Diabetes Forecast

How much should I drink to stay hydrated while I exercise? Are electrolytes necessary?


Carla Cox, PhD, RD, CDE, CSSD, FAADE, responds

It’s important to drink enough fluids before, during, and after your workout, particularly in the summer, when temperatures climb.

What to Know

People with diabetes have the same risk for dehydration during exercise as everyone else—except when blood glucose levels are elevated. As glucose in the blood rises, more fluid is sent into the bloodstream to dilute the glucose. This leads to frequent urination in larger amounts, which lowers the body’s total fluid.

How much you need to drink to stay hydrated depends on a number of factors, including your weight, fitness level, the air temperature, time spent exercising, and whether you’re exercising indoors or outside. 

Find Out More

It’s important to be well hydrated before you begin any physical activity. That means drinking fluids one to two hours before you start. For workouts that will last an hour or less, aim for 3 to 8 fluid ounces of water every 15 to 20 minutes.

If you’re engaging in intense activity for more than an hour or in very hot weather, you’ll need to hydrate and keep your blood glucose from going too low. Sports drinks with glucose and electrolytes (minerals that help the body maintain normal fluid levels) are a good choice. They can also help you replenish sodium, an electrolyte that helps hold fluid in the bloodstream, which you lose while sweating. Stay hydrated by drinking 4 to 8 ounces of sports drink every 15 to 20 minutes. (Each 8-ounce cup should have an average of 15 grams of carbohydrate. The general recommendation for blood glucose management during intense exercise is to eat or drink up to 60 grams of carbohydrate per hour. Adjust this amount depending on your personal needs.) If you prefer water, get glucose and electrolytes through sports gels.

Not sure whether you’re drinking enough? Check the color of your urine: If it’s pale yellow, you’re well hydrated. Dark urine indicates your body needs fluid. 

Be alert for signs of dehydration. They include dry mouth, excessive thirst, light-headedness, and headache. Symptoms of dehydration may be mistaken for low or high blood glucose—and vice versa. While working out, check your blood glucose as directed for the type of medication you take. Your doctor may ask you to check before, during, and after exercise.

Before you begin your exercise routine, weigh yourself. When you’re finished, drink three cups of fluid for every pound of weight lost due to sweating in order to replenish what you lost during your activity. Alternatively, drink enough until your thirst is satisfied. 


Maintain your blood glucose targets in the hours leading up to exercise, consume fluids about one to two hours prior to exercise, and be sure to drink while you’re working out. Learn the symptoms of dehydration and treat immediately to avoid further dehydration. Don’t forget to rehydrate after your workout.

Carla Cox, PhD, RD, CDE, CSSD, FAADE, is a diabetes educator and has worked with people with diabetes for over 30 years.

Read more from our Active Lifestyle Guide.



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