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Published on August 17, 2015

Is too much water a bad thing?Is too much water a bad thing?

When exercising in warm weather, many people worry about dehydration, and they should. But overhydrating can be even more dangerous and can lead to a condition called exercise-associated hyponatremia, EAH.

“It’s very serious,” says Melanie Greenan, M.D., a kidney specialist for Cape Cod Hospital. “It can lead to seizures and death. But thankfully, it is not that common.”

Over-hydration occurs when a person’s body takes in too much water and the salt level in the blood falls too low. A lot of athletes think that drinking electrolyte enhanced drinks like Gatorade or Pedialyte will prevent EAH, but Dr. Greenan says those drinks aren’t significantly better than drinking plain water.

Symptoms of over-hydration occur quickly and include headaches, nausea and confusion.

“If an athlete appears confused, that’s definitely a reason to seek medical attention,” Dr. Greenan says.

In the past, over-hydration was mostly associated with athletes who participate in events like marathon or triathlons. That is no longer true.

In July, international EAH experts gathered in California for their third annual conference identified the condition in a wider range of sporting activities. They have documented at least 14 deaths since 1981, including two high school football players who died from over-hydration in 2014.

Both Zyrees Oliver, a 17-year-old in Georgia and Walker Wilbanks, a 17-year-old from Mississippi died after drinking too many fluids while playing football in August 2014.

The increase in deaths has led the international group to create new guidelines published in the Clinical Journal of Sport Medicine.

One of their biggest recommendations is to let your thirst be your guide, but Dr. Greenan says that is not always a good idea.

“That can actually be kind of tricky because sometimes thirst lags,” she says. “I run myself and I have finished runs not feeling very thirsty and then realized later in the day that I’m dehydrated.”

Different bodies have different fluid needs based on the amount you sweat and other factors, she says. Rather than automatically pushing fluids, she recommends practicing with hydration as you exercise to see what ratio makes you feel the best.

Another tip: Weigh yourself before a workout, don’t drink anything during the workout and then weigh yourself afterwards. Any weight loss is pure water.

It’s normal to lose a pound or two during normal exercise, so that can be your individual guide. If you lose more, you need extra hydration.

“It’s the kidneys’ job to get rid of any extra water you take in,” Dr. Greenan says. “It actually takes a lot to overwhelm the kidney system, so people would have to drink a lot of water in a short period of time to run into trouble. For most of us, the kidneys will get rid of the extra water with no problem.”