Oral Rehydration Sachets vs Electrolyte Drinks: What to Use When Ill

A pharmacy oral rehydration sachet and an electrolyte drink are different products. An oral rehydration solution (ORS) is a medicine-category product that pairs glucose with sodium in a set ratio, about 300 mg of sodium and 3.6 g of glucose in 200 ml for the UK pharmacy sachet, because the gut absorbs sodium and water fastest alongside glucose.¹ An electrolyte drink is a food, often sugar-free, with no glucose in that ratio. For a stomach bug the NHS order is water and diluted squash in small sips, a pharmacy sachet if there are signs of dehydration, and 111 if fluids will not stay down.^{2, 3} In 647 children with mild gastroenteritis and minimal dehydration, half-strength apple juice and then whatever the child would drink beat an electrolyte solution, 16.7% against 25.0% treatment failure.⁴

Sources checked on 30 October 2026.

Is an electrolyte sachet the same as a rehydration sachet?

No, and the label says which is which: a rehydration sachet lists glucose near the top, is labelled for fluid and electrolyte loss in diarrhoea and carries a dilution volume you must not vary; an electrolyte sachet lists sodium, potassium and magnesium, is usually sugar-free and is a food supplement, explained in the Wellgard electrolytes guide. The table compares them at the volume of one pharmacy sachet; sports-drink figures follow the GB claims register, juice and cola the UK composition tables.^{1, 10, 12}

Why does glucose matter in a rehydration drink?

The small intestine carries glucose and sodium across its wall together and water follows the sodium, so an oral rehydration solution rehydrates when water alone passes straight through. The reduced-strength formula trialled against the older World Health Organization solution is 75 mmol of sodium and 75 mmol of glucose per litre with 20 mmol of potassium, 65 of chloride and 10 of citrate, 245 mOsm per litre; in a Cochrane review of children in hospital it meant fewer unplanned drips and less vomiting than the older, stronger formula.^{5, 11} Fruit juice and fizzy drinks can make diarrhoea worse;² too little sodium replaces water but not salt, and in men dehydrated by exercise a drink with 61 mmol of sodium per litre was retained better than one with 23.⁶ A potassium-rich drink such as coconut water is not a rehydration solution (which drinks contain electrolytes has the figures).

What should you give a baby or child with a stomach bug?

Under 12 months, carry on breast or bottle feeding, smaller feeds more often if they are sick, formula at its usual strength, small sips of water between feeds for babies on formula or solids; call 111 if you are worried about a baby under 12 months, or if any child stops feeding.² From one to five: water or diluted squash in small sips, no fruit juice or fizzy drinks (both can worsen diarrhoea), and 111 for signs of dehydration: fewer wet nappies, drowsiness or irritability, a dry mouth, few or no tears, a sunken soft spot.³ Under two, the sachet is used only with medical supervision; over five, signs of dehydration mean the pharmacist for sachets and 111 if they persist.^{1, 2} The Canadian trial covered only children with minimal dehydration and is not a licence for juice; the NHS advice stands.⁴ Children under 12 are not given medicines to stop diarrhoea.²

What should an adult drink with a stomach bug?

Water and diluted squash in small, frequent sips; most adults need nothing else, and diarrhoea usually settles within five to seven days, vomiting within one or two.² Rehydration sachets are for signs of dehydration (dark urine, passing less than usual, dizziness, a dry mouth), and older people, anyone with a weakened immune system or a condition that raises their risk should see a pharmacist rather than wait.^{2, 3} Make it up with exactly 200 ml of water: a weaker or stronger mix upsets the balance.¹ Once vomiting has stopped, milk is a good choice: in a trial of 72 men funded by a hydration research institute, a litre of rehydration solution or milk left about 300 g less urine over four hours than a litre of water, and in a dairy-industry-funded trial milk kept 11 exercise-dehydrated adults in fluid balance where water and a sports drink did not.^{7, 8} An electrolyte sachet is a food supplement for the recovery days once fluids stay down, not an oral rehydration solution.

Is flat cola a rehydration drink?

No. A 200 ml glass carries about 22 g of sugar and almost no sodium, and in the beverage trial cola was no better than water at keeping fluid in the body.^{7, 12} Letting it go flat removes the gas, not the sugar. The NHS says fizzy drinks and fruit juice can make diarrhoea worse.^{2, 3}

Who should not self-treat with rehydration sachets?

The sachet's product information lists kidney disease, diabetes (the sachet is glucose) and low-sodium or low-potassium diets as reasons to take medical advice first.¹ Potassium is the quiet issue: in chronic kidney disease a high level is common and can be dangerous, and ACE inhibitors (ramipril), ARBs (losartan), spironolactone and amiloride raise it, so anyone on those asks a pharmacist first.⁹ The tirzepatide product information tells prescribers to advise patients to avoid fluid depletion and electrolyte disturbances because dehydration can harm the kidneys;¹³ do you need electrolytes on Mounjaro works through that case. Older adults are at higher risk; the NHS asks carers to offer drinks at mealtimes and watery foods like soup and jelly.³

When should you call 111 or 999?

