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Hyponatremia: the danger of drinking too much water

Hyponatremia-the-danger-of-drinking-too-much-waterDehydration is one of the biggest threats facing athletes. But endurance athletes are also at risk for drinking too much water.

Hyponatremia basics

Hyponatremia is a life-threatening condition that happens when there is a dangerously low level of sodium in the blood. Sodium is an electrolyte that helps regulate the amount of water in and around your cells. In hyponatremia, the body’s water levels increase too much and the cells swell. This can lead to dangerous health complications, such as brain swelling, coma, and even death.

Hyponatremia can be caused by an underlying medical problem, but in endurance athletes it occurs as a result of drinking too much water. Hyponatremia is more likely to happen during long endurance events, like marathons, ultras, 100-mile bike races, and long triathlons. Casual runners who only run a few miles at a time do not have to worry about hyponatremia.


Signs of hyponatremia include the following:

  • Nausea and/or vomiting
  • Extreme fatigue and loss of energy
  • Confusion
  • Restlessness and irritability
  • Muscle cramps or spasms
  • Seizures
  • Loss of consciousness

Note these symptoms aren’t specific to hyponatremia -– muscle cramps and headaches are also signs of dehydration, for example. But it’s better to be safe than sorry. Stop running and seek medical help at once if you have any signs of hyponatremia during a long run or race.

Treatment for hyponatremia includes taking a sodium solution intravenously (through an IV) to regulate the body’s fluid levels.

Prevent hyponatremia

Taking these actions can lower your risk of hyponatremia:

  • Rehydrate with sports drinks. There’s a reason why most races offer sports drinks along the course. These beverages contain sodium and other vital electrolytes. Drinking them before, during, and after long or intense runs can help keep your electrolyte levels balanced.
  • Drink the right amount of water throughout the day and during races. To learn more about your fluid needs, check out this article.
  • Be extra careful when running in hot weather. Exercising in hot or humid conditions causes you to lose more sodium through sweat. Keep summer runs short and rehydrate with sports drinks.
  • Weigh yourself before and after exercise. If you weigh more after a run than before it, the weight you gained was likely due to drinking too much water. Play around with your fluid intake during runs. Once the scale doesn’t move much — in either direction — you’ve likely found your hydration sweet spot.
  • Watch your overall salt intake. Most Americans consume too much salt — most processed foods and restaurant meals are loaded with sodium. If you eat pretty healthy, though, there’s a chance you may not be getting enough salt. Eat broth-based soups and snack on pretzels, nuts, and whole grain tortilla chips to up your salt intake. (Or make some pickle juice ice pops.)

Some athletes take salt tablets during marathons in hopes of preventing hyponatremia. But experts disagree on whether this is helpful or not. Hyponatremia doesn’t stem from taking in too little salt. Rather its caused by drinking too much water, so taking in extra salt won’t necessarily prevent hyponatremia. It’s a better idea to curb your water intake than to rely on salt tablets.

While hyponatremia is a risk for endurance athletes, keep in mind dehydration is much more common. In fact, notes from the Boston Marathon’s medical team show that six times more people received medical attention for dehydration than hypernatremia during the event from 2001 to 2008.

Written by Jen Matz.

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