How much water should I drink a day?

Concerns & risks

You were trying to stay healthy and keep hearing you need eight glasses a day.

Too little can lead to dehydration.

Causes & evidence

Needs vary by size, activity and climate. See dehydration.

What to do

1. Drink when thirsty.
2. Check urine color.
3. Drink more in heat and exercise.
4. Talk to your doctor if you have heart or kidney conditions.

Common mistakes: Common mistakes: forcing huge amounts of water. Needs vary by activity, climate and health. Many foods and drinks count. People with some health conditions may need limits, so follow your doctor's advice. A simple check many people use: pale yellow urine generally means you're drinking enough. Carry a reusable bottle and sip through the day rather than chugging. Drink more when it's hot or you're exercising. Water-rich foods like fruit and soup help too. Drinking huge amounts very quickly can be harmful. Thirst, headaches and dark urine are signals to drink more, while needing to pee constantly may mean you're overdoing it. Coffee and tea count toward fluids for most people.

Speed Man tip: Food counts too.

Wrap-up: Needs vary. Use urine color. More in heat.