Can You Drink Too Much Water? Exploring Overhydration

When you think about “having too much to drink,” chances are you’re not thinking about overdoing it on water. We hear so much about drinking enough water these days that it might seem like there’s no such thing as overhydrating. It’s true, of course, that hydration is a top priority for well-being, but there’s a lesser-known flip side to this health advice. Consuming too much water in too short a time can actually be dangerous—or even deadly.

Recently, multiple news stories have cropped up about people who have died of so-called “water intoxication.” High temperatures and grueling fitness challenges appear to have fueled folks to consume more fluids than their kidneys can handle, causing sodium levels to dip so low as to lead to death.

While experiencing health problems or dying from overhydration is, admittedly, rare, it’s important to realize that, when it comes to water, more isn’t always better. Here’s what to know about getting enough, not guzzling too much.

To maintain proper fluid levels, your body is constantly calibrating a delicate balance of electrolytes. For a quick refresher: electrolytes are electrically charged elements that keep fluid at the right levels inside your cells. These include sodium, potassium, magnesium, chloride, and others. You probably know you can lose electrolytes through sweat—hence the common recommendation to drink electrolyte replacement beverages after long exercise sessions.

The problem is, if you lose too many electrolytes and attempt to rehydrate with copious amounts of water (which doesn’t contain electrolytes), you run the risk of diluting your blood to a dangerous point. This can ultimately create a condition called hyponatremia.

From the Latin “hypo” (meaning “not enough”) and “natrium” (meaning “sodium”), hyponatremia is defined as a serum sodium concentration of 135 mEq/L. (Normal blood sodium levels are typically from 136-145 mEq/L.) With too much water and not enough sodium in the blood, your body can’t perform essential functions. And when you don’t have enough sodium to control fluid levels, excess water can enter the brain cells, causing life-threatening brain swelling.

Again, overhydration is considered rare—you’re far more likely to become dehydrated than overhydrated—but knowing its causes and risk factors can help you avoid it.

For starters, having a health condition that causes water retention puts you at higher risk of overhydration, since your kidneys may not be able to flush out water effectively. Health issues like kidney disease, congestive heart failure, liver disease, and uncontrolled diabetes can all raise the risk of water intoxication. Some medications do the same. Antihypertensives, corticosteroids, and non-steroidal anti-inflammatory drugs (NSAIDs) are all known to cause fluid retention. Drinking extreme amounts of water while on these meds or living with these conditions could lead to dangerously low electrolyte levels.

Often, however, water intoxication has less to do with a health condition and more to do with your activity level. It frequently occurs after participating in a high-intensity athletic event. “People who drink too much water while taking part in marathons, ultramarathons, triathlons, and other long-distance, high-intensity activities are at an increased risk of hyponatremia,” says dietitian and personal trainer Wan Na Chun, MPH, RD, CPT.

It makes sense, of course. After sweaty, strenuous exercise, we’re driven to replenish our body’s fluid stores. But losing electrolytes through sweat and flushing your system with tons of water can be a dangerous combo. “Long durations of exercise paired with too much water can put you at risk for hyponatremia because you lose sodium as you sweat,” says Jamie Nadeau, RD. “If you’re exercising for longer than an hour, it’s a good idea for most people to include a drink that has electrolytes, like sodium.”

The signs of overhydration can start subtly. After drinking a large amount of water (especially with a health condition or after an endurance event like a marathon), you could experience nausea, headache, confusion, vomiting, muscle cramps, or swelling. It may initially be difficult to tell these symptoms apart from overexertion.

Left untreated, though, water intoxication may progress to more serious neurological effects. As the brain cells swell with too much water, it can lead to coma and even death.

If you think you might be glugging a bit too much, pay attention to physical cues like how often you’re urinating and the color of your urine. Going to the bathroom more than once every couple of hours or having totally clear urine could be signs of overhydration.

Physical signs and symptoms are a helpful indicator of water intoxication, but the most reliable diagnostic tool is a blood test. This can determine whether your sodium levels have dipped into the danger zone of hyponatremia. Some doctors may also use a urine test to diagnose the condition.

If it turns out you do have water intoxication, your treatment options vary. “The typical treatment approach to overhydration/hyponatremia depends on the severity of the condition,” says Chun. “Mild cases can be treated by reducing fluid intake, while more severe cases may require intravenous fluids or medications to help balance electrolyte levels.” 

Since underlying conditions can make you more susceptible to overhydration, your doctor may also do additional testing to determine whether you’re having a problem with your kidneys, heart, or liver.

We all want to hit that Goldilocks level of just enough and not too much water. For optimum health, start by listening to your body’s cues. Drinking to your level of thirst is usually a reliable means of properly hydrating. 

When in doubt, you can also stick to public health guidelines for hydration. “In general, men need about 15.5 cups of water per day and women need about 11.5 cups of water per day, so if you’re drinking more than that, it’s worth evaluating why,” says Nadeau.  

Remember, too, that downing an entire day’s worth of water in one sitting isn’t the goal. “It’s important to make sure that you’re spacing that water throughout the day consistently and not just chugging it all in a small window,” Nadeau notes. “The CDC recommends no more than 48 ounces of water per hour.”

And don’t forget that water isn’t the only way to hydrate. Balancing your H2O intake with hydrating foods like soups, popsicles, and fruit adds to your daily fluid total while often upping electrolytes. There’s definitely a time and place for electrolyte drinks, too. Whether it’s a sports beverage, juice, or even a glass of milk, electrolyte-rich drinks ensure that you’re hydrating well without risking dangerous imbalances.