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  • Sheri Colberg, PhD

Stay Hydrated Without Overhydrating for Exercise

Updated: Jun 23, 2021

Hydrate with water and fruit

Adequate fluid intake is essential to living well at any age, and being dehydrated can impact your health and your athletic endeavors. While it is harder to stay hydrated when exercising in the heat, you can dehydrate under other conditions—even during exercise in cold temperatures if you wear lots of clothing and sweat underneath it. As people grow older, they also begin to lose some of their normal thirst sensations, thereby increasing the risk for dehydration unless they make a conscious effort to drink more.

Diabetes adds its own dehydration concerns. Elevated blood glucose levels (typically when above ~200 mg/dL) lead to glucose loss through urine, which takes extra water with it and can cause dehydration. In addition, taking some of the newer medications like SGLT2-inhibitors that increase urine output whenever blood glucose rises above that level may also lead to excess water losses. If exercising when your blood glucose is higher or after it has been elevated, take care to drink enough fluids to rehydrate. If you are older or have been diagnosed with autonomic neuropathy (central nerve damage), take extra care as your body’s ability to regulate your body temperature through sweating may be impaired as well.

Hydration Tips for Exercise

  • Drink cool water or other fluids before, during, and after you are physically active, especially during warmer or more humid conditions.

  • If you prefer fluids with some flavor, try flavored waters, sports drinks that have no added carbohydrates or calories, and add a pinch of salt if you want it to taste and be more like a sports drink.

  • Only drink regular sports drinks (containing glucose) when you need some carbohydrate to prevent or treat hypoglycemia during activities.

  • Drink only when you feel thirsty and only enough to satisfy your thirst to avoid water intoxication.

Whether you should drink water, sports drinks, or other fluids during exercise when you have diabetes depends on your blood glucose levels. For shorter activities (lasting an hour or less), plain water should suffice for hydration. If you need some carbohydrate, you can supplement and hydrate by using a sports drink like Gatorade or PowerAde or diluted fruit juice. Normally you do not need to replace electrolytes, like sodium, potassium, and chloride, unless you are exercising outdoors in hot weather for more than two hours at a time. Even then, in most cases you can wait to replace electrolytes naturally with your food the next time you eat.

You can also harm yourself by drinking too much fluid at any time, but especially during exercise. If you drink too much (leading to clear urine), you increase your risk of diluting the sodium content of your blood, potentially causing hyponatremia, or water intoxication, and raising the risk of seizures, coma, and even death. To avoid overhydrating, only start drinking when you feel thirsty during exercise. If you have hyperglycemia or autonomic neuropathy, start drinking small amounts of water as soon as you start sweating.

During physical activity, you will be sweating and losing water in other ways (like through breathing), so your body weight should decrease until you have a chance to rehydrate. After exercise, you can rehydrate with water or other non-caloric fluids but replace only the weight you lost. If you already took in a lot of fluid during an activity, wait until you start to urinate before drinking any more.

To hydrate effectively after exercise, consider taking in fluids containing protein and fat that may rehydrate you more effectively than plain water. Eating a piece of fruit (or likely anything) when drinking plain water may also promote more effective rehydration. What’s more, drinking small amounts more frequently instead of large volumes at one time (that is, a slow and steady approach to hydrating) helps you better retain the fluid that your body needs.

Luckily for all the coffee drinkers, caffeinated drinks usually hydrate you as well as caffeine-free ones if they contain enough fluids (so avoid espresso). Taking in too much caffeine can cause your bones to lose calcium, so the decaf options may be better ones. Dehydration also contributes to constipation and taking in enough fluids can help you stay regular.

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