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Can Caffeine Affect A1C Levels?

author image Dr. Tina M. St. John
Tina M. St. John runs a health communications and consulting firm. She is also an author and editor, and was formerly a senior medical officer with the U.S. Centers for Disease Control and Prevention. St. John holds an M.D. from Emory University School of Medicine.
Can Caffeine Affect A1C Levels?
A large cup of coffee. Photo Credit: Jack Hollingsworth/Blend Images/Getty Images

Blood glucose control is the cornerstone of diabetes management. Your A1C level reflects your glucose control over the previous two to three months, with high levels indicating poor control. Many factors affect your A1C level, including your diet, medications and physical activity level. Research data indicate that caffeine consumption temporarily interferes with normal glucose metabolism, which might affect your blood sugar and A1C levels.

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Increased Insulin Resistance

Diabetes occurs when your pancreas fails to produce sufficient insulin or, more commonly, your cells resist the effects of insulin. Insulin resistance leads to high blood sugar levels because glucose remains in your bloodstream rather than moving into your cells or going into storage. Type 2 diabetes is primarily a disease of insulin resistance. Caffeine causes a temporary increase in insulin resistance, which means your cells take up less glucose when you consume caffeine. In a 2008 article published in the journal "Diabetes Care," James Lane, Ph.D., and colleagues report that the average daily glucose level among study participants ingesting 500 milligrams of caffeine — roughly the amount in four 8-ounce cups of coffee — was approximately 11 milligrams per deciliter higher than in those who did not consume caffeine.

Dietary Sources of Caffeine

Caffeine is present in many common foods and beverages. Some you are probably aware of, but others might surprise you. Regular coffee, black tea and colas are leading sources of dietary caffeine for many Americans. Regular green and white teas also contain caffeine. Pepper-type and citrus sodas typically contain caffeine; in some cases, the levels are higher than the amounts found in popular colas. Some manufacturers of root beer, cream soda and orange soda add caffeine to the beverages. Energy drinks and caffeinated sports drinks are an increasingly common source of dietary caffeine. Chocolate bars, coffee- and chocolate-flavored frozen desserts, and caffeinated gum and breath mints also contribute to your daily caffeine intake.


Several over-the-counter medications contain caffeine. Certain headache and menstrual remedies combine caffeine with aspirin, acetaminophen or both to enhance pain relief. Similarly, many weight-loss products and a few cold-relief medicines contain caffeine. Caffeine is the primary active ingredient in nonprescription products to promote "alertness." Read the ingredients if you are uncertain whether a product contains caffeine.

What to Do

As of publication, there are no formal guidelines recommending that you eliminate caffeine from your diet if you have diabetes or prediabetes, but if you consume large amounts of caffeine daily and have trouble controlling your blood sugar level, reducing or eliminating caffeine might be worthwhile. Talk with your doctor about whether adjusting your caffeine intake might be beneficial for you.

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