How Quickly Does Your Body Absorb Water After Drinking It?

Q: How much time does it take for the body to absorb water into the system after drinking it?

Photo: Andrea Comi / Moment via Getty

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I’ve always heard that hikers should “drink to their thirst,” but how long does it take for the body to absorb water into the system after drinking it? —Big Gulp

If you like absolute answers, you’ll be disappointed to read water absorption rates vary. Some water is absorbed within seconds to minutes from the mouth and stomach.  After that, the sooner water is emptied from the stomach, the faster it is absorbed, since the maximum rate of absorption occurs in the small intestine. How fast the stomach empties depends on the temp of the water, with cooler water emptying out more quickly. Absorption of water also varies depending on your level of hydration. And there seems to be mystical genetic factor as well.

This is some of the logic behind why we used to tell hikers to “drink before they’re thirsty”—there is a gap, however small, between when you take a drink and when that glorious hydration makes its way into your tissues. But drinking too much water comes with its own risks: Hyponatremia, or water intoxication, occurs when a person consumes too much water within too short of a time, pushing blood sodium levels dangerously low and potentially resulting in confusion, seizures, and even coma or death. So unless you’re an elite athlete, drinking whenever you feel like drinking is going to be the best strategy.

Besides, if you’re thirsty, and you drink a load of water, it’s going to be absorbed pretty darn quick. You can get a rough idea of water absorption rates by sucking down a glass of alcohol, such as whiskey (assuming you’re over 21 of course), and noting how much time elapses before you feel it. It will not be long.

Originally published 2009; last updated January 2022