Dehydration occurs when your body does not have as much water and fluids as it needs.

Dehydration can be mild, moderate, or severe, based on how much of your body's fluid is lost or not replaced. Severe dehydration is a life-threatening emergency.

Vomiting - dehydration; Diarrhea - dehydration; Diabetes - dehydration; Stomach flu - dehydration; Gastroenteritis - dehydration; Excessive sweating - dehydration

You can become dehydrated if you lose too much fluid, do not drink enough water or fluids, or both.

Your body may lose a lot of fluid from:

• Sweating too much, for example, from exercising in hot weather
• Fever
• Vomiting or diarrhea
• Urinating too much (uncontrolled diabetes or some medicines, like diuretics, can cause you to urinate a lot)

You might not drink enough fluids because:

• You do not feel like eating or drinking because you are sick
• You are nauseated
• You have a sore throat or mouth sores

Older adults and people with certain diseases, such as diabetes, are also at higher risk for dehydration.

Signs of mild to moderate dehydration include:

• Thirst
• Dry or sticky mouth
• Not urinating much
• Darker yellow urine
• Dry, cool skin
• Headache
• Muscle cramps

Signs of severe dehydration include:

• Not urinating, or very dark yellow or amber-colored urine
• Dry, shriveled skin
• Irritability or confusion
• Dizziness or lightheadedness
• Rapid heartbeat
• Rapid breathing
• Sunken eyes
• Listlessness
• Shock (not enough blood flow through the body)
• Unconsciousness or delirium

Your health care provider will look for these signs of dehydration:

• Low blood pressure.
• Blood pressure that drops when you stand up after lying down.
• White finger tips that do not return to a pink color after your provider presses the fingertip.
• Skin that is not as elastic as normal. When the provider pinches it into a fold, it may slowly sag back into place. Normally, skin springs back right away.
• Rapid heart rate.

Your provider may do lab tests such as:

• Blood tests to check kidney function
• Urine tests to see what may be causing dehydration
• Other tests to see what may be causing dehydration (blood sugar test for diabetes)

To treat dehydration:

• Try sipping water or sucking on ice cubes.
• Try drinking water or sports drinks that contain electrolytes.
• Do not take salt tablets. They can cause serious complications.
• Ask your provider what you should eat if you have diarrhea.

For more severe dehydration or heat emergency, you may need to stay in a hospital and receive fluid through a vein (IV). The provider will also treat the cause of the dehydration.

Dehydration caused by a stomach or intestinal virus should get better on its own after a few days.

If you notice signs of dehydration and treat it quickly, you should recover completely.

Untreated severe dehydration may cause:

• Death
• Permanent brain damage
• Seizures

You should call 911 or the local emergency number if:

• The person loses consciousness at any time.
• There is any other change in the person's alertness (for example, confusion or seizures).
• The person has a fever over 102°F (38.8°C).
• You notice symptoms of heatstroke (such as rapid pulse or rapid breathing).
• The person's condition does not improve or gets worse despite treatment.

To prevent dehydration:

• Drink plenty of fluids every day, even when you are well. Drink more when the weather is hot or you are exercising.
• If anyone in your family is ill, pay attention to how much they are able to drink. Pay close attention to children and older adults.
• Anyone with a fever, vomiting, or diarrhea should drink plenty of fluids. DO NOT wait for signs of dehydration.
• If you think you or someone in your family may become dehydrated, call your provider. Do this before the person becomes dehydrated.

Kenefick RW, Cheuvront SN, Leon LR, O'Brien KK. Dehydration and rehydration. In: Auerbach PS, Cushing TA, Harris NS, eds. Auerbach's Wilderness Medicine. 7th ed. Philadelphia, PA: Elsevier; 2017:chap 89.

Padlipsky P, White W. Pediatric infectious diarrheal disease and dehydration. In: Walls RM, ed. Rosen's Emergency Medicine: Concepts and Clinical Practice. 10th ed. Philadelphia, PA: Elsevier; 2023:chap 167.