Everyone needs to stay hydrated, but if you're relatively active, it's especially important because your fluid levels can drop quickly. If you don't drink enough, you could become dehydrated and experience fatigue, muscle cramps and even faint in severe cases. There are a few guidelines you can follow to determine how much you should drink; however, in general, if you feel thirsty, you most likely aren't drinking enough.
The Bare Minimum
The Food and Nutrition Board of the Institute of Medicine actually provides a water recommendation for the minimum amount you need: Men need 3.7 liters of water daily, while women should aim for 2.7 liters -- 125 ounces and 91 ounces, respectively. Keep in mind that not all your water intake has to come from chugging water. You'll get about 20 percent of your water needs from the moisture in foods and some from the other beverages you drink as well.
Considering High Activity Levels
You should always drink steadily throughout the day to stay hydrated, particularly if you're highly active. Sip 17 to 20 ounces of water a couple of hours before working out, suggests the American Council on Exercise. Drink another 8 ounces about half an hour before your warm-up. While exercising, you'll need 7 to 10 ounces of water every 10 to 20 minutes. Then after you cool down, aim for another 8 ounces of liquid to replace what you lost. By steadily getting some fluid in your system, you should be able to prevent problems with dehydration.
To get a better understanding of how much fluid you lose through sweating, weigh yourself without any clothes on -- and before you begin your workout. Keep track of how much water you drink while exercising, and then weigh yourself again after. Each pound you lose is equal to approximately 2 cups, or 16 ounces of fluid. So if you are 1 pound lighter after exercising and you drank 16 ounces of water, for example, you lost about 32 ounces of fluid. This is how much you have to drink to get your hydration level back up to par.
While it isn't common, you can drink too much water. If you're an endurance athlete, spending hours running or cycling, you probably drink a lot of water along the way. Even though you're quenching your thirst, you could also be diluting your blood. This condition, called hyponatremia, means that your sodium level is lower than it should be. Initially, you'll feel fatigued, get a headache and have no appetite. But as your blood becomes further diluted, minimizing sodium in your body, you could go through neurological issues like muscle spasms, convulsions or fainting. Prevent hyponatremia during long bouts of exercise by adding a dash of salt to your water bottle or sipping a sports drink.
- Food and Nutrition Board of the Institute of Medicine: Dietary Reference Intakes: Electrolytes and Water
- National Center for Biotechnology Information: Hyponatremia
- National Center for Biotechnology Information: Dehydration
- American Council on Exercise: Healthy Hydration
- Australian Sports Commission: Fluid -- Who Needs It?