Rehydration salts

Also called oral rehydration solution or ORS

Rehydration salts are used to replace salts and water that the body loses when you have dehydration. Find out how to take it safely and possible side effects.

Type of medicine Also called
  • Used to replace fluids and electrolytes
  • Pedialyte®
  • Electral®
  • Gastrolyte®
  • Enerlyte®
  • Hydralyte®

What are oral rehydration salts?

  • Oral rehydration salts (ORS) are a mixture of electrolytes (salts), and carbohydrates (in the form of sugar), which are dissolved in water. They are used to replace salts and water that the body loses when you have dehydration caused by gastroenteritis, diarrhoea, or vomiting.
  • Unlike other fluids, the proportion of salts and sugar in an ORS matches what the body needs to recover.
  • Fizzy drinks, undiluted juices, tea, coffee and sports drinks are not suitable because of their high sugar content. High sugar content is likely to make diarrhoea worse. 
  • Commercially-available ORS products can be bought from pharmacies and are often available in different flavours.     
  • Home-made salt/sugar mixtures are used in developing countries if rehydration drinks are not available but they have to be made carefully, as too much salt can be dangerous for children. 


The usual dose of oral rehydration salts depends on age. The following is a guide:

  • child 1 month to 1 year: 1–1½ times usual feed volume.
  • child 1 to 12 years: 200 mL (~1 cup) after every loose bowel motion.
  • child 12 years and over and adults: 200 to 400 mL (~1 to 2 cups) after every loose bowel motion.

Your health provider will tell you how much ORS to take, how often to take it and any special instructions.

How to prepare oral rehydration salts

  • Commercially-available oral rehydration salts may be available as a solution already mixed in water or may be bought as sachets that will require mixing with water.
  • Follow the instructions on the packaging, for preparing the ORS.
  • Always use boiled water to prepare the ORS.
  • Some brands of ORS (such as Pedialyte) must be used within 1 hour of mixing. Any unused solution should be discarded unless stored in a refrigerator where it may be kept for up to 24 hours.
  • Do not boil the ORS solution after mixing.

How to take oral rehydration salts

If you (or your child) are unable to drink the full dose needed, all at one go, try drinking it in small sips over a longer time period. It may help to use a straw or to chill the solution.

  • If your child is sick less than 30 minutes after drinking the oral rehydration salts, give them again.
  • If your child is sick more than 30 minutes after drinking the oral rehydration salts, you do not need to give them again until they have their next runny poo.
  • Oral rehydration salts should start working quickly and dehydration usually gets better within 3 to 4 hours.

You will not harm your child by giving too much of the oral rehydration salts, so if you are not sure how much your child has kept down because they are being sick, it is better to give more rather than less of the oral rehydration salts.

Other useful tips

  • You should not use oral rehydration salts to treat diarrhoea for more than 2 to 3 days unless your doctor has told you to.
  • You should only use water to mix with the oral rehydration salts; do not use milk or juice and never add extra sugar or salt. This is because the rehydration salts contain the right mix of water and salts to help the body best.
  • You must be careful to use the right amount of water to make up the medicine, as too much or too little can mean the salts in your child’s body are not properly balanced.
  • Oral rehydration salts are safe and do not usually have side effects. 

Learn more

The following links provide further information on oral rehydration salts.

Oral rehydration salts Medicines for Children, UK


  1. Assessment and management of infectious gastroenteritis BPAC December 2009
  2. Oral rehydration salts New Zealand Formulary
Credits: Editorial team. Last reviewed: 10 Aug 2016