To prevent dehydration, drink plenty of fluids and eat foods high in water such as fruits and vegetables. Letting thirst be your guide is an adequate daily guideline for most healthy people. Fluids can be obtained not just from water but also from other beverages and foods. But, if you're exercising, don't wait for thirst to keep up with your fluids.

Under certain circumstances, you may need to take in more fluids than usual:

  • Illness. Start giving extra water or an oral rehydration solution at the first signs of illness — don't wait until dehydration occurs. And although they might sound appealing, traditional "clear fluids" such as ginger ale or other sodas contain too much sugar and too little sodium to replenish lost electrolytes.
  • Exercise. In general, it's best to start hydrating the day before strenuous exercise. Producing lots of clear, dilute urine is a good indication that you're well hydrated. Before exercising, drink 1 to 3 cups (0.24 to 0.70 liters) of water. During the activity, replenish fluids at regular intervals and continue drinking water or other fluids after you're finished.

    Keep in mind that drinking too much not only can cause bloating and discomfort but also may lead to a potentially fatal condition in which your blood sodium becomes too low (hyponatremia). This occurs when you drink more fluids than you lose through sweating.

  • Environment. You need to drink additional water in hot or humid weather to help lower your body temperature and to replace what you lose through sweating. You may also need extra water in cold weather if you sweat while wearing insulated clothing. Heated, indoor air can cause your skin to lose moisture, increasing your daily fluid requirements. And altitudes greater than 8,200 feet (2,500 meters) also can affect how much water your body needs. If dehydration occurs when you're exercising in hot weather, get into a shady area, recline, and start drinking water or a sports drink. Young athletes should be encouraged to let their coaches know if they're having symptoms of dehydration.
Feb. 12, 2014