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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 mildly dehydrated children, half-strength apple juice and then whatever the child would drink beat an electrolyte solution, 16.7% against 25.0% treatment failure: what a child will swallow matters as much as the formula.4
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.10
| Drink | Sodium per 200 ml | Sugar per 200 ml | What it is | Use it for |
|---|---|---|---|---|
| Pharmacy oral rehydration sachet | About 300 mg | 3.6 g glucose | Medicine-category product; glucose, sodium, potassium and citrate in fixed ratio | Diarrhoea and vomiting with signs of dehydration |
| Electrolyte sachet or tablet | Roughly 100 to 500 mg; high-sodium sports sachets about 780 mg (1,957 mg in 500 ml) | Often none | A food supplement | Hot days, heavy sweating, low-intake days, recovery after a bug |
| Sports drink | About 90 to 230 mg | 12 to 16 g | A food; the register's "carbohydrate-electrolyte solution" | Exercise lasting over about an hour |
| Half-strength apple juice | Almost none | About 10 g | A drink, trialled in mildly dehydrated under-fives | A mildly dehydrated child who refuses a sachet |
| Flat cola | Almost none | About 21 g | A soft drink | Not a rehydration drink |
| Water and diluted squash | None | Little or none | The NHS first line | Everyone, in small sips |
Why does glucose matter in a rehydration drink?
Because the small intestine carries glucose and sodium across its wall together, water follows the sodium, and that transporter keeps working through most diarrhoeal illness, so a sugar-and-salt solution rehydrates when water alone passes straight through. The World Health Organization's formula since 2002 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, chosen after a Cochrane review found children on it vomited less and fewer needed a drip than on the stronger 1970s formula.5 Too much sugar draws water into the gut, the problem with undiluted juice and cola; 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 "Mainly potassium is lost", a forum line, is wrong: the main losses are water and sodium; potassium goes too, which is why the formula includes it, but 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 A pharmacist can recommend a sachet for a child, with medical supervision under two; over five, signs of dehydration mean the pharmacist for sachets and 111 if they persist.2 Parents' method matches the guidance: 5 ml by syringe every five to ten minutes, logged, which a child who vomits a cupful often keeps down; the solution frozen into lollies when refused; wet nappies as the test. The Canadian trial is the footnote: minimally dehydrated children did better on half-strength apple juice and then their preferred drinks, largely because they drank more.4 It is not a licence for juice and the NHS advice stands; a drink a child will swallow beats one they spit out, so try flavoured sachets first. 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 Chill it, make it to the stated volume and sip it over an hour. Once vomiting has stopped, milk is a good choice: a litre of rehydration solution or milk left about 300 g less urine over four hours than a litre of water, and milk kept exercise-dehydrated adults in fluid balance where water and a sports drink did not.7, 8 Salt water, rock salt and salted sugary drinks have no measured ratio and no trial behind them. An electrolyte sachet is a food whose place is the recovery days, once fluids stay down and appetite is still low; it is a food supplement, not an oral rehydration solution, and is not for treating gastroenteritis.
Is flat cola a rehydration drink?
No. A 200 ml glass carries about 21 g of sugar and almost no sodium, far more concentrated than body fluid, and in the beverage trial cola was no better than water at keeping fluid in the body.7 Letting it go flat removes the gas, not the sugar. For an adult who can keep nothing else down it is at least fluid; follow it with something containing sodium. For children the NHS is unambiguous: no fizzy drinks and no fruit juice during a bout.3 A pinch of salt does not make it a rehydration solution, since nobody knows the ratio; homemade mixes are not recommended for children.
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 People on a GLP-1 medicine have a leaflet instruction to avoid fluid depletion and electrolyte disturbances because dehydration can harm the kidneys; do you need electrolytes on Mounjaro works through that case. Older adults dehydrate more easily and feel it less; 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
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. 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; the kidneys need water to pass surplus sodium, so you cannot "flush" electrolytes out.
Which foods help firm up loose stools?
None stops diarrhoea; the NHS says eat when you feel able and avoid fatty or spicy food.2 Rice, potatoes, toast and bananas are easiest to tolerate; fruit juice, orange included, is best avoided during a bout.
Why are my stools never solid any more?
Diarrhoea beyond seven days, or a lasting change in bowel habit, is a GP appointment; the NHS lists medicines, food intolerance, coeliac disease, IBS and inflammatory bowel disease among the causes.2
Sources
- Product information for the UK pharmacy oral rehydration sachet (composition, cautions and age limits), on the MHRA products database. products.mhra.gov.uk.
- NHS. Diarrhoea and vomiting. nhs.uk/symptoms/diarrhoea-and-vomiting.
- NHS. Dehydration. nhs.uk/conditions/dehydration.
- Freedman SB, et al. Dilute apple juice and preferred fluids vs electrolyte maintenance solution in children with mild gastroenteritis. JAMA, 2016. PubMed 27131100.
- Hahn S, Kim Y, Garner P. Reduced osmolarity oral rehydration solution for treating dehydration due to diarrhoea in children. Cochrane Database of Systematic Reviews, 2002. PubMed 11869639.
- 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. PubMed 8897383.
- Maughan RJ, et al. A randomized trial to assess the potential of different beverages to affect hydration status. American Journal of Clinical Nutrition, 2016. PubMed 26702122.
- Shirreffs SM, Watson P, Maughan RJ. Milk as an effective post-exercise rehydration drink. British Journal of Nutrition, 2007. PubMed 17459189.
- Sarnowski A, et al. Hyperkalemia in chronic kidney disease: links, risks and management. International Journal of Nephrology and Renovascular Disease, 2022. PubMed 35942480.
- Department of Health and Social Care. Great Britain nutrition and health claims register. gov.uk.
This article is general information, not medical advice. Rehydration sachets are medicines: follow the pack, ask a pharmacist if you have kidney disease or diabetes, and seek advice before giving one to a child under two. Call 111 if fluids will not stay down.
