What about the advice to drink 8 glasses a day?

You've probably heard the advice to drink eight glasses of water a day. That's easy to remember, and it's a reasonable goal.

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.