Coffee and Diabetes: Carbs, Glycemic Index and Portions
A cup of black coffee has about 0 g of carbohydrate (0 g net). Glycemic index: not applicable. Yes. Plain black coffee has no carbohydrate, so what you add is what counts.
Black coffee has essentially no carbohydrate. The sugar, syrups, flavored creamers and milk are where carbohydrate sneaks in, and a large flavored latte can have as much as a dessert.
Caffeine affects some people’s glucose and not others, so if you notice a pattern, your meter or CGM will show it.
Carbs in coffee by portion
| Portion | Grams | Carbs (g) | Fiber (g) | Net carbs (g) | Protein (g) |
|---|---|---|---|---|---|
| cup | 237 | 0 | 0 | 0 | 0.2 |
| 100 g (for comparing foods) | 100 | 0 | 0 | 0 | 0.1 |
Source: USDA FoodData Central, FDC ID 171890 (Coffee, black). Net carbs here means carbohydrate minus fiber. “Net carbs” is not an FDA-defined term, so total carbs are shown too. Values are estimates for a typical item; brands, ripeness and size vary.
Glycemic index and glycemic load
Glycemic index: not applicable. Almost no carbohydrate, so a glycemic index does not apply.
Glycemic index is only one piece of the picture. The same food can give a different response depending on ripeness, cooking, what you eat it with and your own body, so your meter or CGM is the best guide.
How coffee fit the plate method
Coffee are a drink, not a plate section, so the plate method does not place them. What matters is what is in the cup or glass. The CDC describes the plate method as half non-starchy vegetables, a quarter protein and a quarter carbohydrate foods. See the diabetic meal plan guide for how it works, or drop coffee onto a meal in the meal planner to watch the plate fill.
Portion ideas and pairings
- Black or with a splash of milk.
- Use cinnamon or unsweetened flavoring.
- Ask for a small size and half the syrup.
Pairs well with: a protein-rich breakfast, water throughout the day.
Related foods
Beer, regular
can: 12 g carbs
Red wine
serving: 3.8 g carbs
Diet soda
can: 0.4 g carbs
Banana
1 medium: 27 g carbs
See all foods and the low glycemic foods list
Frequently asked questions
Does coffee raise blood sugar?
Black coffee does not contain carbohydrate. Some people’s glucose rises a bit with caffeine. Watch your own readings.
How many carbs are in a cup of black coffee?
About 0 g of carbohydrate, of which about 0 g is fiber, so roughly 0 g net carbs. Values are from USDA FoodData Central for 237 g and are estimates; brands and sizes vary.
Information only, not medical advice. Your care team may set different targets for you, and only a lab test ordered by a clinician can diagnose diabetes or prediabetes. See our medical disclaimer.
Sources
- USDA FoodData Central: Coffee, black (FDC ID 171890)
- Atkinson FS et al. International tables of glycemic index and glycemic load values 2021. Am J Clin Nutr 2021;114(5):1625-1632
- CDC: Diabetes Meal Planning (plate method and carbohydrate counting)
- ADA Standards of Care in Diabetes—2026, Section 5: Facilitating Positive Health Behaviors
Last reviewed: by the Diabetes Blogs editorial team. Information only, not medical advice.
