Woman checking blood sugar levels with fingerstick glucometer

Does caffeine affect blood sugar?

Medically reviewed on October 4, 2022 by Jordan Stachel, M.S., RDN, CPT. To give you technically accurate, evidence-based information, content published on the Everlywell blog is reviewed by credentialed professionals with expertise in medical and bioscience fields.

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According to a recent study, the average American relies on three cups of coffee to help them power through each day. [1] If you, too, turn to java every morning, you’ve likely experienced some of the negative side effects associated with excessive caffeine consumption firsthand: shakiness, dehydration, and a creeping dependency, to name a few.

However, if you have diabetes, caffeine can have other side effects that are far less talked about but can potentially be more dangerous. The average healthy young adult can get away with a few shots of espresso every day, but if you have type 2 diabetes, caffeine may hinder your ability to keep your blood sugar levels in check.

If you’re wondering whether your caffeine intake might adversely affect your blood sugar levels and how to lower your HbA1c, keep reading. Below, we’ll talk about caffeine’s impact on blood sugar levels, who is at risk, and common sources of caffeine to watch out for.

The effects of caffeine on blood sugar

Does caffeine affect blood sugar levels? The short answer is yes. You might think that since black coffee—free from sweeteners, milk, and sugar—doesn’t contain any carbohydrates it shouldn’t raise blood sugar levels on its own. However, one study found that acute caffeine ingestion with meals led to increased insulin and blood glucose levels and a decrease in insulin sensitivity. [2]

When you consume carbohydrates, the amount of sugar in your blood goes up. In response, your pancreas releases insulin into your bloodstream, helping to regulate the increase in blood sugar. This is all part of the normal process that allows your body to turn sugar into energy and/or to store it for later use.

But some of us experience “insulin resistance” due to diet, weight, and a variety of other factors. This is when our cells have trouble responding to insulin and absorbing glucose to use as fuel. As a result, the pancreas begins overproducing insulin. This creates a buildup of sugar in the blood that can eventually lead to type 2 diabetes. [3]

The study mentioned above found that caffeine causes a short-term decrease in insulin sensitivity (or an increase in insulin resistance). In this situation, caffeine intake can inhibit the body’s ability to regulate blood glucose levels, impairing the effectiveness of insulin and exacerbating diabetes.

This might sound scary to those with type 2 diabetes, but it shouldn’t put you off caffeine entirely. If you’re concerned about caffeine consumption negatively impacting your body’s ability to utilize glucose in the bloodstream, try consuming your morning coffee after you’ve eaten breakfast. Or, grab that diet coke after you’ve already had lunch. By consuming caffeine postprandial, you have given your body other macronutrients like protein and fat that help to mediate the response that caffeine has on blood sugar levels, helping to prevent them from spiking.

For those with type 2 diabetes, the effects of caffeine on blood glucose levels can last longer, given the existing resistance to insulin that comes with that condition. [4] However, caffeine is generally safe for others to consume, as long as it isn't overused.

Should diabetics avoid coffee?

The information above raises the question of whether diabetics should avoid coffee entirely. After all, anything that decreases insulin sensitivity and increases glucose levels is bad, right?

If you already have diabetes and don’t drink coffee, it’s probably a good idea to avoid developing the habit. Depending on why you might turn to coffee, there are alternatives out there that are safe, easy to source, and inexpensive. Some of them are even better for your health and wellness. If you can’t give up the flavor, perhaps try decaffeinated coffee first—just remember that there is still some caffeine present, only less.

If you developed diabetes after already becoming dependent on coffee to help fuel your day, there is one very important and simple step you can take to limit its negative effects on your blood sugar levels: avoid additives and sweeteners.

Additives and sweeteners for diabetics to avoid

Coffee creamers and flavored syrups are often loaded with sugars and carbohydrates, which place a heavy strain on your body as it tries to produce and use insulin to clear sugar from the bloodstream. Some examples include:

  • Creamers
  • Artificial flavors, like hazelnut or vanilla syrups
  • Artificial sweeteners
  • Cane sugar
  • Condensed milk
  • Corn syrup
  • Hydrogenated oils

We recognize that the barista at your local coffee shop is unlikely to add hydrogenated oils to your favorite morning beverage. But many of these ingredients to avoid can be found in the syrups and sweeteners used by coffee shops, especially at chains like Starbucks and Dunkin' Donuts.

If you’re making coffee at home, always check the labels of any products you add to your drink. If ordering at a coffee shop before heading to work in the morning, request nutritional information on the products offered or try searching for it online.

Remember, our rule of thumb is that if you have diabetes and decide to continue drinking coffee, it's best to take it black.

Other caffeine sources to monitor

Though it isn’t often discussed, coffee, energy drinks, and other sources of caffeine can negatively impact our blood sugar levels by reducing insulin sensitivity. To make matters worse, these drinks are often loaded with sugars and carbohydrates, which spike blood glucose even more.

How much caffeine is too much caffeine?

According to the FDA, most Americans can drink up to 400 milligrams of caffeine every day without adverse effects. [5] This comes out to about 4 or 5 cups per day—more than what the average coffee drinker consumes daily.

