Dear Dr. Katz:
I started drinking more water about 12 years ago because I heard it was healthy. But now I'm up to three liters a day, and I'm always thirsty. Should I be concerned?
You're right that drinking water is good for your health. Staying well hydrated maintains healthy circulation, reduces risk of kidney stones, and helps the liver remove toxins from the body, among other benefits. As for how much to imbibe, that's not so apparent.
The "drink eight 8-ounce glasses of water a day" mandate is more of an old wives' tale than medical fact. The amount each person needs varies with size and activity level as well as weather conditions and water loss in bodily fluids such as sweat and urine. Urine, in fact, is a good gauge of hydration: When nature calls more than once every two hours and the fluid is clear, that's a sign of water overload; a dark yellow color, on the other hand, probably means you're not getting enough.
With your three liters a day, you may just be a person whose body likes a lot of water. But excessive thirst can signal diseases such as diabetes, so I would recommend that you see a doctor about your blood sugar. A simple test can put your mind at ease.