Water is your body’s principal chemical component and makes up about 50% to 70% of your body weight. Your body depends on water to survive.
Every cell, tissue and organ in your body needs water to work properly. For example, water:
- Gets rid of wastes through urination, perspiration and bowel movements
- Keeps your temperature normal
- Lubricates and cushions joints
- Protects sensitive tissues
Lack of water can lead to dehydration — a condition that occurs when you don’t have enough water in your body to carry out normal functions. Even mild dehydration can drain your energy and make you tired.
The U.S. National Academies of Sciences, Engineering, and Medicine determined that an adequate daily fluid intake is:
- About 15.5 cups (3.7 liters) of fluids a day for men
- About 11.5 cups (2.7 liters) of fluids a day for women
These recommendations cover fluids from water, other beverages and food. About 20% of daily fluid intake usually comes from food and the rest from drinks.
Most healthy people can stay hydrated by drinking water and other fluids whenever they feel thirsty. For some people, fewer than eight glasses a day might be enough. But other people might need more.
You might need to modify your total fluid intake based on several factors:
- Exercise. If you do any activity that makes you sweat, you need to drink extra water to cover the fluid loss. It’s important to drink water before, during and after a workout.
- Environment. Hot or humid weather can make you sweat and requires additional fluid. Dehydration also can occur at high altitudes.
- Overall health. Your body loses fluids when you have a fever, vomiting or diarrhea. Drink more water or follow a doctor’s recommendation to drink oral rehydration solutions. Other conditions that might require increased fluid intake include bladder infections and urinary tract stones.
- Pregnancy and breast-feeding. If you are pregnant or breast-feeding, you may need additional fluids to stay hydrated.