Powders and tablets supplying sodium, potassium, magnesium and often chloride and glucose, dissolved in water for hydration during exercise, illness or heat exposure. Formulations range from medical oral rehydration salts to sports products with very different mineral ratios.
The evidence here splits sharply by product and purpose. WHO-formulation oral rehydration salts, with their specific glucose-to-sodium ratio, are one of the most effective public health interventions ever devised for diarrhoeal illness — that is not in dispute. Sports electrolyte products are a different proposition: for most exercise under an hour, water and ordinary food replace what is lost, and the trials showing performance benefit involve prolonged endurance exercise, heat, or high sweat rates. The important safety point runs opposite to the marketing: the dangerous electrolyte problem in endurance events is exercise-associated hyponatraemia from drinking too much fluid, which has killed marathon runners, and no commercial electrolyte drink reliably protects against it.
WHO-formulation ORS specifies 75 mmol/L sodium and 75 mmol/L glucose; sports products vary widely — a product without this marker may not resemble what was studied.
Regulation: Oral rehydration salts to the WHO formulation are a medicine in most countries; sports electrolyte products are foods or supplements with no pre-market review. No Tolerable Upper Intake Level has been set for potassium in healthy adults, and the sodium reference point is the 2,300 mg/day chronic disease risk reduction intake rather than an upper limit. Sodium and potassium content varies by an order of magnitude between products, and the 99 mg per-tablet limit on over-the-counter potassium does not apply to powdered drink formats.
What the research used
The amounts, forms and durations published trials of Electrolyte blends actually administered.
These are the amounts published trials administered — not a recommendation, and not a dose to copy. Trial participants were screened, supervised and given a characterised preparation. What is in a retail bottle is frequently not what was studied, and the amount that suits one person is not general advice.
Studied for WHO oral rehydration salts for diarrhoeal illness
75 mmol/L sodium
Strong
Reduced-osmolarity ORS, sipped continuously
The reduced-osmolarity formulation reduced vomiting, stool output and the need for intravenous fluids compared with the earlier formula. This is the medical use, and it is well evidenced.
Studied for Endurance exercise
300–600 mg sodium per hour
Moderate
Sports drink or powder in fluid
Sports nutrition guidance suggests sodium replacement during exercise beyond roughly 2 hours or in heat, particularly for salty sweaters. Individual sweat sodium losses vary several-fold, so a single figure fits few people.
Studied for Typical retail sachet
200–1000 mg sodium
Not enough
Per serving, with wide variation. Products aimed at low-carbohydrate diets can supply 1,000 mg or more of sodium per sachet, which matters for anyone managing blood pressure.
This is general information about food, not medical advice. It cannot diagnose, treat or replace guidance from a clinician who knows your history.
When it was taken
Each window says whether a trial compared it against an alternative, or whether it is convention and pharmacology. Most timing advice is the second kind.
Each timing below was actually compared against an alternative in a trial, which is unusual.
🏃Before exercise
Limited
Drinking a sodium-containing fluid before prolonged exercise in heat expands plasma volume modestly, which has been measured in laboratory studies of pre-exercise hyperhydration.
Timing was tested. A trial compared this window against another and reported a difference.
🕐Any time
Moderate
For illness, sipping continuously rather than drinking large volumes at once reduces vomiting — a well-established clinical practice from rehydration research.
Timing was tested. A trial compared this window against another and reported a difference.
The evidence in depth
Best supported: Moderate
What each association actually rests on, and the papers behind it. A rating describes the state of the research, not how promising the supplement sounds. How we rate evidence.
Fluid and sodium replacement supports performance during prolonged exercise, in heat, or where sweat losses are high — the trials that show benefit are in those conditions. For typical exercise under an hour, water and ordinary meals are sufficient and electrolyte products have not been shown to add anything.
What may be going on: Sodium maintains plasma volume and drives thirst and fluid retention; carbohydrate co-transport increases intestinal water absorption, which is the basis of the oral rehydration formula.
Moderate evidence. Several human studies point the same way, with real caveats.
Sodium-containing fluids restore plasma volume after dehydrating exercise more effectively than water alone, which is measurable. The popular claim that electrolytes reduce muscle cramp is much weaker — cramp research points more toward neuromuscular fatigue than electrolyte loss.
Limited evidence. Early human work, or mostly lab and animal research.
Oral rehydration salts to the WHO formulation reduce the need for intravenous fluids and shorten illness in diarrhoeal disease, with reduced-osmolarity solutions performing better than the original formula. That evidence belongs to the specific medical formulation, not to sports powders.
Not enough evidence. Not enough human research to say anything useful yet.
No source is attached to this association yet, so it is rated not enough evidenceby default. It is listed because people commonly ask about it — not because there is evidence for it.
Things to know
Interactions, contraindications and dose limits, most serious first. Concentrated extracts interact with medication in ways the whole plant does not, so this section carries more weight here than it does on a food page.
Too much
Hyponatraemia comes from too much fluid, not too little salt
Exercise-associated hyponatraemia — dangerously low blood sodium from drinking more fluid than is lost — has caused deaths in marathons and military training. Electrolyte drinks do not reliably protect against it, because the problem is fluid volume. Drinking to thirst rather than to a schedule is the guidance that follows from the research.
Worth knowing
Sodium load matters for blood pressure and kidney disease
Some products supply 1,000 mg or more of sodium per serving, and several a day approaches or exceeds a whole day's recommended intake. That matters for anyone with hypertension, heart failure or kidney disease.
Interaction
Potassium content interacts with common heart and blood pressure drugs
Potassium in electrolyte powders adds to the effect of ACE inhibitors, angiotensin receptor blockers, potassium-sparing diuretics and NSAIDs, all of which raise blood potassium. In kidney impairment this combination can become dangerous.
Worth knowing
Sports formulations are not rehydration solutions
For diarrhoeal illness, particularly in children, sports drinks have the wrong sodium and sugar composition and can worsen diarrhoea osmotically. The medical formulation exists for a reason and is inexpensive.
Worth knowing
Added sugar and sweeteners
Products range from sugar-free to 20 g or more of sugar per serving. Carbohydrate is functional during prolonged exercise and is simply added sugar the rest of the time.
In the food catalogue
The whole-food form, where one exists. The evidence for a concentrated extract rarely transfers to the food, or the other way round — these are cross-links, not equivalents.