Watermelon glycemic index and glycemic load
Watermelon has a low glycemic index of 50 (the median of 4 lab tests, range 47 to 55) in the 2021 International Tables, where pure glucose is 100. A serving of 1 cup, balls (5.4 oz, 154 g) has 11 g of carbs minus fiber, which gives a glycemic load of about 6.
Glycemic load by portion
| Portion | Carbs | Fiber | Carbs minus fiber | Glycemic load |
|---|---|---|---|---|
| 1 cup, balls (5.4 oz, 154 g) | 11.6 g | 0.6 g | 11 g | 6 |
| 1 cup, diced (5.4 oz, 152 g) | 11.5 g | 0.6 g | 10.9 g | 5 |
| 1 wedge (10.1 oz, 286 g) | 21.6 g | 1.1 g | 20.4 g | 10 |
| 10 watermelon balls (4.3 oz, 122 g) | 9.2 g | 0.5 g | 8.7 g | 4 |
Glycemic load = GI 50 × carbs minus fiber ÷ 100. Carbs from USDA FoodData Central, Watermelon, raw.
Every standardized test
| Food as tested | GI | Category | Country |
|---|---|---|---|
| Watermelon (Citrullus lanatus), raw, yellow-fleshed | 47 | low | Malaysia |
| Watermelon (Citrullus lanatus), raw, red-fleshed | 48 | low | Malaysia |
| Watermelon (Citrullus lanatus), raw, red-fleshed | 51 | low | Malaysia |
| Watermelon, raw (Citrullus vulgaris-red variety) | 55 | low | Malaysia |
The tables' own average for this food: 50 (mean of four foods).
Glucose = 100. Low 55 or less, medium 56 to 69, high 70 or more (category cut-offs from the International Tables). Only tests that followed the ISO 26642:2010 method: at least 10 healthy adults, a portion with 25 or 50 g of available carbs (Supplemental Table 1).
Compared with similar foods
| Food | GI | Portion | Carbs minus fiber | Glycemic load |
|---|---|---|---|---|
| Strawberries | 40 | 1 cup, halves (5.4 oz, 152 g) | 8.6 g | 3 |
| Apple | 44 | 1 cup, quartered or chopped (4.4 oz, 125 g) | 14.3 g | 6 |
| Orange | 45 | 1 cup sections no membranes (5.8 oz, 165 g) | 16.2 g | 7 |
| Banana | 49 | 1 banana, peeled (4.1 oz, 115 g) | 24.5 g | 12 |
| Watermelon | 50 | 1 cup, balls (5.4 oz, 154 g) | 11 g | 6 |
Same group in the International Tables (Fruit), each at its usual US portion. A low GI with a big portion can give a higher glycemic load than a high GI with a small one.
Older and smaller studies
3 more tests of watermelon are listed in the tables' second list (50 to 80, median 72). They deviate from the ISO method: fewer than 10 people, people with diabetes, a different reference food or sampling time, or wide variation. They are not part of the number at the top.
Show the 3 tests
| Food as tested | GI | Country | Who was tested |
|---|---|---|---|
| Watermelon (Citrullus vulgaris), raw | 50 | Jamaica | healthy, 10 people |
| Watermelon, raw | 72 | Australia | healthy, 8 people |
| Watermelon, raw | 80 | Australia | healthy, 8 people |
Supplemental Table 2 of the International Tables. NS means the study did not specify.
How much the glycemic index tells you
Researchers and health bodies do not agree on how much weight to give the glycemic index of single foods.
- 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 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 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 and blood sugar
- Level A Watermelon lowered blood pressure and cholesterol in pooled trials, and raised fasting blood sugar. Diabetes Res Clin Pract, 2023
- Level B In 10 healthy volunteers, watermelon had a glycemic index of 55, classed as low, against 82 for pineapple. Asia Pac J Clin Nutr, 2008
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.
Keep exploring
Sources
- Atkinson FS, Brand-Miller JC, Foster-Powell K, Buyken AE, Goletzke J. 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 and Supplemental Table 2, 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): Strawberries, raw, FDC ID 167762
- 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): Oranges, raw, navels, FDC ID 746771
- USDA FoodData Central, Foundation Foods (release 2025-12-18): Bananas, ripe and slightly ripe, raw, FDC ID 1105314
- 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.