Ask Dr. Lisa

Q: Can you drink too much water?

A: It's pretty difficult to overdose on water. In fact, the eight-glass-a-day rule is just a rough estimate, and many people need more than that, especially if theyr'e active. You can meet your fluid requirements with fruit and veggie juices as well as almost any noncaffeinated beverage. The easiest way to know if you're getting enough? Monitor your urine. If it's pale yellow and you pee every two to four hours, you're drinking plenty of water. Of course, there is one way to OD on H ₂ O: If you exercise and sweat for several hours in a row and drink only water, you could dilute your sodium levels, which can lead to weakness, nausea, confusion and, very rarely, coma. The fix is easy, though: Just down a sports drink or eat a meal that includes something salty.

Lisa Callahan, M.D., is the author of The Fitness Factor (The Lyons Press). Have a personal health question? Write to drlisa@self.com.