That said, this is a ballpark number, and some people may benefit from consuming significantly less caffeine. In addition to people with type 2 diabetes, these groups include:

  • Women who are pregnant and/or breastfeeding
  • Teenagers and adolescents
  • People impacted by sleep disorders
  • People with arrhythmias
  • People who struggle with anxiety

However, these groups aren’t at risk from too much caffeine just because of blood glucose levels. For example, caffeine increases the amount of epinephrine (otherwise known as adrenaline) in the bloodstream. This can be bad news for people who deal with the jitters or nervousness.

There are ways to offset the negative effects of caffeine, however, depending on how it affects your body. If you struggle to regulate your blood glucose levels, try consuming less than 200 milligrams daily. If you have trouble sleeping, switch to caffeine alternatives in the afternoon and avoid consuming caffeine until the next morning.

Where does caffeine come from?

While most of us think of coffee and caffeine as synonymous, the truth is that coffee contains less caffeine than many other foods and beverages we regularly consume. One study found that caffeine is used as a flavor enhancer in over 60% of soft drinks sold in the United States. [6]

Some common sources of caffeine include:

  • Tea
  • Chocolate
  • Guarana
  • Energy drinks
  • Analgesics (pain relievers)

Caffeine is also present in small amounts in decaf coffee, despite what its name may lead us to believe.

Healthy alternatives to caffeine

Packaged foods and drinks—such as energy drinks, chocolate bars, or dietary supplements that contain caffeine—often provide information about their caffeine content on the nutritional label. For some people, this can help them to regulate their intake. Others can go by how they feel—shaky hands, feelings of dread, and racing thoughts are signs to back off the caffeine until your body processes it.

For those worried about caffeine spiking their blood glucose levels, or anyone who is looking for a non-caffeinated way to kickstart the morning, there are many alternatives to caffeine that can give you a little boost without the negative side effects.

B vitamins

All cells in the body use B vitamins, which are found in lean protein, healthy fat, and whole grain sources such as:

  • Turkey
  • Nuts and seeds
  • Fish
  • Whole grains

While there are eight different kinds of B vitamins, any of them can help our bodies convert food into energy, rev up the metabolism, and protect us against anemia.


A vegan chocolate alternative, this caffeine-free superfood is nutrient-dense and includes protein and vitamins A and B. Carob also contains pinitol, a natural compound that has an insulin-like effect shown to reduce glucose concentrations in diabetic lab rats. [7]


The main ingredient in the trendy “golden milk” that originated in India and is fast becoming a staple of coffee shops here in the U.S. is turmeric, which is full of anti-inflammatory properties and nutrients. It’s also caffeine free, which makes it a wonderful alternative for those who enjoy the ritual and warmth of a morning cup of joe.

If you turn to coffee in the morning as part of your routine, replacing it with a hot, turmeric-based drink is an excellent way to decrease the negative impacts of caffeine while still reaping the mental health benefits of indulging in a delicious morning beverage.

Monitor your blood sugar levels to understand your body's glycemic control

If you’re struggling to control your blood sugar levels thanks to diabetes or other health issues, our HbA1c Test can help you manage your health better by providing an average of your blood sugar levels over the past 90 days.

Routine glucose tests can equip you with the personal knowledge you need to make healthier choices that positively impact your blood glucose levels. And with a longer testing period, results will help you determine better baselines and track long-term progress.

Head to our site to order an HbA1c Test or visit our blog to learn more about the science behind our products.

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  1. The Atlas of American Coffee. 2021 National Coffee Data Trends: www.ncausa.org. URL. Accessed September 30, 2022.
  2. Shi X, Xue W, Liang S, Zhao J, Zhang X. Acute caffeine ingestion reduces insulin sensitivity in healthy subjects: a systematic review and meta-analysis. Nutrition Journal. 2016;15(1). doi:10.1186/s12937-016-0220-7. Accessed September 30, 2022.
  3. Type 2 Diabetes. CDC. Published December 16, 2021. URL. Accessed September 30, 2022.
  4. Whitehead N, White H. Systematic review of randomised controlled trials of the effects of caffeine or caffeinated drinks on blood glucose concentrations and insulin sensitivity in people with diabetes mellitus. Journal of Human Nutrition and Dietetics. 2013;26(2):111-125. doi:10.1111/jhn.12033. Accessed September 30, 2022.
  5. Spilling the Beans: How Much Caffeine is Too Much? U.S. Food and Drug Administration. Published December 12, 2018. URL. Accessed September 30, 2022.
  6. Keast RSJ, Riddell LJ. Caffeine as a flavor additive in soft-drinks. Appetite. 2007;49(1):255-259. doi:10.1016/j.appet.2006.11.003. Accessed September 30, 2022.
  7. Bates SH, Jones RB, Bailey CJ. Insulin-like effect of pinitol. British Journal of Pharmacology. 2000;130(8):1944-1948. doi:10.1038/sj.bjp.0703523. Accessed September 30, 2022.
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