Coffee and blood sugar is a topic where two kinds of research get mixed together: short-term studies of what caffeine does in the hours after you drink it, and long-term population studies that follow coffee drinkers for years. They answer different questions. This page walks through what each kind of research has found about coffee in general, what it can't tell you, and how to read the sugar lines on a coffee label.
What Long-Term Studies Have Found
The largest pooled analysis is a 2014 dose-response meta-analysis in Diabetes Care by Ding and colleagues (full text). It combined 28 prospective studies with 1,109,272 participants and 45,335 cases of type 2 diabetes. Compared with people who drank no coffee or rarely drank it, the relative risk of type 2 diabetes was:
| Cups of coffee a day | Relative risk (vs. none or rare) |
|---|---|
| 1 | 0.92 |
| 2 | 0.85 |
| 3 | 0.79 |
| 4 | 0.75 |
| 5 | 0.71 |
| 6 | 0.67 |
Each additional daily cup was associated with about a 9% lower risk for caffeinated coffee and about a 6% lower risk for decaf. The authors found the difference between caffeinated and decaf was not statistically significant. Their conclusion: coffee consumption was inversely associated with the risk of type 2 diabetes in a dose-response manner.
A second Harvard analysis, published in Diabetologia in 2014 by Bhupathiraju and colleagues (full text), looked at people whose coffee habits changed. Across three large US cohorts (the Nurses' Health Study, Nurses' Health Study II and the Health Professionals Follow-up Study) with 7,269 cases of type 2 diabetes:
- People who increased their coffee intake by more than 1 cup a day over 4 years had a 12% lower risk of type 2 diabetes over the next 4 years, compared with people whose intake didn't change.
- People who cut back by more than 1 cup a day had an 18% higher risk.
- Changes in decaf intake were not associated with risk, which the authors partly put down to how few people made large changes in decaf.
In July 2026, the American Heart Association's scientific statement on caffeine also noted that caffeinated coffee is linked to a lower risk of type 2 diabetes (AHA summary).
All of these are associations from observational research. Association doesn't show that coffee caused the lower rates.
What These Studies Can't Tell You
The AHA points out that most caffeine research is observational, so confounding is a major concern: coffee drinkers may differ from non-drinkers in ways the studies can't fully measure (AHA summary). It also notes that responses to caffeine vary widely with genetics, habitual intake, age and existing conditions. Population averages don't predict how any one person will respond.
Short-Term Effects of Caffeine
The short-term picture runs the other way. According to the AHA's news release, research suggests that caffeinated coffee may reduce insulin sensitivity in the short term. The same release says that drinking black, caffeinated coffee with no additives, flavors or sweeteners regularly was linked to a lower risk of type 2 diabetes. Both findings can be true at once, because they measure different things over different time spans.
If you have diabetes or prediabetes, or you're managing your blood sugar with a doctor, ask them how caffeine fits your situation.
Plain Coffee vs. Coffee Drinks
Many coffee drinks are more than coffee. The AHA says adding sugar, flavored syrups, milk or cream to coffee likely reduces whatever health effects plain coffee may have (AHA).
Added sugar is the line worth checking. According to the FDA:
- The Daily Value for added sugars is 50 grams per day, based on a 2,000 calorie diet.
- The Dietary Guidelines for Americans recommend limiting calories from added sugars to less than 10 percent of total calories per day.
- For most Americans, the main sources of added sugars are sugar-sweetened beverages, baked goods, desserts and sweets.
How to Read a Coffee Label
Total Sugars vs. Added Sugars. The FDA explains that Total Sugars include sugars naturally present in a food or drink plus any added sugars. Added Sugars are sugars added during processing, such as sucrose or dextrose. They don't include the naturally occurring sugars in milk, fruits and vegetables (FDA). A coffee drink made with milk can show Total Sugars even when its Added Sugars line reads zero.
Caffeine. The FDA says all packaged foods must list caffeine in the ingredient list when it is added as a stand-alone ingredient, while listing how much caffeine a product contains is voluntary (FDA). If a can doesn't state its caffeine, the label alone won't tell you.
The ingredient list. Sweeteners, syrups and creamers show up here even when the front of the package doesn't mention them. Reading it takes a few seconds.
FDA says up to 400mg a day is an amount not generally associated with negative effects for most healthy adults (FDA). The FDA also notes that certain conditions and some medications can make people more sensitive to caffeine's effects.
The Bottom Line
- Large observational studies associate regular coffee drinking with a lower rate of type 2 diabetes, in a dose-response pattern. That is an association, not proof of cause.
- In the short term, the AHA says caffeinated coffee may reduce insulin sensitivity.
- The AHA says sugar, syrups, milk and cream likely reduce whatever effects plain coffee may have.
- On a label, check Added Sugars, the ingredient list and whether caffeine is stated.
- If you're managing blood sugar, your doctor is the right person to ask about caffeine.
Frequently Asked Questions
Does coffee raise blood sugar?
The research separates two things. The AHA notes that caffeinated coffee may reduce insulin sensitivity in the short term, while long-term observational studies link regular coffee drinking with a lower rate of type 2 diabetes. Neither finding shows how coffee will affect any one person. If you're managing blood sugar, ask your doctor.
Is decaf different from regular coffee in these studies?
In the 2014 Diabetes Care meta-analysis, each additional daily cup was associated with about a 9% lower risk for caffeinated coffee and about 6% for decaf, and the difference between the two was not statistically significant.
Do sugar and cream matter?
The AHA says adding sugar, flavored syrups, milk or cream to coffee likely reduces whatever health effects plain coffee may have.
What's the difference between Total Sugars and Added Sugars?
According to the FDA, Total Sugars include naturally occurring sugars plus any added sugars. Added Sugars are only the sugars added during processing, such as sucrose or dextrose.
How much added sugar is the FDA's Daily Value?
50 grams per day, based on a 2,000 calorie diet.
Keep Reading
- Coffee, Caffeine and the Heart: What the AHA's 2026 Statement Says
- Cold Brew Coffee Ratio: The Water-to-Coffee Formula
- How Long to Steep Cold Brew: Time Chart and the Research
Sources:
- Ding M, Bhupathiraju SN, Chen M, van Dam RM, Hu FB. "Caffeinated and Decaffeinated Coffee Consumption and Risk of Type 2 Diabetes: A Systematic Review and a Dose-Response Meta-analysis." Diabetes Care, 2014;37(2):569-586.
- Bhupathiraju SN, Pan A, Manson JE, Willett WC, van Dam RM, Hu FB. "Changes in Coffee Intake and Subsequent Risk of Type 2 Diabetes: Three Large Cohorts of US Men and Women." Diabetologia, 2014;57(7):1346-1354.
- American Heart Association Professional. "Top Things to Know: Caffeine and Cardiovascular Disease," 2026.
- American Heart Association Newsroom, news release on its 2026 caffeine statement.
- U.S. Food and Drug Administration. "Added Sugars on the Nutrition Facts Label."
- U.S. Food and Drug Administration. "Spilling the Beans: How Much Caffeine Is Too Much?"
This article is general information, not medical advice. Bare Brew is a coffee drink, not a treatment for any condition. Each 12 fl oz can has 320mg of caffeine. It's not recommended for children, people who are pregnant or nursing, or anyone sensitive to caffeine. If you take medication or have a health condition, talk to your doctor about caffeine.
