a healthier lifestyle, you don’t have to give up coffee. In fact, you can consider it a little indulgence that might help you get through the fasting period more easily!

Can black coffee make your blood sugar go up?

Whether it’s from coffee, tea, soda, or chocolate, most Americans get caffeine every day. For healthy people, it’s usually a harmless perk-me-up. But if you have type 2 diabetes, caffeine may make it harder to keep your blood sugar in check.

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How Does Caffeine Affect Your Blood Sugar?

A growing body of research suggests people with type 2 diabetes react to caffeine differently. It can raise blood sugar and insulin levels for those with the disease.

One study looked at people with type 2 diabetes who took a 250-milligram caffeine pill at breakfast and another at lunchtime. That’s about the same amount as drinking two cups of coffee with each meal. The result: Their blood sugar was 8% higher than on days when they didn’t have caffeine. Their reading also jumped by more after each meal.

That’s because caffeine can affect how your body responds to insulin, the hormone that allows sugar to enter your cells and get changed into energy.

Caffeine may lower your insulin sensitivity. That means your cells don’t react to the hormone by as much as they once did. They don’t absorb as much sugar from your blood after you eat or drink. This causes your body to make more insulin, so you have higher levels after meals.

If you have type 2 diabetes, your body already doesn’t use insulin well. After meals, your blood sugar rises higher than normal. Caffeine may make it tougher to bring it down to a healthy point. This may lead to too-high blood sugar levels. Over time, this may raise your chance of diabetes complications, like nerve damage or heart disease.

Why Does Caffeine Have This Effect?

Scientists are still learning how caffeine affects your insulin and blood sugar levels. But they think it may work this way:

Caffeine raises levels of certain stress hormones, like epinephrine (also called adrenaline). Epinephrine can prevent your cells from processing as much sugar. It may also keep your body from making as much insulin.

It blocks a protein called adenosine. This molecule plays a big role in how much insulin your body makes. It also controls how your cells respond to it. Caffeine keeps adenosine which plays a big role in how much insulin your body makes.

It takes a toll on your sleep. Too much caffeine can keep you awake. Lack of sleep may also lower your insulin sensitivity.

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How Much Caffeine Is Too Much?

It only takes about 200 milligrams of caffeine to affect your blood sugar. That’s the amount in about one or two cups of brewed coffee or three or four cups of black tea.

You may be able to handle more or less caffeine. People can have different reactions to the drug. Your response depends on things like your age and weight.

How much caffeine you usually get may also play a role. People with diabetes who are regular coffee drinkers don’t have higher blood sugar levels than those who aren’t. Some experts think your body gets used to that amount of caffeine over time. But other research shows that caffeine could still cause a spike, even if you always start your day with a cup of joe.

To find out if caffeine raises your blood sugar, talk to your doctor or a dietitian. You might test your blood sugar throughout the morning after you have your usual cup of coffee or tea. Then you’ll test after you skip the drink for a few days. When you compare these results, you’ll know if caffeine has an impact.

What About the Caffeine in Coffee?

There’s another twist to the story. Studies show that coffee may lower your odds of getting type 2 diabetes in the first place. Experts think that’s because the drink is high in antioxidants. These compounds reduce inflammation in your system, which can raise your chance of having the disease.

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If you already have type 2 diabetes, this may not hold true. The caffeine in a cup of java makes it tougher to control your blood sugar. If yours spikes after your morning cup, you may want to switch to decaf. Even though this drink has a tiny amount of caffeine, it doesn’t have the same effect on your blood sugar or insulin.

While coffee and caffeine have been shown to possibly prevent the condition in people who don’t already have it, that morning cup of Joe could have some serious effects on your diabetes.

The Science

According to WebMD, caffeine can impair insulin reaction. This means it may take more time for your dose of insulin to fully kick in. Caffeine can also increase your body’s resistance to insulin. This can ultimately lead to high blood sugar levels and to further diabetes complications.

In addition, a 2008 Duke University study showed that caffeine may have an impact on your blood glucose levels. The study examined people with type 2 diabetes. One group of participants took 500 mg caffeine–about the equivalent of about two cups of coffee–every day for a week, while the second group abstained from caffeine. Each person’s blood glucose levels were tested multiple times throughout the week, and it was found that those who drank caffeine had blood sugars around 8 percent higher than those who didn’t take caffeine.

Alternative Solutions

So, what’s the best option for people with diabetes who still want their coffee fix? Try making your order decaf. It’s also best to avoid added creamers, syrups and sweeteners. If you’re really craving some extra flavor, opt for the sugar-free varieties. And make sure you say no-thanks to the mile-high swirl of whipped cream that tops most coffeehouse favorites. It can be so difficult to make good habits according to your diabetes, but it is so important!

Does Black Coffee Break a Fast? Research & Test

Options for your next order:

Decaf black coffee

Caffeine-free herbal tea

Low-fat smoothie (just make sure to check the sugar content)

Small decaf latte with skim or soy milk

Coffee Shop

SUMMARY

If coffee is a necessity to get a kick-start to your day, make sure it isn’t impacting your sugar levels too much. Try to order decaf and avoid the added creamers, syrups and sweeteners. This way, you can get your coffee fix and keep your sugar levels under control!