What is dehydration?

How can you know if you are dehydrated?

Every day, we lose body fluids (water and other liquids) in our urine, stool, sweat and tears. We replace the lost fluids by eating and drinking. Normally, the body balances these processes carefully, so we replace as much water as we lose. Certain minerals, such as sodium, potassium, and chloride, are also involved in keeping a healthy fluid balance.

Dehydration (say: dee-hi-DRAY-shun) happens when more fluid leaves the body than enters it. This can happen when a child does not drink enough fluid or when they lose more body fluid than usual. When a child is unwell, fluid can also be lost by vomiting, diarrhea, and fever. The imbalance of losing fluid without replacing it results in dehydration.

Dehydration can happen slowly or quickly, depending on how the fluid is lost and the age of the child. Younger children and babies are more likely to become dehydrated. This is because their bodies are smaller and they have smaller fluid reserves. Older children and teens can more easily handle minor fluid imbalances.

Causes of dehydration

The most common causes of dehydration are:

  • poor fluid intake during an illness

  • fluid losses from diarrhea and/or vomiting

Healthy children can vomit or have loose stools once in a while without becoming dehydrated. But dehydration can occur suddenly and be very dangerous, especially for babies and young children. If children are vomiting, have watery stools, and are not able to drink, they can lose fluids quickly and become very sick.

Common signs and symptoms of dehydration

Your child may show one or more of the following symptoms of dehydration:

  • dry, cracked lips and a dry mouth
  • a decrease in urine output, no urine for 8 to 12 hours, or dark-coloured urine
  • drowsiness or irritability
  • cold or dry skin
  • low energy levels, seeming very weak or limp
  • no tears when crying
  • sunken eyes or sunken soft spot (fontanelle) on baby’s head 

Measuring dehydration

The Clinical Dehydration Scale is used by health care professionals to determine the severity of dehydration. You can use it as well. Using this scale can help to guide you as to whether your child is getting better, staying the same or getting worse. A doctor may use more findings to assess dehydration, but this scale is a good place to start.

The chart assigns points for certain signs or symptoms you observe in your child. The higher the point total, the worse the dehydration.

To calculate your child’s dehydration status:

  1. Mark down your child’s symptoms.

  2. For each symptom, find the point value in the chart.

  3. Add up the points and determine the score.

For example, if your child has dry mucous membranes (2 points), decreased tears (1 point), and a sweaty appearance (2 points), the total point value is 5 points. A score of 5 points means your child has moderate to severe dehydration.

Clinical Dehydration Scale





General appearance

Normal Thirsty, restless, or lethargic but irritable when touched Drowsy, limp, cold, sweaty


Normal Slightly sunken Very sunken

Mucous membranes*

Moist Sticky Dry


Present Decreased Absent

*Mucous membranes include the moist lining of the mouth and the eyes.

Score of 0 = no dehydration

Score of 1 to 4 = some dehydration

Score of 5 to 8 = moderate to severe dehydration

(Goldman 2008)

Treatment of dehydration

The treatment of dehydration is based on how dehydrated your child is. Over-the-counter medications to treat vomiting and diarrhea are not recommended for children.

Moderate to severe dehydration (score of 5 to 8 on the Clinical Dehydration Scale)

Take your child to see a doctor or go to the nearest hospital for assessment and treatment right away.

Mild dehydration (score of 1 to 4 on the Clinical Dehydration Scale)

Offer your child oral rehydration solution to replace the water and salts your child has lost. Commercially available oral rehydration solutions such as Pedialyte, Gastrolyte, Enfalyte or other brands contain a properly balanced amount of water, sugars, and salts to promote absorption of the fluid. It is best to use these products, rather than plain water or home-made solutions, especially for babies and young children. If your child refuses to take an oral rehydration solution, then try giving fluids that you know your child likes, such as milk or water mixed with juice. If your child has a fever, diarrhea or is vomiting, milk and juice are reasonable choices. However, if your child has severe diarrhea, milk and juice may make it worse.

Give your child 5 to 10 mL (1 to 2 teaspoons) every 5 minutes. Slowly increase this amount to reach the amount your child will tolerate. If your baby is breastfeeding, continue to breastfeed. If your baby refuses to breastfeed, see a doctor immediately.

No dehydration (score of 0 on the Clinical Dehydration Scale)

Continue to offer your child fluids and an age-appropriate diet. If your child has vomiting or diarrhea, give 10 mL/kg of an oral rehydration solution for each diarrhea or vomiting episode. Continue to offer your child small frequent feedings.

Treatment after rehydration

Once your child is better hydrated, the next step is to work toward getting him back to what they normally eat. This can usually happen about 4 to 6 hours after the last episode of vomiting. Offer your child the usual foods and drinks he enjoys.

You do not need to give your child a restrictive diet such as BRAT (bananas, rice, applesauce, toast). However, avoid offering your child foods that have a high sugar or sweet content, fried or high-fat foods, and spicy foods until they have recovered.

Do not dilute your child’s formula or milk with water, oral rehydration solution, or any other fluid.

If your child has ongoing vomiting or diarrhea, give 10 mL/kg of an oral rehydration solution for each stool or vomiting episode. You can also offer him the usual foods and drinks they enjoy. Even if there is diarrhea, it is usually better to continue offering milk and other nutritious foods your child’s body needs to recover and to heal.