It's a warm Saturday afternoon and you've been chasing a soccer ball around the field for what seems like weeks. You're tired, thirsty, and sweaty. As practice wraps up, you have just enough time to duck into the rest room, change your shirt, and slather on a fresh layer of deodorant before heading off to meet your friends for a 4:00 PM movie.

So what's wrong with this picture? You didn't take the time to rehydrate. After all that exercise, your body has lost some fluid and you might be a little dehydrated. Dehydration is a condition that occurs when a person loses more fluids (such as urine or sweat) than he takes in.

To feel your best, you need to replace that fluid. Dehydration is nowhere near as serious a problem for teens as it can be for babies or young children, but if you ignore your thirst, dehydration can slow you down.

Heed That Thirst
When someone gets dehydrated, it means the amount of water in his body has dropped below the proper level (our bodies are about two-thirds water). Small decreases don't cause problems, and in most cases, they go completely unnoticed. There are three levels of dehydration:

• mild (where you can lose 3% to 5% of your body weight)
• moderate (6% to 9%)
• severe (10% or more)

The most common cause of dehydration in teens is gastrointestinal illness, sometimes called the "stomach flu." When you're flattened by the stomach flu, you may lose fluid through vomit and diarrhea. (Gastrointestinal illness is a major cause of dehydration, but anything - food poisoning or an alcohol overload, for example - that makes you throw up several times in a short period of time can dehydrate you.) And if you're spending that much time getting acquainted with the toilet, you probably won't feel like eating or drinking anything.

You can also become dehydrated from lots of physical activity if you don't replace fluid as you go, although it's rare to reach a level of even moderate dehydration during sports or other normal outdoor activity.

Dieting can sap your reserves of water as well because you're changing the balance of what you eat and drink. Beware of diets that emphasize shedding "water weight" as a quick way to lose weight.

Some teen athletes actually dehydrate themselves on purpose to drop weight quickly before a big game or event by sweating in saunas or using laxatives (like Correctol or ex-lax) or diuretics (such as Diurex), which make you urinate more. But that only hurts their performance and can lead to more serious problems, like abnormalities in the salt and potassium levels in the body. Such changes can lead to problems in the heart's rhythm.

Dealing With Dehydration
To counter dehydration, you need to restore the proper balance of water in your body. First, though, you have to recognize the problem. Thirst is the best, and earliest, indicator of potential dehydration.

If you ignore your thirst, after a while you could begin to experience the following symptoms:

• feeling dizzy and light-headed
• dry mouth and nose
• producing less urine when you go to the bathroom

As the condition progresses, you could experience deep, rapid breathing and notice that your eyes are sunken and dry. If a person goes without water for several days, he will grow cold and sweaty, his blood pressure may drop, and his muscles will cramp. Kidney problems can set in, and he might become confused.

The easiest way to avoid any problems - even mild ones - is to drink at least eight glasses of water a day, and more when you're exerting yourself and sweating a lot. That can be tough, especially if it seems like your bladder has the capacity of a teaspoon, but stick to it and you'll feel better in the long run.

When you're sick to your stomach, putting anything in your mouth is probably the farthest thing from your mind, but remember that you still need to drink. Take lots of tiny sips of water, or if you feel up to it, sports drinks, which also replace salts your body has lost.

Stay away from teas, sodas, and coffee, which all usually have caffeine. Caffeine is a diuretic (it makes you urinate more frequently than you usually need to), so it undoes all your hard work. Soda alone is not a good replacement for salts lost due to excessive sweating or illness.

When you're going to be running around outside on a warm day, dress appropriately for the activity. Wear loose-fitting clothes and a hat if you can. That will keep you cooler and cut down on sweating. If you do find yourself feeling parched or dizzy, take a break for a few minutes. Sit in the shade or someplace cool and drink water.

Have you ever spent a warm Sunday afternoon playing basketball or baseball? Chances are, you were thirsty by the end of the game, maybe even thirsty enough to guzzle an entire pitcher of water. That thirst you had was a sign of dehydration (say: dee-hi-dray-shun). Dehydration means that your body loses more fluids (like sweat or urine) than it takes in.

Our bodies need water to work properly. We lose water and some minerals (like salt) from our bodies every day in many ways - through sweating, going to the bathroom, and even through breathing. We usually replace the water we lose through drinking and through the food we eat. But if we lose too much water at once, it can be dangerous.

