Photo of woman drinking water to prevent dehydration

Condition or Illness – What is dehydration?

Dehydration means your body lacks the amount of fluid needed to support its daily functions.

It can be mild, moderate, or severe based on how much of the body's fluid is lost or not replenished. When it is severe, dehydration is a life-threatening emergency.

Causes of Dehydration

Dehydration can be caused by losing too much fluid, not drinking enough water or fluids, or both.

Your body may lose too many fluids from:

  • Excessive sweating (for example, from exercise)
  • Excessive urination, such as with uncontrolled diabetes or the use of a diuretic
  • Fever
  • Vomiting or diarrhea

You might not drink enough fluids because of:

  • Loss of appetite due to illness
  • Nausea
  • Sore throat or other oral disease or ailments

Dehydration in sick children is often a combination of refusing to eat or drink and losing fluid from vomiting, diarrhea, or fever.

Infants and children are more likely to become dehydrated than adults because they weigh less and their bodies turn over water and electrolytes (minerals in your body fluids) more quickly. The elderly and people with illnesses are also at higher risk.

Signs and Symptoms of Dehydration

Signs and Symptoms of dehydration vary based on the severity of the condition.

Mild symptoms include:

  • Dry or sticky mouth
  • Sensation of thirst
  • Decreased urination
  • Dark tea colored urine
  • Headache
  • Fatigue
  • And dizziness when standing

Moderate symptoms include:

  • Dry or sticky mouth
  • Sunken eyes
  • Confusion
  • Fainting
  • Increase irritability
  • Sleepiness

Severe symptoms include:

  • Increased heart rate
  • Decreased blood pressure
  • Tingling in ones limbs
  • Loss of vision
  • Coma
  • death

Exams and Tests

Physical signs of dehydration include:

  • Loss of skin turgor- the skin may not be as elastic as normal and sag back into position slowly when the health care provider pinches it up into a fold (normally, skin springs right back into place)
  • Low blood pressure or blood pressure that drops quickly when you go from lying down to standing
  • Rapid heart rate
  • Decreased or lack of sweating
  • Decreased or lack of urination

Tests include:

  • Blood chemistries to test levels of electrolytes, blood urea nitrogen (BUN), Creatinin and urine specific gravity

Other tests may be done to determine the cause of the dehydration (for example, blood sugar level to check for diabetes)

Treatment of Dehydration

Drinking fluids is usually enough for mild dehydration. It is better to drink small amounts of fluid often, instead of trying to force large of fluid at one time.

Electrolyte solutions, such as Pedialyte, or freezer pops are very effective.

Stay clear of sports drinks, which contain a lot of sugar and can cause or worsen diarrhea.

IV fluids and a hospital stay may be needed for moderate to severe dehydration. The health care provider will try to identify and then treat the cause of the dehydration.

When to contact medical a professional

Call 911 if you or your child have the following symptoms:

  • Confusion
  • Dizziness
  • Lethargy
  • Light-headedness

Call your health care provider right away if you or your child has any of the following symptoms:

  • Blood in the stool or vomit
  • Diarrhea or vomiting (in infants less than 2 months old)
  • Dry mouth or dry eyes
  • Dry skin that sags back into position slowly when pinched up into a fold
  • Fast-beating heart
  • Little or no urine output for 8 hours
  • No tears
  • Sunken eyes

Also call your health care provider if:

  • You or your child cannot keep down fluids during an illness
  • Vomiting has been going on for longer than 24 hours in an adult or longer than 12 hours in a child
  • Diarrhea has lasted longer than 5 days in an adult or child
  • Your infant or child is much less active than usual or is irritable
  • You or your child is urinating much more than normal, especially if there is a family history of diabetes or you are taking diuretics

Preventing Dehydration

Even when you are healthy, drink plenty of fluids every day. The average adult needs 2800mL (10 cups) of water a day from fluids and foods. Typically, drinking approximately 2000mL (8 cups) combined with normal foods is sufficient to meet daily needs.

  • Drink more water when the weather is extremely hot and when exercising.
  • Thirst is the first sign of mild dehydration so drinking only when thirsty is not enough to meet fluid needs.
  • Carefully monitor someone who is ill, especially an infant, child, or older adult. Begin fluid replacement as soon as vomiting and diarrhea start – do not wait for signs of dehydration.
  • Fluid needs are greater with a fever, vomiting, or diarrhea.

We would like to thank the National Library of Health's MedLine plus for some of the information contained in this article.

Further Information

For more information regarding this topic and others please visit the National Library of Health's MedLinePlus website.