Dehydration

The body not having enough water and other fluids is very risky for infants, young children and older adults.

Update Date: 02.05.2025

Overview
Symptoms
Causes
Risk factors
Complications
Prevention
Diagnosis
Treatment
Preparing for your appointment
Overview
Symptoms
Causes
Risk factors
Complications
Prevention
Diagnosis
Treatment
Preparing for your appointment

Overview

Dehydration occurs when the body uses or loses more fluid than it takes in. Then the body doesn't have enough water and other fluids to do its usual work. Not replacing lost fluids leads to dehydration.

Anyone can become dehydrated. But the condition is more serious for infants, children and older adults.

The most common cause of dehydration in young children is diarrhea and vomiting. Older adults have a lower volume of water in their bodies to begin with. And older adults might have conditions or take medicines, such as water pills, that increase the risk of dehydration.

Dehydration also can occur in anyone who doesn't drink enough water during hot weather. It's more likely in people who are active in the heat.

Drinking more fluids usually fixes mild to moderate dehydration. But severe dehydration needs medical treatment right away.

Symptoms

Thirst isn't always a good way to tell if the body needs water. Many people, mainly older adults, don't feel thirsty until they're dehydrated. That's why it's important to increase water intake during hot weather or while ill.

The symptoms of dehydration can differ by age.

Infant or young child

  • Urinating less than usual or no wet diapers for three hours.
  • Dry mouth.
  • No tears when crying.
  • Rapid heart rate.
  • Sunken eyes, cheeks or soft spot on top of the skull.
  • Lacking energy or being cranky.
  • Skin that doesn't flatten back right away after being pinched.

Adult

  • Extreme thirst.
  • Urinating less.
  • Dark-colored urine.
  • Tiredness.
  • Dizziness.
  • Being confused.
  • Skin that doesn't flatten back right away after being pinched.
  • Sunken eyes or cheeks.

When to see a doctor

Call your family healthcare professional if you or a loved one:

  • Has had diarrhea for 24 hours or more.
  • Is cranky or confused.
  • Is sleepier or less active than usual.
  • Can't keep down fluids.
  • Has bloody or black stool.
  • Has a fever of 102 degrees or higher.

Causes

Sometimes dehydration occurs for simple reasons. These include not drinking enough water. This can happen when you're sick or too busy to remember to drink enough. Or there might be no safe water to drink when traveling, hiking or camping.

Other dehydration causes include:

  • Diarrhea and vomiting. Diarrhea that comes on suddenly and hard can cause a huge loss of water and minerals the body needs, called electrolytes, in a short time. Vomiting with diarrhea causes the loss of even more fluids and minerals.
  • Illnesses that cause fever.

    In general, the higher the fever, the more severe dehydration might be. The problem is even worse when there's fever plus diarrhea and vomiting.

    Even without a fever, people who have a cold or sore throat are less likely to feel like eating or drinking. This can lead to dehydration.

  • Weather and activities that cause sweating. Sweating causes fluid loss. Replacing fluids during hard activity is needed to keep from dehydrating. Hot, humid weather increases the amount of sweat and fluid lost.
  • Medicines. Certain medicines cause more urination, which can lead to dehydration. These include water pills, called diuretics, and some blood pressure medicines.
  • Diabetes. Diabetes that hasn't been diagnosed or isn't controlled can lead to dehydration.

Risk factors

Anyone can get dehydrated. But certain people are at greater risk. They include:

  • Infants and children. This group is most likely to have bad diarrhea and vomiting, which can lead to dehydration. They also lose a lot of fluids from high fevers or burns. Young children often can't say that they're thirsty. Nor can they get a drink for themselves.
  • Older adults. With aging, the body's fluid reserve becomes smaller. The ability to hold on to water is reduced. And older people are less likely to feel thirsty.

Adding to these problems can be illnesses such as diabetes and dementia and taking certain medicines. Some older people might not be able to get water for themselves.