Could you be dehydrated? Get yourself a glass of water and keep reading to find out!

Why Am I Dehydrated?
Dehydration happens for many different reasons. If you're not drinking enough each day, you might be very thirsty. This is one way your body tells you that it needs more fluids.

Another way to tell that you might be dehydrated is if you feel very tired, even if you're not playing hard and you've been getting enough sleep.

Or you might not be going to the bathroom a lot - maybe only once or twice a day instead of five or six times. That could be another signal that your body needs more water.

You might get dehydrated because you have a virus (say: vye-rus) that makes you vomit, or because you have diarrhea (say: die-ah-ree-ah). This can cause dehydration because your body isn't able to hold onto the water from the things you drink and eat. More fluid and salts come out than you can take or keep in.

Or you might get a cold or the flu. Even if you don't throw up, you might not feel like eating or drinking. And you probably won't have to go to the bathroom very much either. That's why your mom, dad, or doctor will tell you to "drink lots of fluids" when you're sick. They want to make sure you don't get dehydrated.

Another reason you might get dehydrated is because you have been sweating a lot, especially when you play outside in hot weather. Most kids need about twice as much fluid as they usually drink when they're playing sports or exercising. But if you're busy playing, you may forget to stop and take a drink, or to rest and cool down for a while.

Getting too hot can make you dizzy, weak, or nauseated (say: naw-zee-ate-ed), which means that you'll feel like you have to throw up. This is called heat illness, and it can happen when you're dehydrated.

What Should I Do?
The best thing to do when you're dehydrated is to replace the fluids your body has lost. When you're sick, your mom or dad might give you lots to drink to help you do this. Water, Gatorade (and other sports drinks), juices, and even special ice pops can all help your body get the water it needs.

When it's hot outside, and especially when you're exercising, you need to replace the fluids you're losing through sweating. If you get really hot and feel weak or if you can't stand up, get dizzy, or want to throw up, tell an adult and go somewhere cool and rest while you drink.

Do I Need to See a Doctor?
Even if you're thirsty and you do drink while you're sick, you might still keep throwing up. Then your mom or dad might need to take you to your doctor or to the hospital. The doctor will examine you to see why this is happening and to see if you're dehydrated.

The doctor or nurse may set up something called an IV, or intravenous (say: in-trah-vee-nus), line. This is a special tube (like a very thin straw) that goes right into your veins, so the liquid goes right to where your body needs it most. Soon, you will start to feel much better.

If your skin is dry and red, your heart is beating way too fast (like you just ran a race), or you feel confused or really tired, then you need to tell an adult right away. Your mom or dad will need to take you to a doctor or hospital right away.

Thirst-quenching Tips
Whether you're exercising in the sun or keeping it cool by reading on the couch, here's what every kid should know about water:

• Drink water, juice, or sports drinks often when you're playing. Carry a water bottle with you on your bike or in your backpack.
• Drink at least eight glasses of water each day.
• If drinking eight glasses sounds like too much water, try getting some of your water supply from foods like grapes, watermelon, oranges, cantaloupe, lettuce, cucumbers, and celery.
• Drink before you go out to play or exercise.
• Drink even when you're not very thirsty.
• Stay away from drinks that have caffeine (like iced tea or soda, especially colas) when you're exercising - they can actually make you lose more fluids because they make you urinate (pee) more.
• Take plenty of breaks to rest in the shade or in air conditioning. You could also take a bath to cool off, but you still need to remember to drink water.

When you're sick:

• Drink small sips of liquids, even if you really don't feel much like it. If you're not throwing up, ask your mom or dad to make you gelatin or popsicles with your favorite fruit juice.
• Don't drink too fast - this can upset your stomach. Take small sips or even use a spoon to drink just a little bit at a time.
• If you've been throwing up or have diarrhea, be sure to tell a parent. You might have a virus like the flu. Your mom or dad will know when to call the doctor.

The most important thing you can do to prevent dehydration is to pay attention to your body. If you feel really dizzy, weak, or thirsty or if you haven't gone to the bathroom to urinate in the last 8 hours or more, tell an adult right away.

Now that you know all about dehydration, how about getting yourself a refill on that glass of water?

Updated and reviewed by: Kim Rutherford, MD
Date reviewed: June 2001
Originally reviewed by: Steve Dowshen, MD and Kate Cronan, MD