Besides shriveling up like a raisin and, um, dying, you might already know what happens when you don't drink enough water. You get cranky, feel low-energy, and on and on.
So you definitely need to stay hydrated. Chug, chug, chug! Actually, slow your guzzle: it is possible to overdo it. But how do you know when it's time to put the bottle down, aside from all the pee breaks?
What are the signs of "water intoxication"?
It's a real thing, for starters! And less fun than other varieties of intoxication -- too much H2O can be deadly. Overhydrating can lead to some nasty effects if you're not careful, and while early stages don't always have prominent symptoms, confusion, disorientation, headaches, nausea, and vomiting all can point to a problem.
Longer-term symptoms can include muscle weakness, seizures, and even comas. Obviously these outcomes are rare, otherwise you'd hear constant warnings not to drink too much water. "You have to drink A LOT of water to get to this point, though," says Dr. Nicole Van Groningen. "Liters and liters over a short period of time. A normal kidney can excrete about half a liter an hour, at most. If you're drinking substantially more than this, you're putting yourself at risk for water intoxication."
It's less about the water, more about the salt
Hyponatremia is a condition in which the sodium level of the blood drops. Simple seventh-grade science class covered what happens when we add too much water to a mixture: you dilute it. Same thing happens when you over-imbibe water. "When you drink too much water, you dilute your blood and end up not having enough of your body's natural salt," says Dr. Lisa Ashe.
"Eventually, if it drops too low, water rushes into cells," Dr. Van Groningen warns, adding that this can lead to swelling of brain cells, resulting in all those terrible aforementioned symptoms. This condition, somewhat ironically, can affect ultra-distance athletes who are so concerned about maintaining their hydration levels that they constantly drink water, dropping their sodium levels in the process.