Oral Rehydration Solution for Diarrhoea: How and When to Use It

Quick answer

Oral rehydration solution (often shortened to ORS) is a powder of measured salts and sugar that you dissolve in water and drink. It replaces the fluid and minerals your body loses through diarrhoea and vomiting, and it is the main way to prevent and treat dehydration at home. Common pharmacy brands come as sachets.

ORS does not stop diarrhoea. Its job is to keep you hydrated while a stomach bug runs its course, which matters most for babies, young children, older adults and people with long-term health conditions. Many healthy adults with a mild bug can stay hydrated with water and other drinks, but ORS is the better choice once you are being sick repeatedly, have frequent watery stools, or start to show signs of dehydration.

What the research says

ORS contains glucose and electrolytes (body salts) in set amounts. The World Health Organization and UNICEF have long promoted it as a cornerstone of diarrhoea care, and in a joint statement they described a newer formula with lower concentrations of glucose and salt as one of the important advances in managing diarrhoeal disease, alongside zinc supplements for children with diarrhoea.

The evidence for that newer formula comes partly from a Cochrane review (Hahn and colleagues, 2002) that compared "reduced osmolarity" ORS with the older WHO standard solution in children admitted to hospital with diarrhoea. Pooling eight trials, the review found that children given the newer solution were less likely to need an unplanned drip of intravenous fluids (odds ratio 0.59). They also passed less stool and vomited less, and the review did not find a higher risk of low blood sodium.

Health services recommend ORS for use at home. The NHS recommends oral rehydration solutions from a pharmacist for anyone who is being sick or has diarrhoea and needs to replace lost sugar, salts and minerals. The US National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) lists ORS among the drinks that replace fluids and electrolytes in both adults and children.

The Cochrane trials were in children treated in hospital. For healthy adults with uncomplicated traveller's diarrhoea, the Government of Canada's travel health advice says diluted sports drinks, safe water, clear soups or diluted juices are usually enough, with ORS more strongly recommended for children, older adults and people with underlying conditions.

How to use it

Mixing a sachet

• Follow the instructions on the pack exactly. For one widely used UK brand, an NHS hospital leaflet says to empty one sachet into 200 ml of drinking water, using cooled boiled water for babies under one year.
• Use the correct amount of water. Too much or too little can upset the body's salt balance.
• Mix with water only. Do not add milk, juice, extra sugar or salt.
• Once made up, the same NHS leaflet advises using the drink within one hour at room temperature, or keeping it in the fridge for up to 24 hours. Storage times differ between products, so check your pack.

How much to drink

• Start drinking as soon as diarrhoea begins, aiming for pale urine.
• WHO amounts quoted by the Government of Canada are roughly 50 to 100 ml after each loose stool for children under two, 100 to 200 ml for children aged two to nine, and as much as wanted (up to about 2 litres a day) from age ten upwards. A pharmacy product's label or a doctor's advice takes priority.
• If you feel sick or are vomiting, take small sips. For children, the NHS leaflet suggests 10 to 20 ml every 5 to 10 minutes.
• If a child vomits within 30 minutes of a dose, the NHS leaflet advises giving that dose again.

Food and other drinks

• Keep breastfeeding or giving usual formula to babies. Do not make formula weaker.
• Eat when you feel able. Northern Ireland's official health advice (nidirect) says no specific foods need to be included or avoided.
• Avoid alcohol and caffeinated drinks, which can make dehydration worse. Fruit juice and fizzy drinks can make diarrhoea worse, and the NHS advises not giving them to young children.
• Homemade sugar-and-salt mixtures are easy to get wrong. Canadian travel advice does not recommend them for treating dehydration and suggests carrying commercial sachets instead.

Possible side effects and interactions

ORS rarely causes side effects when mixed correctly, according to NHS hospital guidance for parents. Mixing it correctly matters, because a solution made with too much or too little water can upset the body's balance of salts. An accidental extra dose is unlikely to cause harm.

The same leaflet says paracetamol and ibuprofen can be given alongside ORS unless a doctor has said not to. Anti-diarrhoea medicines such as loperamide can ease diarrhoea for a few hours in adults, but they are not suitable for young children. Check with a pharmacist before combining ORS with other remedies.

Who should be careful

• Kidney or liver disease: the NHS leaflet advises not using ORS unless a doctor has recommended it.
• Diabetes: ORS contains sugar, so ask your doctor or diabetes nurse for advice before using it.
• Older adults and people with weakened immunity: NIDDK advises talking with a doctor first, as a specific solution or amount may suit you better.
• Infants: speak to a doctor, health visitor or pharmacist before giving ORS to a baby, and continue milk feeds.
• Other long-term conditions or regular medicines: if you are unsure whether ORS suits you, ask a pharmacist which product is right for you, as the NHS suggests.

The NHS leaflet also says not to keep giving ORS for more than two or three days unless a doctor advises it.

When to see a doctor

Get urgent medical advice (a GP appointment, NHS 111 or your local equivalent) if there are signs of serious dehydration:

• unusual tiredness, or a child who is drowsy
• dizziness on standing that does not go away
• dark urine or passing very little urine, or fewer wet nappies in a baby
• fast breathing or a fast heartbeat
• few or no tears when a child cries, or a sunken soft spot on a baby's head

Adults should also see a doctor if diarrhoea lasts more than seven days or vomiting more than two days, if fluids will not stay down, if they are still dehydrated despite ORS, or if there is blood in the stool or green or yellow vomit. Pregnancy, age over 60, recent travel to an area with poor sanitation, and long-term conditions such as diabetes or kidney disease are also reasons to get checked sooner. High fever or yellowing of the skin with diarrhoea needs medical care too.

Call emergency services if someone has signs of dehydration together with pale, grey, blue or blotchy skin or lips, cold skin, difficulty breathing, confusion, or is very hard to wake. Vomiting blood, vomit that looks like coffee grounds, a sudden severe headache or stomach ache, or a stiff neck with pain when looking at light are also emergencies.

Frequently asked questions

Can I use a sports drink instead of oral rehydration solution?

For a healthy adult with mild diarrhoea, water, broth or a sports drink is often enough, and Canadian travel advice mentions diluted sports drinks for uncomplicated cases. Sports drinks are not made to the same recipe as ORS, though. For babies, young children, older adults or anyone showing signs of dehydration, a proper ORS is the safer choice.

How long does a stomach bug usually last?

In adults, vomiting usually settles in about two days, and diarrhoea lasting up to ten days is not unusual. In children, diarrhoea usually lasts five to seven days and vomiting one to two days. You are most infectious until two days after symptoms stop, so stay off work or school until then.

Can I make oral rehydration solution at home?

Homemade recipes exist, but small measuring mistakes can make the drink too salty or too weak. Canadian government travel advice says homemade versions are not recommended to treat dehydration and should only be a stopgap when sachets are not available. Keeping a few sachets in a first aid kit is a simple precaution.

References

• NHS: Dehydration
• nidirect (Northern Ireland government health information): Diarrhoea and vomiting (gastroenteritis)
• Hahn S, Kim Y, Garner P. Reduced osmolarity oral rehydration solution for treating dehydration caused by acute diarrhoea in children. Cochrane Database of Systematic Reviews, 2002
• NIDDK (US National Institutes of Health): Treatment of diarrhea
• Worcestershire Acute Hospitals NHS Trust: Oral rehydration salts (patient leaflet)
• Government of Canada: Oral rehydration solutions (travel health advice)