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Electrolyte solutions are used to replace water and salt lost from vomiting and diarrhoea. This article looks at the different products available and how they should be used.

What are rehydration fluids?

Rehydration fluids are electrolyte solutions or tablets that are used to replace fluids. Brands include Gastrolyte, Pedialyte, Plasmalyte, and Sustalyte.

Use: Replacing the body with water and salts lost from vomiting or diarrhoea

When vomiting and/or diarrhoea occur the body loses fluid and salts (e.g. potassium, chloride, and sodium). It is important that the body has the right balance of fluids and salts, and that it is the right pH (acid balance). If the body loses fluid and salts it can get dehydrated and this affects the right concentration of salts (electrolyte imbalance). This can be serious, especially with young children and babies, or with elderly people. Therefore, your doctor will usually recommend the use of a mixture called an "Electrolyte Replacement Fluid" or "Rehydration Fluid", that puts back into the body the salts and fluids missing.

These mixtures do not stop or prevent diarrhoea or vomiting, they are used only to replace the water and salts your body has lost. In most cases the diarrhoea or vomiting will only be for 24-48 hours before the "stomach bug" is gone. Sometimes your doctor may give you something else to stop the vomiting or diarrhoea.

These mixtures contain a special balance of glucose (a sugar), salts and water. The glucose helps the water and salts to go into the body from the intestine. Flat lemonade or fruit juice, or salt and sugar mixed into water can be harmful because they are not the right balance. The specially made products (e.g. Gastrolyte, Pedialyte and Plasmalyte) should be used instead.

Gastrolyte comes in different flavours - natural, fruit, orange and blackcurrant. Each sachet is mixed with drinking water, however for babies or toddlers it is better to use freshly boiled and cooled water. It is important to mix it exactly according to the package directions, and not to add anything else to the mixture, or use anything other than water to mix it with. The sachets are convenient to take travelling or keep at home.

Plasmalyte and Pedialyte are already mixed up in the right concentration.

The pack usually has a guide of how much to drink.


Check with the doctor first if you have kidney problems.

Side effects:

The stomach may be upset if a large quantity is taken all at once.

Patient information:

  • Follow the instructions on the label of the medicine or as directed by your doctor.
  • Do not add anything else to these solutions; do not mix with lemonade, other soft drinks or fruit juice. Follow the exact directions for making up sachets or tablets into solution.
  • Check the directions on the packet - usually once the bottle is opened or the powder is mixed the liquid will need to be kept in the refrigerator and will need to be thrown out after 24 or 48 hours.
  • The mixtures can taste a bit salty, some people like the taste more if they are refrigerated.
  • Sip small amounts frequently.
  • For breastfed babies continue breastfeeding, and use the fluid replacement mixtures.
  • Babies with diarrhoea or vomiting should always be seen by a doctor.
  • If you have kidney problems, check with your doctor first.
  • You can get these mixtures on prescription from the doctor or you can buy them from a pharmacy.

If you have vomiting or diarrhoea the following tips may be useful:

  • Avoid alcohol and caffeine.
  • When you start to eat again don't have rich food (e.g. cream, fats) heavy meals, or milk first as these can upset the stomach more. Plain foods such as toast can be eaten, and gradually return to what you normally eat as your stomach comes right.
  • Always wash the hands well after using the toilet and before handling food to ensure no one else is infected.
  • See a doctor if the diarrhoea continues for a few days, if there is a high fever, if there is any blood in the stools (poo), if more than 5% of the body weight is lost, if the stomach feels very tender, there is a rash, or if there are any other symptoms other than the diarrhoea.
  • Home remedies such as flat lemonade can do more harm than good and are better avoided.

See also:

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