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Is it possible to drink too much water?
I typically drink far more than the recommended six to eight glasses per day, and feel dehydrated if I adhere to the guidelines. I have no underlying medical conditions, such as diabetes, that would lead to increased thirst.
Reader Question • 465 votes

Absolutely, and if you do, you can develop a dangerous condition called hyponatremia, or water intoxication.

Under normal conditions, the body beautifully maintains its fluid balance. Lose fluids through sweating, for instance, and your body responds with the feeling of thirst. You drink. If you swallow more liquid than needed just then, your body typically responds by excreting the excess through urination.

But should you consume so much fluid that your body can’t easily rid itself of the surplus, you dilute sodium levels in your blood. Osmosis then draws water from the blood into body cells to equalize sodium levels, and those cells swell. At that point, you have hyponatremia. If the cellular bloating occurs in the brain, it can be fatal.

Until about 20 years ago, hyponatremia was extremely uncommon among healthy people. But then several marathon runners died from hyponatremia. In general, they had been middle- or back-of-the-pack, slower runners. They did not sweat much. But they drank plenty of water, trying to ensure that they would be well hydrated.

Today, most knowledgeable coaches and exercise experts warn athletes not to overdrink. “You should drink only when you need to, when you are actually thirsty,” said Dr. James Winger, a professor of family medicine at Loyola University Medical Center, who has studied the hydration habits of athletes.

If you’re not sure whether you’re drinking too much or too little during exercise, try weighing yourself before and after a lengthy workout, experts advise. If you have lost more than about 3 or 4 percent of your body weight, you’re probably flirting with dehydration and might want to drink a bit more next time. But if you have gained weight or your fingers seem swollen and your rings tight, you’re most likely drinking too much and should moderate intake.

Most important, listen to your body’s signals, Dr. Winger said. “Thirst is a very reliable indicator,” he said, of whether and how much to drink.