How much water should you drink a day?

Eight glasses a day? More or less? The amount of water we need to drink each day can vary.

The August issue of Mayo Clinic Women's HealthSource lists factors that can increase the need for fluid, including:

• Increased physical activity
• Hot and humid weather
• Dry indoor air and high altitudes, which reduce moisture in the air
• Having an illness, particularly one accompanied by fever, vomiting or diarrhea

Data show that women who are adequately hydrated consume about 2.7 liters (91 fluid ounces) of total water a day. Since food typically accounts for about 20 percent of fluid intake, this means drinking roughly 2.2 liters (74 ounces or about 9 cups) of beverages a day.

While drinking water is often the best way to replace lost fluids, other liquids including milk, tea, soup, fruit juice and sports drinks also are effective. One caution: beverages with caffeine or alcohol can increase fluid output, making it more difficult to stay adequately hydrated.

For a healthy adult, fluid intake is probably adequate when one rarely experiences thirst and when urine is colorless or slightly yellow. As adults get older, they may experience less thirst, so it's advised to drink before thirst sets in. Signs of inadequate fluid intake may include dry mouth, headache, light-headedness, little or no urination, and constipation.