Kidney Diet Tips

Is watermelon safe for a kidney diet?

This week a question came up about watermelon in the dialysis diet. Some patients are told to avoid watermelon while others are told it’s ok to include. Why the mixed messages? It has to do with 3 issues—portion size, potassium and fluid.

  • Portion: The typical portion is a wedge of watermelon—equal to about 3 cups. For a dialysis diet that includes limited potassium and fluid, a wedge of watermelon contributes too much potassium and fluid. Most dietitians advise limiting watermelon to a 1 cup serving. Instead of cutting a wedge, cut the watermelon into bite-size pieces and measure into a cup.
  • Potassium: Knowing how many fruits and vegetables to eat and the best portion size is essential to controlling potassium intake. A wedge of watermelon contributes 560 mg potassium but a smaller 1 cup serving contains only 180 mg potassium. Since a one cup portion of watermelon is smaller than a typical portion, try measuring your servings until you can successfully guesstimate a 1 cup portion. You can also cut your portion into small triangular pieces as sometime seen when watermelon is placed on a salad bar or used as a garnish. Most other melons are much higher in potassium compared to watermelon. For this reason watermelon is usually the only melon included in a low potassium diet plan.
  • Fluid: It’s easy to exceed your fluid goals if you don’t count watermelon as part of your fluid intake. That’s because watermelon is 92% fluid and has little fiber. A wedge of watermelon has close to 3 cups of fluid!  For dialysis patients on a fluid restriction, watermelon is limited to 1 cup and may be counted as a replacement for fluid if water weight gains are a concern.

Nutritionally, watermelon is a good source of vitamin C, beta carotene and lycopene, a phytochemical with antioxidant activity that may protect against cancer. As mentioned, when consumed in small portions it is also low in potassium, and naturally very low in phosphorus and sodium.

Once available only during summer months, watermelon is now available year round in most large markets. Consider adding watermelon to your favorite fresh fruit salad. Make summer salsa with watermelon as a replacement for tomato. For a special refreshing watermelon treat, try Watermelon Cooler from the kidney-diet recipe collection.


Kidney diet resources from

Sara Colman, RD, CDE

Sara is a renal dietitian with over 20 years experience working with people with diabetes and kidney disease. She is co-author of the popular kidney cookbook "Cooking for David: A Culinary Dialysis Cookbook". Sara is currently the Manager of Kidney Care Nutrition for DaVita. She analyzes recipes and creates content, resources and tools for the kidney community. In her spare time Sara loves to spend time with her young grandson, including fun times together in her kitchen.