Gastroenteritis factsheet


Gastroenteritis is also known as gastro. It is a very common illness in babies and children and is caused by viruses that infect the digestive system. Gastroenteritis causes cramps, vomiting and diarrhoea. It tends to be more common during winter months and spreads easily.

 Signs and symptoms

Gastroenteritis usually starts with vomiting. Children then develop frequent, watery poos called diarrhoea. Children may also have tummy pain and fever with the diarrhoea. Some children may also have a runny nose, or a sore throat.

See your local doctor or take your child to the nearest emergency department if they:

  • are less than six months old 
  • have other health problems
  • are unable to drink fluid without throwing it up
  • do not stop vomiting
  • are very tired or drowsy
  • have blood or mucus in their poo
  • have ongoing tummy pain
  • have high fevers
  • have unexpected symptoms like pain when doing a wee or headaches
  • does not seem to be getting better and you are worried.

If your child’s vomit becomes a green colour, call triple zero (000) for an ambulance or go to your nearest emergency department immediately.


Your child’s doctor will be able to make a diagnosis based on their symptoms.


Most children with gastroenteritis will recover quickly. The major concern with gastroenteritis is that children can become dehydrated as they lose fluids through vomiting and diarrhoea. Babies, younger children, and children with other health problems can become dehydrated more quickly. 

It is important to encourage your child to drink fluids, even if they are unwell and vomiting.

Medicines to stop vomiting can be used for children who are dehydrated from vomiting too much.

Medicines to stop diarrhoea are not recommended as they can cause other health problems in children.

Make sure to ask your doctor any questions you have about treating gastroenteritis.

Children with Gastroenteritis are infectious. It is important to wash your hands thoroughly before and after:

  • touching your child
  • feeding your child
  • changing your child’s nappy
  • cleaning up vomit and diarrhoea.

Keep your child away from other children as much as you can until the diarrhoea has stopped. Check with your school or day-care provider about their rules for gastroenteritis.



Vomiting and diarrhoea can cause your child to lose a lot of fluid from their body. Lost fluid must be replaced as soon as possible so they do not become dehydrated.

Oral Rehydration Fluids

Oral rehydration fluids can be bought from the chemist or supermarket. They are specially formulated to replace lost fluid, sugars, and salts (also known as electrolytes). Oral rehydration fluids are the best type of fluids to give.

Clear fluids

Clear fluids are fluids you can see through. They include water, some types of juice, cordial, and soft drinks like lemonade. Clear fluids can be given if an oral rehydration fluid is not available but must be watered down. Dilute clear fluids by using the recipes below.

Cordial concentrate (not low calorie/low joule) - 1 part cordial in 20 parts of water, e.g., 5 mL (1 teaspoon) plus 100 mL water

Soft drink or juice (not low calorie/low joule) - 1 part juice in 4 parts of water, e.g., 20 mL (1 tablespoon) plus 80 mL water

Amount of fluid to give your child

It is important to be patient when giving your child fluids. They will feel unwell and may not want to drink. It is important they replace their fluids by taking small sips, more frequently. You should offer your child a sip of fluid every time they vomit.

Aim to give at least 5mL of fluid per kg of body weight, every hour.

For example:

  • for a 6kg infant, offer 30mL every hour or 60mL every 2 hours
  • for a 12kg toddler, offer 60mL every hour or 120mL every 2 hours.

Approximate volumes for children aged:

  • less than 6 months – talk to your local doctor for advice
  • 6-23 months – 40 to 60 mL each hour
  • 2-5 years – 60 to 100 mL each hour
  • 6-10 years – 100 to 120 mL each hour
  • 11-16 years – 120 to 160 mL each hour.

If your child is keeping fluids down, you can gradually increase the amount they have per sip, while slowing down the frequency. You should keep the same volume of fluids overall.

It is important to give your child easily digested foods as soon as the vomiting stops, even if they are still experiencing diarrhoea. Do not let your child go over 24 hours without food.

Fluids for breastfed infants (over 6 months)

If your baby is breastfeeding, is over 6 months and has gastroenteritis, you should:

  • continue breast feeding or offering expressed milk on demand or at least every 2 hours
  • offer water or oral rehydration solution with a syringe, in between breast feeds
  • not give them solids while they are vomiting.

when the vomiting has stopped or after 24 hours, you can:

  • continue to breastfeed or offer expressed milk on demand, or every 2-3 hours
  • offer water or oral rehydration solution with a syringe, in between feeds
  • introduce simple foods like rice cereal, potato, or pumpkin if your infant is eating solids; even if their poo is still runny. 

If your baby is younger than 6 months, see your local doctor or present to your nearest emergency department as soon as possible.

Fluids for formula-fed infants and older children (over 6 months)

While your infant or child is still vomiting you should:

  • replace formula or usual drinks with oral rehydration fluid or suitable fluids for the first 12 hours
  • start to give normal formula or milk in smaller amounts more frequently.
  • continue to give feeds or drinks every 2-3 hours or more frequently if your child wants them
  • offer age-appropriate foods at mealtimes, even if your child is still having diarrhoea.

Do not dilute formula or milk.

Lactose intolerance

Occasionally children will develop lactose intolerance after gastroenteritis, and the diarrhoea will continue. Lactose intolerance is a sensitivity to the sugars found in milk that can cause a bad reaction in the gut. If this happens, take your child to their local doctor, and discuss any short-term dietary changes that may help.

When to see your doctor

Severe vomiting and diarrhoea can quickly lead to dehydration babies and children. See your local doctor or present to your nearest emergency department if you have any concerns about your child’s progress or think they are dehydrated.

Last updated Thursday 7th December 2023


This factsheet is provided for general information only. It does not constitute health advice and should not be used to diagnose or treat any health condition.

Please consult with your doctor or other health professional to make sure this information is right for you and/or your child.

The Sydney Children’s Hospitals Network does not accept responsibility for inaccuracies or omissions, the interpretation of the information, or for success or appropriateness of any treatment described in the factsheet.

© Sydney Children’s Hospitals Network 2024