You’re likely aware that sweating is how your body cools off, and that when you sweat, your body loses water, salt, and other minerals. What you might not know, though, is just how much you need to drink to replenish these fluid losses.
People often don’t “drink as much fluid as they’re really supposed to,” says Dr. Cara Taubman, clinical director of emergency management at NYC Health + Hospitals in Harlem. “You really need to drink more fluids than you realize.”
That’s true whether you’re sitting inside in the air conditioning, exercising, going to the pool, or working outside in the summer heat, Taubman says.
Thirst is your body’s “strong inherent mechanism” to signal when you need to hydrate, explains Dr. Rakhi Khanna, a nephrologist at Rush University Medical Center in Chicago. But you shouldn’t always wait until you’re thirsty—you also need to consume fluids throughout the day, including with meals.
Here’s the best thing to drink to stay hydrated and how much you need.
What’s the best drink for hydration?
“Water is by far the best fluid to drink,” says Craig Crandall, professor of internal medicine at the University of Texas Southwestern Medical Center in Dallas. “You’re losing water, and you need to replace the water.”
The National Academies of Sciences, Engineering and Medicine says women generally need about 2.7 liters (11.4 cups) of water a day, and men need 3.7 liters, or 15.6 cups.
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But these quantities are a baseline, Taubman says. This is likely enough water if you’re staying inside for most of the day, but several factors influence how much you actually need to drink.
For instance, Khanna says, “If you are working outside in the heat, you may need to drink extra.” The same goes for anyone who sweats a lot, such as from exercising, Crandall says. “It all comes down to how much water you’re losing when you sweat.”
When do you need electrolytes?
On an especially hot day when you’re extra sweaty, you may think a sports drink containing electrolytes—sodium and other minerals that your body needs—is a better option than water. And sometimes it is, Crandall says.
Your sweat contains water and electrolytes. “That’s why your sweat will taste salty,” he explains. “You’re losing salt and water. If you just replace water, everything’s OK for the first hour or so.”
In other words, drinking water alone will suffice when you’re sweating for short periods of time (about an hour), but if you’re continuing to sweat longer than that—for example, you work in construction and spend most of your day outside, an electrolyte drink is beneficial, Crandall says.
“You need to replace that salt,” he emphasizes. If you don’t, you could dilute the amount of salt in your blood, which may lead to hyponatremia, a serious condition causing cognitive problems, nausea, and muscle weakness.
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However, if you spend most of your day indoors not sweating, you usually don’t need sports drinks, Taubman says, as you’re probably getting enough electrolytes from food.
It’s also “important to drink something with electrolytes if you’re having nausea, vomiting or diarrhea, or not eating,” Khanna adds. That’s why electrolyte drinks are often recommended when you have a stomach bug.
If you are buying a sports drink or electrolyte powder, Taubman suggests avoiding products with excessive added sugar. “Higher amounts of sugar can actually lead to dehydration in the long run,” she says.
Some foods can keep you hydrated
Foods with a higher water content are helpful for overall hydration, Khanna says. Cucumber, watermelon, lettuce, tomatoes, and strawberries are a few fruits and vegetables in this category.
“We get about 20% of our fluid intake through foods, and a lot of these water-dense foods are actually a really good way to increase your fluid intake in general,” Taubman says.
These foods contain some electrolytes, too, she adds. You can also add them to plain water to add a little flavor.
Drinks to avoid for hydration
Alcohol, sugary beverages, and caffeine can be dehydrating, according to the Cleveland Clinic. Drinking a glass of water for every alcoholic beverage can help you avoid dehydration in some instances, however.
Caffeine is a diuretic, which means it can make you pee and possibly raise your risk for dehydration, Taubman says. But coffee and tea aren’t always a no-no for hydration. “You can eliminate some thirst by drinking coffee, but it’s not the ideal drink,” Khanna says.
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Still, iced coffee or tea could increase the volume of fluids you’re drinking, Taubman says. “I live on iced coffee during the summer. If that makes you drink more fluids, you’re making it up with the volume, especially if you’re not putting a ton of sugar in it.”
Signs that you’re not drinking enough fluids
If you’re generally healthy, the easiest way to gauge your hydration level is to look at your urine, Taubman says. You should be peeing regularly, and if you’re not, that’s a sign you need more fluids. Also, your urine should be a pale yellow color; if it’s darker, she says you need more water.
Dizziness, fatigue, headaches, nausea, muscle cramps, confusion, and irritability are signs of dehydration, Taubman says. If you’re having them, Crandall says to stop what you’re doing, head into the air conditioning, and hydrate yourself. Seek medical attention if you don’t feel better within a few minutes.
“The problem with dehydration is it’s very vague until it isn’t,” Taubman says. “When it’s really hot, it’s something we should be mindful of, because you may not see things until it’s too late.”