Call 111 if you or your child cannot keep fluid down, if there is blood in the stool, if diarrhoea lasts more than seven days or vomiting more than two, if a child under five has signs of dehydration, if anyone five or over still has them after sachets, or any worry about a baby under 12 months; and for the NHS's urgent dehydration signs: feeling unusually tired (or a child who seems drowsy), dizziness on standing that does not go away, dark yellow urine or passing less than normal, and breathing quickly or a fast heart rate.^{2, 3} Call 999 for blood-stained or coffee-ground vomit, green vomit (yellow-green in a child), a stiff neck with pain in bright light, a sudden severe headache or stomach pain, blue, grey, pale or blotchy skin or lips, severe difficulty breathing, confusion, or sleepier than normal or difficult to wake; do not drive yourself.^{2, 3}

What we don't know

• Whether the apple-juice result holds for sicker children: the trial enrolled only children with mild illness and minimal dehydration.⁴
• Whether a sugar-free electrolyte sachet speeds recovery after a stomach bug: no trial has tested one in illness; the milk and rehydration-solution results come from healthy men.^{7, 8}

Frequently asked questions

Should I drink electrolytes if I have diarrhoea?

Water or squash in small sips first; with signs of dehydration, a pharmacy rehydration sachet. A sugar-free electrolyte sachet is a food for the recovery days; do you need to drink electrolytes every day covers daily use.²

What is the fastest way to replenish electrolytes?

During illness, a correctly made rehydration solution sipped steadily; otherwise a salted meal, a glass of milk and tap water.^{1, 7} An imbalance on a blood test is a doctor's job, never a sachet's; signs you need electrolytes explains the test.

Do I still need to drink water if I drink electrolytes?

Yes. An electrolyte drink is part of your fluid, not a substitute for it.

Which foods help firm up loose stools?

None stops diarrhoea; the NHS says eat when you feel able, that avoiding fatty or spicy food may help, and that fruit juice can make diarrhoea worse.²

Why are my stools never solid any more?

Diarrhoea for more than seven days is a call to 111; the NHS lists medicines, food intolerance, coeliac disease, IBS and inflammatory bowel disease among the causes.²

Sources

1. Oral rehydration salts sachet (glucose, sodium chloride, potassium chloride, disodium hydrogen citrate). Summary of Product Characteristics, sections 2, 4.2 and 4.4. Date of revision 30 June 2023. medicines.org.uk.
2. NHS. Diarrhoea and vomiting. Page last reviewed 21 December 2023. nhs.uk/symptoms/diarrhoea-and-vomiting.
3. NHS. Dehydration. Page last reviewed 1 May 2026. nhs.uk/conditions/dehydration.
4. Freedman SB, et al. Dilute apple juice and preferred fluids vs electrolyte maintenance solution in children with mild gastroenteritis. JAMA, 2016. Randomised single-blind trial, 647 children aged 6 to 60 months; non-government funding listed on PubMed. PubMed 27131100.
5. Hahn S, Kim S, Garner P. Reduced osmolarity oral rehydration solution for treating dehydration caused by acute diarrhoea in children. Cochrane Database of Systematic Reviews, 2002. Systematic review of randomised trials, 8 pooled for the main outcome; funding not stated on PubMed. PubMed 11869639.
6. Shirreffs SM, et al. Post-exercise rehydration in man: effects of volume consumed and drink sodium content. Medicine and Science in Sports and Exercise, 1996. Randomised trial, 12 men in two groups of six; funding not stated on PubMed. PubMed 8897383.
7. Maughan RJ, et al. American Journal of Clinical Nutrition, 2016. Randomised crossover trial, 72 men, 4 hours per drink; funded by a hydration research institute whose advisory board the lead author chaired. PubMed 26702122.
8. Shirreffs SM, et al. British Journal of Nutrition, 2007. Crossover trial, 11 people, four drinks; dairy-industry-funded. PubMed 17459189.
9. Sarnowski A, et al. Hyperkalemia in chronic kidney disease: links, risks and management. International Journal of Nephrology and Renovascular Disease, 2022. Narrative review; one author declares pharmaceutical grants and honoraria. PubMed 35942480.
10. Department of Health and Social Care. Great Britain nutrition and health claims register. Updated 19 May 2026. gov.uk.
11. CHOICE Study Group. Reduced osmolarity oral rehydration salts solution in children with acute watery diarrhoea. Pediatrics, 2001. Randomised double-blind trial, 675 children in five countries; non-government funding listed on PubMed. PubMed 11335732.
12. Public Health England. Composition of Foods Integrated Dataset (CoFID) 2021. Food composition dataset. gov.uk.
13. Mounjaro KwikPen, Summary of Product Characteristics, section 4.4. Date of revision 29 August 2026. medicines.org.uk.

Spotted something out of date? Email support@wellgard.co.uk with the page address and the sentence.

This article is general information, not medical advice. Rehydration sachets are medicines: follow the pack, and ask a pharmacist if you have kidney disease or diabetes.