Does caffeine affect blood sugar?
Answer From M. Regina Castro, M.D.
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.
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.
M. Regina Castro, M.D.
April 12, 2022
From Mayo Clinic to your inbox
Sign up for free, and stay up to date on research advancements, health tips and current health topics, like COVID-19, plus expertise on managing health.
ErrorEmail field is required
ErrorInclude a valid email address
To provide you with the most relevant and helpful information, and understand which
information is beneficial, we may combine your email and website usage information with
other information we have about you. If you are a Mayo Clinic patient, this could
include protected health information. If we combine this information with your protected
health information, we will treat all of that information as protected health
information and will only use or disclose that information as set forth in our notice of
privacy practices. You may opt-out of email communications at any time by clicking on
the unsubscribe link in the e-mail.
Thank you for subscribing!
You'll soon start receiving the latest Mayo Clinic health information you requested in your inbox.
Sorry something went wrong with your subscription
Please, try again in a couple of minutes
See more Expert Answers
- Bordeaux B, et al. Benefits and risks of caffeine and caffeinated beverages. https://www.uptodate.com/contents/search. Accessed Dec. 6, 2019.
- Dewar L, et al. The effect of acute caffeine intake on insulin sensitivity and glycemic control in people with diabetes. Diabetes and Metabolic Syndrome: Clinical Research & Reviews. 2017; doi:10.1016/j.dsx.2017.04.017.
- Emami MR, et al. Acute effects of caffeine ingestion on glycemic indices: A systematic review and meta-analysis of clinical trials. Complementary Therapies in Medicine. 2019; doi:10.1016/j.ctim.2019.05.003.