Many people are aware of the dangers of not drinking enough water, but can you drink too much water? The surprising answer is yes. It's rare to overdose on water, but it is possible, which leads to the inevitable question: How much water is too much?
The problem with guzzling water is that if you overdo it, you can wind up with a condition known as hyponatremia. This is when the sodium level in your blood is too low. Your kidneys do a good job of getting rid of excess water, but if you're consuming water at a faster rate than your kidneys can excrete it, the extra water dilutes the sodium in your bloodstream, leading to hyponatremia.
Because most people have no idea you can drink too much water, they're unfamiliar with the symptoms of hyponatremia. According to the Mayo Clinic, confusion and headache; drowsiness and fatigue; nausea and vomiting; muscle spasms, cramping, or weakness; and irritability are all signs that your sodium levels are too low. In some cases, a person with hyponatremia can experience seizures and even fall into a coma. If you or someone you know is experiencing severe symptoms, visit an emergency room right away.
Hyponatremia is often associated with endurance sports, as athletes competing in these events often drink too much water to ward off possible dehydration. The elderly are also susceptible to hyponatremia, according to a 2017 article published in the journal Clinical Interventions in Aging. But you don't have to be a marathon runner to experience hyponatremia. It's often the case that a person ends up with hyponatremia as a result of drinking too much water too quickly. According to a June 2013 study published in the journal Annals of Pediatric Endocrinology & Metabolism, the kidneys can only excrete between 800 and 1,000 mililiters (27 to 33 ounces) each hour — so don't drink more water than that in a 60-minute window.
Now that you're aware of the dangers of drinking too much water, we're not giving you the OK to avoid any water. The kidneys can excrete between 20 and 28 liters of water in a day, according to that 2013 study. That means your little kidneys can handle between roughly five and seven gallons of water, which is a lot for one person, considering that the National Academies of Sciences, Engineering, and Medicine determined that 15.5 cups (3.7 liters) for men and 11.5 cups (2.7 liters) for women were adequate daily targets.
It's summer and it's hot, which means you should be drinking water — and lots of it. Just make sure that you're not overhydrating simply because there's some H2O nearby. A 2017 study published in the journal Frontiers in Medicine found that drinking according to when you were thirsty was a safe and effective method for preventing hyponatremia in endurance athletes. Why not adopt that same rule?