On a hot summer day, most people expect to feel thirsty after spending time outdoors.

That thirst is your body’s way of reminding you to drink fluids. But what if you don’t feel thirsty? Does that mean you’re well hydrated?

Many people assume thirst is the first sign of dehydration, but that’s not always the case.

In fact, it’s possible to become dehydrated before you ever feel thirsty. This can be especially common in certain groups of people.

Here’s why you shouldn’t rely on thirst to tell you when to drink.