The Definitive Guide to How Much Water You Should Drink

Somewhere more than zero and less than 20 liters*

It’s just about the easiest, safest medical advice you can give: “drink more water”. You have a headache? Drink more water. Tired? Drink more water. Cold coming on? Drink more water. Tom Brady famously attributed his QB longevity to water drinking, among some other less… ordinary practices.

I’m a nephrologist — a kidney doctor. I think about water all the time. I can tell you how your brain senses how much water is in your body and exactly how it communicates that information to your kidneys to control how dilute your urine is. I can explain the miraculous ability of the kidney to concentrate urine across a range from 50 mosm/L to 1200 mosm/L — and the physiology that makes it all work.

But I can’t really tell you how much water you’re supposed to drink.

And believe me, I get asked all the time.

There are a couple things I’m sure of when it comes to water. You need to drink some.

Though some animals, like Kangaroo rats, can get virtually all the water they need from the food they eat, we are not such animals. Without water, we die.