Is watermelon good for diabetics?
Watermelon is a low-glycemic food: its glycemic index is 50 (median of 4 lab tests, range 47 to 55). A serving of 1 cup, balls (5.4 oz, 154 g) has 11.6 g of carbs and 0.6 g of fiber, a glycemic load of about 6.
This page is for people with diabetes or prediabetes. The glycemic index compares foods, and the glycemic load on this page adjusts it for a real serving. If you follow a meal plan from your care team, use these numbers within it.
Carbs in a serving
| Per 1 cup, balls (5.4 oz, 154 g) | Amount |
|---|---|
| Total carbohydrate | 11.6 g |
| Fiber | 0.6 g |
| Sugars | 9.5 g |
| Carbs minus fiber | 11 g |
| Glycemic load (GI × carbs minus fiber ÷ 100) | 6 |
USDA FoodData Central, Watermelon, raw. Glycemic load uses the median GI below.
Glycemic index tests
| Food as tested | GI | Category | Country |
|---|---|---|---|
| Watermelon (Citrullus lanatus), raw, yellow-fleshed, seedless | 47 | low | Malaysia |
| Watermelon (Citrullus lanatus), raw, red-fleshed, seeded | 48 | low | Malaysia |
| Watermelon (Citrullus lanatus), raw, red-fleshed, seedless | 51 | low | Malaysia |
| Watermelon, raw (Citrullus vulgaris-red variety) | 55 | low | Malaysia |
Glucose = 100. Categories from the International Tables: low 55 or less, medium 56 to 69, high 70 or more. Only tests that met the ISO 26642:2010 method (Supplemental Table 1).
Compared with similar foods
| Food | Portion | GI | Carbs | Glycemic load |
|---|---|---|---|---|
| Watermelon | 1 cup, balls (5.4 oz, 154 g) | 50 | 11.6 g | 6 |
| Apple | 1 cup, quartered or chopped (4.4 oz, 125 g) | 44 | 17.3 g | 6 |
| Banana | 1 banana, peeled (4.1 oz, 115 g) | 52 | 26.4 g | 13 |
| Grapes | 1 cup (5.3 oz, 151 g) | 54 | 27.3 g | 14 |
Same food group in the International Tables, each at its usual US portion (USDA).
How much the glycemic index matters
Studies and guidelines do not agree on how much weight to give the glycemic index.
- Level C A year after the World Health Organization set the glycemic index aside, a meta-analysis of cohorts each over a hundred thousand people linked high glycemic index diets to more diabetes, heart disease and death. Lancet Diabetes & Endocrinology, 2024
- Level E The World Health Organization examined the glycemic index, found it inconsistent, and refused to build guidance on it. Carbohydrate intake for adults and children: WHO guideline, 2023
- Level C Glycemic index and glycemic load, the other two ways of judging carbohydrate, held up far worse than fiber in the same analysis. Reynolds et al., The Lancet, 2019
What studies found about watermelon
- Level A The same 2023 meta-analysis of 9 randomized trials found that watermelon consumption significantly raised fasting blood sugar. Diabetes Res Clin Pract, 2023
- Level B In a glycemic index test in 10 healthy adults, Malaysian watermelon had a GI of 55, in the low range. Asia Pac J Clin Nutr, 2008
- Level C A meta-analysis of 5 cohort studies found eating more fruit during pregnancy was not linked to gestational diabetes. Complement Ther Med, 2020
Levels: A is a meta-analysis of trials, B a randomized trial, C an observational study, D lab or animal work, E an expert position. How we grade evidence.
In practice
All four tests that met the ISO method landed between 47 and 55, which is the low band. Watermelon is mostly water, so a cup has only 11.6 g of carbs and a glycemic load of about 6.
The catch is the portion. A cup is easy to pass when you eat it by the wedge, and every extra cup adds another 11.6 g of carbs, nearly all of it sugar (9.5 g a cup).
A low GI is not the whole story. A 2023 pooled analysis of 9 randomized trials of watermelon found it raised fasting blood sugar. If you track your readings, a cup at a time makes it easier to see how it works for you.
Evidence behind this note
- Level A The same 2023 meta-analysis of 9 randomized trials found that watermelon consumption significantly raised fasting blood sugar. Diabetes Res Clin Pract, 2023
- Level B In a glycemic index test in 10 healthy adults, Malaysian watermelon had a GI of 55, in the low range. Asia Pac J Clin Nutr, 2008
Written from the agency positions and data on this page, reviewed by the Bioma editorial system. How we verify.
Keep exploring
Sources
- Atkinson FS et al. International tables of glycemic index and glycemic load values 2021: a systematic review. Am J Clin Nutr 2021;114(5):1625-1632, Supplemental Table 1, PMID 34258626, doi:10.1093/ajcn/nqab233 (accessed 2026-10-12)
- USDA FoodData Central, SR Legacy (2018): Watermelon, raw, FDC ID 167765
- USDA FoodData Central, SR Legacy (2018): Apples, raw, with skin (Includes foods for USDA's Food Distribution Program), FDC ID 171688
- USDA FoodData Central, Foundation Foods (release 2025-12-18): Bananas, ripe and slightly ripe, raw, FDC ID 1105314
- USDA FoodData Central, SR Legacy (2018): Grapes, red or green (European type, such as Thompson seedless), raw, FDC ID 174683
- Evidence cards: each study above links to its source. Card review dates are listed in our methodology.
Sources checked 2026-10-12. Bioma Learn provides information, not medical advice.