Every summer, the same question resurfaces with the heat: how much water should a person actually be drinking, and is it possible to drink too much? KNSI put both questions to Dr. George Morris, sports medicine medical director at CentraCare in St. Cloud, Minnesota, and his answer cuts through a lot of the conventional wisdom that circulates every time the temperature climbs. Morris says there is no single number that fits everyone.
The familiar eight-glasses-a-day rule is not wrong, exactly, it is just incomplete. Morris says total fluid intake matters more than what comes specifically from a glass, and most people should aim for about two to two and a half liters of liquid a day, with a meaningful share of that coming from food rather than drinks.
Fruits, vegetables, and even protein sources like meat and beans carry water the body absorbs just as readily as a glass of water, and they bring along a bonus most people overlook: micronutrients and electrolytes that plain water simply does not contain.
That distinction matters because more water is not automatically better, and pushing past what the body actually needs carries its own risk. Morris pointed to what happens when someone drinks far beyond their needs. “If you drink in too much straight water, pure water, then you can dilute everything else and you end up with low electrolyte or low sodium levels, which is risky,” he said.
Read more: Mozambique advocates for sustainable land and water management in Africa
That condition has a clinical name, hyponatremia, and it’s the reason Morris specifically warns against chugging large amounts of water before a workout or before heading out for a long day in the heat.
He also took aim at one of the more persistent formulas that circulates in fitness and weight-loss circles, the idea that a person should drink one ounce of water for every two pounds of body weight. For someone who weighs 180 pounds, that works out to 90 ounces a day, and Morris says that’s likely more than necessary on a routine basis. The formula treats hydration as a fixed ratio when, in his view, it should track activity level, climate, and individual physiology instead.
Plain water remains a perfectly good default for everyday sipping, but Morris says the calculation changes once real exertion or heat exposure enters the picture.
“Especially if you’re exercising or sweating heavily out in the sun on a long day, on a picnic or a boat ride, or even at a local parade, having some electrolytes in your water is a great idea,” he said.
Read more: Mozambique: UK has invested €68.9 million in water supply
The medical expert noted that the World Health Organization publishes a do-it-yourself oral rehydration recipe using a small amount of salt, sugar, and baking soda, though Morris says a commercially available electrolyte mix accomplishes the same thing just as effectively for most people. For longer physical efforts, a bike ride, a run, or a softball tournament, his rule of thumb is to add about a cup of water for every 45 minutes of activity.
For anyone unsure whether they’re drinking enough on a given day, Morris offered a simple, free, at-home check that doesn’t require tracking ounces or liters at all. “You want your urine to be really very light yellow or even clear,” he said.
“That means you’re getting enough water and your body is filtering it quite effectively.” Dark or concentrated urine, on the other hand, is a clear and immediate signal that more fluid is needed.
A handful of groups warrant closer attention than the general population. Young children, older adults, and pregnant women should all pay more deliberate attention to their hydration levels, with the elderly facing a higher risk on two fronts at once, both low sodium levels and added strain on the heart from overhydration.
Read more: Hundreds of thousands in Ukraine left without power, heat and water after Russian attacks
For everyone else, Morris’s underlying advice resists the urge to overcomplicate the question. Drink steadily through the day rather than in large bursts, favor water and whole food over sugary or caffeinated alternatives, and treat the body’s own signals, urine color chief among them, as a more reliable guide than any single rule of thumb floating around the internet
