Causes

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

Your body may lose too much fluids from:

• Excessive sweating (for example, from exercise)
• Excessive urine output, such as with uncontrolled diabetes or diuretic use
• Fever
• Vomiting or diarrhea

You might not drink enough fluids because of:

• Loss of appetite due to illness
• Nausea
• Sore throat or mouth sores

Dehydration in sick children is often a combination of refusing to eat or drink anything 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 more quickly. The elderly and people with illnesses are also at higher risk.

Symptoms

• Dry or sticky mouth
• Lethargy or coma (with severe dehydration)
• Low or no urine output; urine looks dark yellow
• No tears
• Sunken eyes
• Sunken fontanelles (the soft spot on the top of the head) in an infant

You may also have vomiting, diarrhea, or the feeling that you "can't keep anything down." All of these can be causing the dehydration.

Exams and Tests

A physical examination may also show signs of:

• Blood pressure that drops when you go from lying down to standing
• Delayed capillary refill
• Low blood pressure
• Poor 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)
• Rapid heart rate
• Shock

Tests include:

• Blood chemistries (to check electrolytes, especially sodium, potassium, and bicarbonate levels)
• Blood urea nitrogen (BUN)
• Complete blood count (CBC)
• Creatinine
• 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

Drinking fluids is usually enough for mild dehydration. It is better to drink small amounts of fluid often (using a teaspoon or syringe for an infant or child), instead of trying to force large amounts of fluid at one time. Drinking too much fluid at once can bring on more vomiting.

Electrolyte solutions or freezer pops are very effective. These are available at pharmacies. Sports drinks contain a lot of sugar and can cause or worsen diarrhea. In infants and children, avoid using water as the primary replacement fluid.

Intravenous 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.

Most cases of stomach viruses (also called viral gastroenteritis) tend to get better on their own after a few days. See also: Diarrhea

See also: Heat emergencies

Outlook (Prognosis)

When dehydration is found and treated quickly, the outcome is usually good.

Possible Complications

Untreated severe dehydration may lead to:

• Death
• Permanent brain damage
• Seizures

When to Contact a Medical 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
• Listlessness and inactiveness
• Little or no urine output for 8 hours
• No tears
• Sunken eyes
• Sunken soft spot on the top of your infant's head

Call your health care provider if you are not sure whether you are giving your child enough fluids.

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

Prevention

Even when you are healthy, drink plenty of fluids every day. Drink more when the weather is hot or you are exercising.

Carefully monitor someone who is ill, especially an infant, child, or older adult. If you believe that the person is getting dehydrated, call your health care provider before the person becomes dehydrated. Begin fluid replacement as soon as vomiting and diarrhea start -- DO NOT wait for signs of dehydration.

Always encourage a person who is sick to drink fluids. Remember that fluid needs are greater with a fever, vomiting, or diarrhea. The easiest signs to monitor are urine output (there should be frequent wet diapers or trips to the bathroom), saliva in the mouth, and tears when crying.

References

Chen L. Infectious diarrheal diseases and dehydration. In: Marx JA, Hockberger RS, Walls RM, et al, eds. Rosen’s Emergency Medicine: Concepts and Clinical Practice. 7th ed. Philadelphia, Pa: Mosby Elsevier; 2009:chap 171.

Greenbaum LA. Deficit therapy. In: Kliegman RM, Behrman RE, Jenson HB, Stanton BF, eds. Nelson Textbook of Pediatrics. 10th ed. Philadelphia, Pa: Saunders Elsevier; 2011:chap 54.

Updated: 4/15/2012

Reviewed by: Linda J. Vorvick, MD, Medical Director, MEDEX Northwest Division of Physician Assistant Studies, University of Washington, School of Medicine. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.