Skip to Main Content

Welcome to

Together is a new resource for anyone affected by pediatric cancer - patients and their parents, family members, and friends.

Learn More


What is dehydration?

Dehydration happens when the body loses too much water. It can occur when a person does not take in enough liquids or when a person loses too much fluid through vomiting, diarrhea, urine (pee), sweat, or fever.

Dehydration is a common side effect of some illnesses and treatments such as chemotherapy.

The body’s cells need water to function well. Water helps the body:

  • Keep a healthy temperature
  • Take nutrients to cells
  • Get rid of waste
Male toddler sipping from water bottle

Babies and young children are at higher risk for dehydration than adults.

Babies and young children have a higher risk of dehydration than adults. This is because they lose water more quickly than adults.

If not treated, dehydration can lead to severe problems, such as seizures, brain swelling, and kidney failure. Children with medical conditions such as cancer and sickle cell disease are at high risk for complications due to dehydration.

You can often treat dehydration at home. But your child may have to go to the hospital in some cases.

Illustration of water in the body by age

About 80% of a baby's body is made up of water. That amount drops with age.

Symptoms of dehydration

Signs and symptoms of dehydration include:

  • Dry mouth, lips, nostrils, and skin
  • No tears when crying
  • Dizziness, fatigue, or weakness
  • Confusion
  • Irritability
  • Sunken eyes or sunken soft spots on infant's head
  • Little or no urine, dark colored urine
  • Rapid breathing
  • Increased heart rate
  • Low blood pressure
  • Higher than normal body temperature

If your child has dehydration symptoms, contact your care team right away to prevent serious complications.


Causes of dehydration

Causes of dehydration include:

Diagnosis of dehydration

Care providers diagnose dehydration through:

  • Physical exam and health history
  • Blood tests to measure levels of certain electrolytes, such as sodium and potassium. Electrolytes are substances the body needs to properly function.
  • Urine tests

Management of dehydration

The best way to manage dehydration is to prevent it. This lowers your child’s risks for complications. It also reduces the chances of missing or delaying medical procedures and treatments.

Drink water and fluids regularly

Water is best. Ask your care team how much water or fluids your child needs. Your health care provider may also recommend an electrolyte liquid replacement such as Pedialyte® or Enfalyte®.

Your child can also suck on ice chips or popsicles if they have trouble drinking.

If your child does not like to drink water, choose drinks with low sugar and low or no caffeine.

For infants, continue to breastfeed or give infant formula as usual. Follow your health care provider’s directions for feeding.

Manage side effects that cause dehydration

Talk with your care team about ways to prevent or reduce vomiting, diarrhea, and fever. Your child might also have side effects such as mouth or throat sores that make it hard to eat and drink. Your health care provider may prescribe medicines or other treatments.

Treatment of dehydration

You can often treat dehydration at home. Follow your care team’s instructions. Ways to treat dehydration may include:

  • Slowly increase amounts of fluid and food
  • Continue to breastfeed or give formula to infants
  • Keep a record of food and fluid amounts
  • Make sure your child gets plenty of rest
  • Use lotion and lip balm to treat dry skin and lips
  • Watch your child for signs of dehydration that get worse. Your child may need treatment at the hospital.

Hospital care may include:

  • Medicine for fever
  • Rest
  • Tests to monitor electrolytes
  • IV fluids

Once your child is dehydrated, they may need IV fluids to feel better.

Questions to ask the care team

  • Which symptoms of dehydration should I call the care team about?
  • Can my child go to school or daycare?
  • Should my child avoid certain activities? If so, which ones?
  • Are there certain foods or liquids my child should or should not have?
  • Do you recommend any over-the-counter products?
  • Are there any over-the-counter products you do not recommend?

Key points about dehydration

  • Dehydration happens when the body loses too much water.
  • Your body’s cells need water to function well. Water helps the body keep a healthy temperature, take nutrients to cells, and get rid of waste.
  • Dehydration is a common side effect of some illnesses and medical treatments such as chemotherapy. It can happen when your child loses fluid through vomiting, diarrhea, or fever.
  • If your child has cancer or other serious illnesses, getting enough fluids lowers your child’s chances of missing or delaying treatments or procedures.
  • If not treated, dehydration can lead to severe problems. Young children and people with certain medical conditions are at higher risk for health problems due to dehydration.

The Together by St. Jude online resource does not endorse any branded product or organization mentioned in this article.

Reviewed: January 2024