What is dehydration?


Dehydration: Overview

Dehydration happens when your body loses too much fluid. This might happen when you do not drink enough water or you lose large amounts of fluids from your body because of diarrhea, vomiting, or sweating. Severe dehydration can be life-threatening.

Water and minerals called electrolytes help put your body fluids back in balance. Learn the early signs of fluid loss, and drink more fluids to prevent dehydration.


Severe dehydration means:

  • Your mouth and eyes may be extremely dry.
  • You may pass little or no urine for 12 or more hours.
  • You may not feel alert or be able to think clearly.
  • You may be too weak or dizzy to stand.
  • You may pass out.
Severe dehydration is a medical emergency and requires emergency treatment. Call 911 or other emergency services immediately.

Moderate dehydration means:

  • You may be a lot more thirsty than usual.
  • Your mouth and eyes may be drier than usual.
  • You may pass little or no urine for 8 or more hours.
  • You may feel dizzy when you stand or sit up.

Mild dehydration means:

  • You may be more thirsty than usual.
  • You may pass less urine than usual.

Mild to moderate dehydration is treated at home by drinking more fluids. Treatment for moderate to severe dehydration may include I.V. fluids and a stay in the hospital.

Dehydration is very dangerous for babies, small children, and older adults. It is most dangerous for newborns. Watch closely for early symptoms anytime there is an illness that causes a high fever, vomiting, or diarrhea.

What are the signs of dehydration in a child?

As your child becomes dehydrated, thirst increases, and their mouth or eyes may feel or look very dry. Your child may also lack energy and want to be held a lot. Your child will not urinate as often as usual.

Helping your child avoid dehydration and heat exhaustion with sports

When your child is active and not drinking enough fluids, dehydration is a risk. The muscles get tired quickly. Your child may have leg cramps while walking or running. Playing hard and sweating without drinking fluids can cause dehydration and heat exhaustion.

To prevent this, teach your child these tips.

  • Do activities during the coolest parts of the day.
  • Drink water throughout the day, every day.
  • Drink extra water before, during, and after exercise.
  • Take breaks and drink at least every 15 to 20 minutes during exercise.
  • Stop and rest if you get dizzy or lightheaded or feel very tired.
  • Wear clothes that help cool the body.

How can you care for yourself when you are dehydrated?

  • Drink plenty of fluids. Choose water and other clear liquids until you feel better. If you have kidney, heart, or liver disease and have to limit fluids, talk with your doctor before you increase the amount of fluids you drink.
  • If you do not feel like eating or drinking, try taking small sips of water, sports drinks, or other rehydration drinks.
  • Get plenty of rest.

To prevent dehydration

  • Add more fluids to your diet and daily routine, unless your doctor has told you not to.
  • During hot weather, drink more fluids. Drink even more fluids if you exercise a lot. Stay away from drinks with alcohol.
  • Watch for the symptoms of dehydration. These include:
    • A dry, sticky mouth.
    • Not much urine.
    • Dry and sunken eyes.
    • Feeling very tired.
  • Learn what problems can lead to dehydration. These include:
    • Diarrhea, fever, and vomiting.
    • Any illness with a fever, such as pneumonia or the flu.
    • Activities that cause heavy sweating, such as endurance races and heavy outdoor work in hot or humid weather.
    • Certain medicines, such as cold and allergy pills (antihistamines), pills that remove water from the body (diuretics), and laxatives.
    • Certain diseases, such as diabetes, cancer, and heart or kidney disease.

How can you stay hydrated?

  • Take frequent sips of an electrolyte replacement drink. These can be found in grocery stores and drugstores. Examples of these are Pedialyte and Rehydralyte. These replace both fluid and important minerals called electrolytes you need for balance in your blood.
  • Do not drink any alcohol. It can make you dehydrated.
  • Drink plenty of fluids. If you have kidney, heart, or liver disease and have to limit fluids, talk with your doctor before you increase the amount of fluids you drink.

Dehydration in children: When to call

Call 911 anytime you think your child may need emergency care. For example, call if:

  • Your child passed out (lost consciousness).

Call your doctor now or seek immediate medical care if:

  • Your child has symptoms of worsening dehydration, such as:
    • Dry eyes and a dry mouth.
    • Passing only a little urine.
    • Feeling thirstier than usual.
  • Your child cannot keep down fluids.
  • Your child is becoming less alert or aware.
  • Your child has diarrhea that lasts longer than a few days.

Watch closely for changes in your child's health, and be sure to contact your doctor if your child does not get better as expected.

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The content above contains general health information provided by Healthwise, Incorporated, and reviewed by its medical experts. This content should not replace the advice of your healthcare provider. Not all treatments or services described are offered as services by us. For recommended treatments, please consult your healthcare provider.

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