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Oral rehydration therapy

Oral rehydration therapy (ORT) is a treatment for dehydration. It involves drinking a special mixture of water, glucose and salts to return the amount of fluids, sugars and electrolytes in the body to normal levels.

When is oral rehydration therapy needed for dehydration?

Most cases of dehydration are very minor and do not require any medical attention. They can usually be treated by drinking fluids such as water, breast milk, baby formula or diluted juices.

Oral rehydration therapy is used for treating the more serious dehydration that is caused by viral gastroenteritis, also known as stomach flu. This virus can cause a child to vomit repeatedly or have prolonged diarrhea, which can result in loss of fluids.

Around the world, viral gastroenteritis causes about 1.5 to 2.5 million deaths a year. In the United States and Canada, the dehydration that results from gastroenteritis results in about 220,000 hospital admissions a year. Most hospitalizations occur when dehydration is not treated early.

Benefits of oral rehydration therapy

If your child becomes severely dehydrated, they may need to have their fluids replaced through an intravenous line (IV). However, oral rehydration therapy is as effective as, if not better than, intravenous fluid therapy for rehydrating mild or moderately dehydrated children.

There are a number of reasons for this.

  • ORT is less traumatic for a child, as they will not need needle “pokes” for the IV or blood work.
  • ORT is easier to give in a range of settings, including at home.

What is in a typical oral rehydration solution?

An oral rehydration solution (ORS) is a specially-created solution that contains a mixture of:

  • water
  • glucose
  • sodium, potassium and other electrolytes.

Together, these ingredients help replace lost fluids and nutrients that the body needs to work properly. The solution normally takes about five minutes to start passing from the digestive system into the blood stream.

Where to get oral rehydration solution

Oral rehydration solution is sold at most pharmacies in:

  • pre-mixed bottles
  • packaged powders that need to be mixed with water.

Examples of commercial brands of ORSs include Pedialyte, Infalyte and Resol.

Pre-mixed liquid ORSs have the correct balance of fluids, salts and glucose. ORS powders are cheaper and have a longer shelf life. However, if a powder is not mixed with the exact amount of water specified, the resulting solution can either be too concentrated or too diluted, making it less effective.

Whether you use a pre-mixed bottle or packaged powder, follow the dosage directions exactly to maximize the effectiveness of the ORS.

How to give oral rehydration solution to your child

Give your child oral rehydration solution in small, frequent amounts. Use a spoon or dropper to make sure the first doses are very small. Small amounts will allow your child to better retain the ORS and reduce the chance of vomiting from the extra fluid in their system.

Gradually increase the amount of ORS until your child is able to drink the full dose recommended for them.

If your child refuses to drink the ORS, squirting the solution into their mouth with a syringe can be helpful.

In very rare cases, where a child refuses to drink the ORS by any of these measures, a nasogastric feeding tube​ can be used in hospital.

Can I use anything else to treat viral gastroenteritis?

Anti-emetic drugs (drugs used to treat nausea and vomiting) and probiotics can be useful when treating viral gastroenteritis.

Ondansetron is an anti-nausea drug that is relatively safe and has a low risk of negative side effects. Giving your child ondansetron will lower the risk of vomiting, which will help ensure that your child keeps down the ORS. Ondansetron is available by prescription from your doctor.

Probiotics are micro-organisms that help boost the body's immune system. Some probiotics may help children with viral gastroenteritis by reducing the duration of diarrhea. Probiotics can be found in foods such as yogurt and can also be bought at most pharmacies.

If I do not have an oral rehydration solution at home, can I give my child water or other drinks instead?

If your child has viral gastroenteritis, do not provide them with water on its own or with juices, fizzy drinks or sports drinks.

  • Drinking water alone can lead to low salt and sugar levels.
  • Juices, fizzy drinks and sports drinks contain high levels of glucose and low levels of electrolytes. They can cause diarrhea if they are given in large quantities.

Re-introducing food to a child after gastroenteritis 

As soon as your child has been rehydrated, you can start early refeeding. This involves re-introducing age-appropriate foods, which promotes better nutrition and reduces the duration of diarrhea.

If a breast-fed infant is dehydrated, continue breastfeeding throughout the illness. In non-breastfed infants, offer undiluted formula. The formula does not need to be lactose free.

When to get medical attention for dehydration

Go to the nearest emergency room if your child:
  • has not passed urine in more than 12 hours
  • is unusually sleepy or cranky
  • refuses to drink and continues to have diarrhea or vomiting
  • continues to drink but vomits and cannot keep anything down.

Key points

  • Oral rehydration therapy (ORT) is an effective form of treatment for dehydration caused by gastroenteritis.
  • ORT is an effective alternative to intravenous therapy and can be given in a range of settings.
  • Oral rehydration solution (ORS) can be bought in stores in a pre-mixed bottle or packaged powder.
  • ORS should be given in small, frequent amounts.
  • If your child’s dehydration or sickness does not improve with ORT, take them to the hospital for treatment.
​Shawna Silver, MD, FRCPC, FAAP, PEng

Canadian Paediatric Society (2006). Oral rehydration therapy and early refeeding in the management of childhood gastroenteritis​. Paediatr Child Health 2006;11(8):527-31.

Canadian Paediatric Society (2011; re-affirmed 2014). Emergency department use of oral ondansetron for acute gastroenteritis-related vomiting in infants and childrenPaediatr Child Health 2011;16(3):177-9.