Bananas and Diabetes: Carbs, Glycemic Index and Portions
A medium banana has about 27 g of carbohydrate (24 g net). Glycemic index: low to medium (47 to 57). Yes, in sensible portions. A banana is a fruit that fits into a carbohydrate-aware plan; the size and ripeness are what change the numbers.
Bananas are one of the first fruits people ask about, mostly because they are sweet and easy to overeat. The good news is that a banana comes with its own portion control: one medium fruit is a measured serving of carbohydrate you can count and plan around.
Ripeness matters. As a banana turns from green to spotted, more of its starch becomes sugar, so a very ripe one tends to raise glucose a little faster than a firm, just-yellow one. If bananas are a favorite, try a smaller one, or half now and half later.
Carbs in bananas by portion
| Portion | Grams | Carbs (g) | Fiber (g) | Net carbs (g) | Protein (g) |
|---|---|---|---|---|---|
| 1 medium | 118 | 27 | 3.1 | 24 | 1.3 |
| 1 cup, sliced | 150 | 34 | 3.9 | 30 | 1.7 |
| 100 g (for comparing foods) | 100 | 23 | 2.6 | 20 | 1.1 |
Source: USDA FoodData Central, FDC ID 173944 (Banana). 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
GI ranks how fast a food raises blood glucose compared with pure glucose (100). Low is 55 or less, medium 56 to 69, high 70 or more. Studies of ripe and unripe bananas give different values, which is why the table shows a range. Glycemic load multiplies the index by the available carbohydrate in a portion (carbs minus fiber), so it reflects how much you actually eat: low is 10 or less, medium 11 to 19, high 20 or more.
Which published values we used (4)
| Entry | Food as listed | GI |
|---|---|---|
| Suppl. Table 1, #1088 | Banana, raw | 47 |
| Suppl. Table 1, #1089 | Banana, lady finger (Moraitis, Australia) | 49 |
| Suppl. Table 1, #1090 | Banana, lady finger (Moraitis, Australia) | 53 |
| Suppl. Table 1, #1091 | Banana, raw, overripe | 57 |
Atkinson FS et al. International tables of glycemic index and glycemic load values 2021. Am J Clin Nutr 2021;114(5):1625-1632. Glucose reference (glucose = 100); values from studies that used white bread were converted by the authors. Where studies differ we show the range, not an average.
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 bananas fit the plate method
Bananas count toward the carbohydrate quarter of the plate in the plate method, along with grains, starchy vegetables, fruit and milk. 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 bananas onto a meal in the meal planner to watch the plate fill.
Portion ideas and pairings
- Half a banana is an easy snack portion.
- Slice it over oatmeal or plain yogurt instead of eating it alone.
- A “large” banana can carry noticeably more carbohydrate than a small one, so size is worth checking.
Pairs well with: peanut butter or a handful of nuts, plain yogurt, cottage cheese.
Related foods
Apple
cup, quartered or chopped: 17 g carbs
Strawberries
cup, halves: 12 g carbs
Watermelon
cup, balls: 12 g carbs
Grapes
cup: 27 g carbs
See all foods and the low glycemic foods list
Frequently asked questions
Is a banana a good snack for someone with diabetes?
It can be. A smaller banana with a protein or fat, such as nut butter, is a common pairing. How it affects you is individual, so check with your meter or CGM and talk with your care team.
How many carbs are in a medium banana?
About 27 g of carbohydrate, of which about 3.1 g is fiber, so roughly 24 g net carbs. Values are from USDA FoodData Central for 118 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: Banana (FDC ID 173944)
- 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.
