We’re a nation hooked on hydration: We stash water bottles in our purses and gym bags, stock up on them in our offices and cars, wash down meals with the stuff and urge our kids to guzzle frequently too. Certainly it’s important to get plenty of fluids throughout the day, especially when it’s steamy out and during exercise.

Related: The Right Way to Wash Your Water Bottle

But it’s also possible to down too much water, with dire consequences. Besides the toll disposable water bottles take on the environment, water intoxication, aka hyperhydration (or more scientifically, dilutional hyponatremia), can lead to a potentially dangerous electrolyte imbalance.

“In order for enzymes and cells to stay alive, the body has to maintain certain levels of electrolytes, including sodium, potassium, calcium and magnesium. Too much water can throw these levels off,” explains Thomas Trojian, MD, a sports medicine physician in Philadelphia and past board member of the American Medical Society for Sports Medicine.

“Each day a person should consume enough water and electrolytes, as well as carbs, protein and fat, to replace losses and provide energy,” adds Holly Benjamin, MD, a sports medicine physician and professor at the University of Chicago’s School of Medicine. This way, the body keeps a solid equilibrium or homeostasis.

Excessive consumption of water, especially in a short amount of time, puts severe stress on the body and can act as a poison. “Water intoxication results in a steep drop in sodium levels, which unleashes a cascade of fluid imbalances and swelling, causing the body to malfunction,” says Benjamin.

Symptoms of hyperhydration include nausea, vomiting, confusion, slurred speech, labored breathing, fatigue, blurry vision, cramping, spasms, seizures and even death.

Here’s what else you should know about water intoxication:

Who’s at risk of water intoxication

“Children, elderly people and endurance athletes who consume large amounts of fluid during prolonged intense exercise seem to be at the highest risk for hyponatremia,” says Benjamin.

Even babies can be affected, especially those under a year old, according to the St. Louis Children’s Hospital. In general, infants need only breast milk or formula to stay healthy and hydrated. Tiny tykes are at risk because their small body mass makes it easy to take in large amounts of water relative to their size.

“Typically the kind of person who develops water intoxication is the slow marathon runner who’s trying to avoid dehydration by overcompensating and ends up taking a cup at every water station,” says Troijan. But anyone who drinks excessively in a short period of time can become way too hydrated — you don’t need to be out running,” reminds Benjamin.

Related: Is It Safe to Drink the Water on a Plane?

How it’s treated

A mild case of overhydration can be eased by restricting water and other fluids. “Sometimes patients are advised to eat a salty snack, like pretzels. Occasionally diuretics are used to increase urination,” says Benjamin.

The drug vasopressin can be used to regulate fluid balance at the cellular level; a more severe case of hyperhydration may require intravenous hydration treatment with concentrated sodium chloride.

Ways to prevent it

If you’re an avid runner, it may be time to become familiar with the color of your urine. “Light yellow is the optimal hue,” says Trojian. Nearly clear means you’ve had too much water, while dark yellow or a brownish shade can indicate dehydration.

Use common sense when it comes to drinking during exercise, particularly on hot summer days. “For runs under an hour, water is perfect, but if you go longer, electrolytes and a small amount of carbs should be added,” he says.

You also can use a scale to monitor hydration: Weigh yourself before and after physical activity (naked, dried off) and note the difference. Every kilogram of weight loss equals one liter of water (or for every pound lost, you’ll need just under 16 oz). Most people can down from 1 to 1½ quarts of water a day, depending on height, weight and other health factors. Drinking more than 72 oz of water a day is generally not recommended.

Besides keeping tabs on how much water you take in, pay attention to what you put out: Make sure you hit the bathroom every two hours and that your urine is clear yellow, says Benjamin. 

Related: 7 Signs You Need a Drink of Water

Jennifer Kelly Geddes is a New York City-based writer and editor who specializes in parenting, health and child development. She’s also the mom of two teen girls.