Gastrointestinal
Oral rehydration salts
Rehydration sachets (ORS) — Replace water and salts lost in diarrhoea and vomiting — the mainstay of treating dehydration.
Education and reference only. This is a plain-language class overview — it deliberately contains no doses. Always check the current Summary of Product Characteristics (SmPC), the BNF and your local formulary before prescribing or administering any medicine.
Quick answer
What is Oral rehydration salts?
Oral rehydration salts are sachets of balanced sugars and minerals dissolved in water to replace the fluid and salts lost through diarrhoea and vomiting. They are the main treatment for mild-to-moderate dehydration.
- How it works: The specific balance of glucose and sodium lets the gut absorb water efficiently even during a diarrhoeal illness — glucose and sodium are taken up together, pulling water in with them.
- In practice: In practice oral rehydration salts are the cornerstone of managing the dehydration of gastroenteritis, especially in children and older or frail people, and they work better than water alone because their carefully balanced mix of glucose and salts is absorbed efficiently even when the gut is inflamed.
What it is
Oral rehydration salts are sachets of balanced sugars and minerals dissolved in water to replace the fluid and salts lost through diarrhoea and vomiting. They are the main treatment for mild-to-moderate dehydration.
How it works
The specific balance of glucose and sodium lets the gut absorb water efficiently even during a diarrhoeal illness — glucose and sodium are taken up together, pulling water in with them. This replaces losses far more effectively than plain water.
In practice
In practice oral rehydration salts are the cornerstone of managing the dehydration of gastroenteritis, especially in children and older or frail people, and they work better than water alone because their carefully balanced mix of glucose and salts is absorbed efficiently even when the gut is inflamed. The sachets are dissolved in the correct volume of clean (in the UK, freshly boiled and cooled, or bottled) water — never made stronger — and sipped little and often, which is better tolerated than large amounts at once when someone feels sick. They replace losses but do not stop the diarrhoea, and the priority is maintaining hydration while the illness settles. Warning signs that need medical help include being unable to keep fluids down, signs of significant dehydration, blood in the stool, or a baby or frail person becoming drowsy or passing little urine.
Examples
Practical use
How to take it & use it well
- Make up the sachet with the exact amount of clean, cooled water stated on the pack. Do not make it stronger or weaker, as the balance of salts and sugar matters.
- Sip it slowly and often rather than drinking large amounts at once, especially if you are feeling sick, to help your body absorb the fluid.
- Use it to replace fluid lost through diarrhoea or vomiting. It rehydrates you but does not stop the diarrhoea itself.
- Once made up, use it within the time stated, keep it covered in the fridge if advised, and discard any leftover after that period.
- Continue your normal feeds or meals as you are able, and keep using the solution after each loose stool to keep up with losses.
- Use freshly boiled and cooled or bottled water if there is any doubt about water quality.
Common uses
- Dehydration from gastroenteritis (diarrhoea and vomiting)
- Maintaining hydration in vulnerable groups (children, elderly)
- High-output losses (e.g. from a stoma), under advice
Monitoring
- Hydration (urine output, alertness) and symptom course
- Ability to keep fluids down
- Red-flag features needing medical review
Weighing it up
Advantages & disadvantages
Advantages
- It replaces the water and salts lost during diarrhoea and vomiting, helping to prevent or treat dehydration.
- It is simple, inexpensive and available without prescription.
- The balanced mix of salts and sugar helps the gut absorb fluid more effectively than water alone.
- It is suitable for most ages, including children, when made up correctly.
- It can often keep people out of hospital by managing mild dehydration at home.
Disadvantages
- It does not cure the underlying infection or stop the diarrhoea, only replaces what is lost.
- Made up too strong, it can upset the body's salt balance, which is why exact mixing matters.
- Some people dislike the taste, which can make it hard to take enough.
- It is not enough on its own for severe dehydration, which needs urgent medical care.
- It must be made with clean water, which may be a concern when travelling.
Key safety principles
What to watch for
- Make up with the correct volume of clean water and do not make it stronger than directed.
- Sip little and often; it replaces fluid but does not stop the diarrhoea.
- Seek help if fluids cannot be kept down, there are signs of significant dehydration, blood in the stool, or drowsiness/reduced urine (especially in babies or frail people).
Key interactions
What to avoid or check alongside
- People with diabetes should monitor their blood sugar, as the solution contains sugar.
- Those on a restricted-salt diet or with kidney or heart conditions should check with a pharmacist or doctor before using it, because of the salt content.
- Mixing it with juice, fizzy drinks or extra sugar upsets the careful balance and can worsen diarrhoea.
- It should not delay seeking help for warning signs such as not passing urine, drowsiness, or blood in the stool.
Patient & carer advice
- Mix exactly as directed with clean water — not stronger
- Take small sips often rather than large drinks
- Keep going until the illness settles, and seek help for the warning signs
Answers
Oral rehydration salts: frequently asked questions
Does oral rehydration solution stop diarrhoea?
No, it does not stop diarrhoea or cure the infection causing it. It replaces the fluid and salts you lose, which prevents dehydration while your body recovers.
Can I make the solution stronger to work better?
No, always make it up with the exact amount of water stated. Making it too strong can disturb your body's salt balance and do more harm than good.
When should I get medical help instead?
Seek help if you cannot keep fluids down, become drowsy or confused, stop passing urine, or see blood in the stool. These can be signs of serious dehydration or illness.
Can children use oral rehydration salts?
Yes, they are commonly used for children with diarrhoea and vomiting when made up correctly. Offer small amounts often, and seek advice if a young child is not improving or shows signs of dehydration.
Can I use it if I have diabetes?
You can, but the solution contains sugar, so monitor your blood glucose more closely while using it. Ask your pharmacist or diabetes team if you are unsure.
Authoritative sources
Always verify against the source
This overview is for orientation. For doses, interactions, contra-indications and the full monograph, use:
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