Complications

Dehydration can lead to serious complications, including:

  • Heat injury. People who don't drink enough fluids when they're exercising hard and sweating a lot might end up with a heat injury. Heat injuries range from mild heat cramps to heat exhaustion or heatstroke, which can be deadly.
  • Urinary and kidney problems. Long-lasting or repeated bouts of dehydration can cause urinary tract infections, kidney stones and even kidney failure.
  • Seizures. Electrolytes, such as potassium and sodium, help carry electrical signals from cell to cell. If electrolytes are out of balance, the signals they send can get mixed up. This can cause muscles to tighten or shorten. It also can cause passing out.
  • Low blood volume shock, called hypovolemic shock. This is one of the most serious complications of dehydration. It can be deadly. It occurs when low blood volume causes a drop in blood pressure and a drop in the amount of oxygen in the body.

Prevention

To keep from getting dehydrated, drink fluids and eat foods that hold a lot of water, such as fruits and vegetables. Don't drink fluids that have caffeine or a lot of sugar, such as sodas and some energy drinks. They can be dehydrating.

Conditions that can create a need for more fluids include:

  • Vomiting or diarrhea. Children who are vomiting or have diarrhea need extra water at the first signs of illness. Or they need a drink that replaces water, sugar and electrolytes, called an oral rehydration solution. Don't wait until dehydration occurs.
  • Hard exercise. In general, it's best to start drinking more fluids the day before hard exercise. Making lots of clear urine is a good sign of being well hydrated. During the activity, drink fluids regularly. Continue to drink water or other fluids when the activity is over.
  • Hot or cold weather. Drinking more water in hot or humid weather helps lower body temperature and replaces water lost through sweating. In cold weather, extra water can help prevent combat moisture loss from dry air. This might be most needed at higher altitudes.
  • Illness. Older adults can get dehydrated during minor illnesses. These include the flu, bronchitis or bladder infections. Make sure to drink extra fluids when you don't feel well.

Diagnosis

A healthcare professional often can diagnose dehydration from symptoms. For a child, a change in weight might be used in the diagnosis.

To help confirm the diagnosis and to find out how dehydrated you are, you may have other tests. These might include:

  • Blood tests. Blood samples check for several things. These include the levels of electrolytes, especially sodium and potassium, and how well the kidneys are working.
  • Urinalysis. Tests done on your urine can help show whether you're dehydrated and how much. They also can check for a bladder infection.

Treatment

The only way to treat dehydration is to replace lost fluids and lost electrolytes. The best way to replace lost fluids depends on age, how bad the dehydration is and its cause.

For infants and children who are dehydrated from diarrhea, vomiting or fever, use water with electrolytes such as Pedialyte or Smart Water.

Start with about a teaspoon (5 milliliters) every 1 to 5 minutes and increase as your child is able to take it. It might be easier to use a syringe for very young children. Older children can drink watered-down sports drinks, such as Gatorade or Powerade. Use 1 part sports drink to 1 part water.

Most adults with mild to moderate dehydration from diarrhea, vomiting or fever can get better by drinking more water or other liquids. For children and adults, drinking full-strength fruit juice and soft drinks might make diarrhea worse.

If you work or exercise outdoors during hot or humid weather, drink cool water. Sports drinks that have electrolytes and a carbohydrate solution also may be helpful.

Severe dehydration should be treated right away, either by emergency workers who come in an ambulance or in a hospital emergency room. Salts and fluids given through a vein, called intravenously, are absorbed quickly and speed recovery.

Preparing for your appointment

You're likely to start by seeing your or your child's family healthcare professional. If you or your child shows signs of serious dehydration, such as having no energy or not responding to others, seek immediate care at a hospital right away.

If you have time to prepare for your appointment, here's some information to help you get ready.

What you can do

Make a list of:

  • Symptoms and when they began. If there's been vomiting or diarrhea, write down when it began and how long it lasted.
  • Key personal information, including recent travel or foods eaten that might have caused illness.
  • Key medical information, including other conditions. List all medicines, vitamins and supplements, as well as doses.
  • Questions to ask at your appointment.

For dehydration, questions might include:

  • What's causing these symptoms?
  • What tests are needed?
  • What treatment do you recommend?
  • How long will it take to get better?
  • What can prevent dehydration from happening again?

What to expect from your doctor

Your healthcare professional is likely to ask questions, such as:

  • What were you doing when the symptoms began?
  • Can you keep down food or drink?
  • When did you last urinate? Do you have pain with urination or feel like you have to urinate right away?
  • Are there other symptoms, such as belly cramping, fever, headache or muscle aches? How bad are these symptoms?
  • Has there been blood in the stools?

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