How to Choose an Electrolyte Supplement: Reading the Label

No published human trial has compared electrolyte formats, tablet, effervescent tablet, powder, sachet, ready-to-drink, drop or gummy, at the amounts a serving holds, so none can be ranked. Compare what a serving delivers: sodium as the element in milligrams (1,000 mg of sodium chloride carries about 390 mg of sodium), potassium and magnesium against their claim lines, sugar, caffeine and servings a day. Water suits most days; a measured drink suits the days that cost salt. Part of the Wellgard electrolyte guide.

Evidence at a glance

• Trials: none compares formats at serving amounts; this page rests on sweat data from 506 athletes and trials of 12 men, 11 adults and 72 men.^{1, 2, 3, 4}
• Largest trial: 72 men, 13 drinks, urine over four hours.⁴
• Strongest measured outcome: median urine over 7.5 hours of 260 ml after a 61 mmol/L sodium drink against 493 ml after a 23 mmol/L drink (six men per drink).²
• Not tested: any format against another.

Sources checked on 13 October 2026.

What is a heavy-sweat formula for, and what is a low-sodium one for?

Labels tend to fall into two sizes: low-sodium formulas at about 200 to 500 mg of sodium a serving, for lighter days, and heavy-sweat formulas at about 1,000 to 2,000 mg, for an hour or more of hard sweating in an adult without a kidney or blood-pressure condition.

In 506 athletes, sweat sodium averaged 36 mmol/L, about 0.8 g a litre (range 18 to 71 mmol/L), at 1.2 litres an hour (range 0.26 to 5.73).¹ The NHS says "Adults should have no more than 6g of salt a day", 2.4 g of sodium, and an hour of hard sweating takes roughly a gram of sodium back out, a heavy, salty sweater several times that.^{5, 6, 1} Whether today needs one: do you need electrolytes every day; the weigh-yourself method: electrolytes for runners; timing: when to take electrolytes.

Sodium comes first because it decides how much of a drink you keep. After 12 men sweated off about 2% of body mass and drank that volume back, median urine over 7.5 hours was 260 ml with a 61 mmol/L sodium drink and 493 ml with a 23 mmol/L one.²

How do you read sodium on the label?

Find sodium in milligrams, not the salt it came from. By molecular weight, sodium chloride is about 39% sodium, sodium citrate about 23 to 27% and sodium bicarbonate about 27%. Supplements give sodium per tablet, sachet or dose; a ready-to-drink bottle gives salt per 100 ml, and salt divided by 2.5 is sodium.⁶ Per litre, 400 mg made up in 500 ml is 800 mg, about average sweat and inside the register's 460 to 1,150 mg band for sports drinks.^{1, 7}

Is sodium citrate bad for you? The stomach upsets reported with this sodium salt of citric acid come from sports research loading about 500 mg per kilogram of body weight, roughly 35 g for a 70 kg adult; a review of 33 such studies recorded gut symptoms at those loads, fewer when the dose was swallowed as capsules than drunk.⁸ A serving holds far less.

Potassium, magnesium and calcium: what do the label figures mean?

A label may make a mineral claim only where a serving gives 15% of the nutrient reference value (NRV): 300 mg of potassium (NRV 2,000 mg), 56.25 mg of magnesium (375 mg), 120 mg of calcium (800 mg).⁹ At those amounts, attributed to the nutrient: potassium contributes to normal muscle function, normal functioning of the nervous system and the maintenance of normal blood pressure; magnesium contributes to electrolyte balance; calcium contributes to normal muscle function.⁷ Sodium has no authorised claim.⁷

Read the element, not the compound: potassium chloride is about 52% potassium, potassium citrate 36 to 38%; magnesium citrate 11 to 16% magnesium, magnesium oxide about 60%; calcium carbonate 40% calcium. The NHS puts adult potassium needs at 3,500 mg a day, calls supplements of 3,700 mg of potassium a day or less "unlikely to have obvious harmful effects", and says "Taking high doses of magnesium (more than 400mg) for a short time can cause diarrhoea."⁶

Sugar, sweeteners and caffeine: what should you check?

The register's two hydration wordings, including "enhance the absorption of water during physical exercise", belong only to carbohydrate-electrolyte solutions meeting four conditions: 80 to 350 kcal a litre from carbohydrate; at least 75% of it from high-glycaemic sugars; 20 to 50 mmol/L of sodium; an osmolality of 200 to 330 mOsm/kg water.⁷ A sugar-free product sits outside that definition, so the wording is not used; it speaks through its minerals, such as magnesium and electrolyte balance.⁷

A food with a sweetener must say "with sweetener(s)" beside its name, and one with over 10% added polyols "excessive consumption may produce laxative effects".¹⁰ A drink above 150 mg of caffeine a litre carries a high-caffeine warning; a supplement with added caffeine says "Contains caffeine" with the amount per daily portion.¹⁰ The NHS says "Check the label for drinks that are high in caffeine", and no more than 200 mg a day in pregnancy.¹¹

Tablets, powders, drinks, drops and gummies: what does the format change?

Format changes dose, servings, water, taste and convenience; no published trial has compared formats at serving amounts.

Drinks compared: which drinks contain electrolytes.

Who should read the label most carefully?

With high blood pressure, heart failure or kidney disease, or a medicine that holds sodium or potassium, ask a pharmacist or GP before using any electrolyte product. In a Cochrane review of 195 trials, cutting sodium from about 203 to 65 mmol a day lowered systolic pressure in white participants by about 1 mmHg with normal blood pressure and nearly 6 mmHg with hypertension (high-quality evidence).¹² Across 32 trials, extra potassium raised blood pressure above a difference of about 80 mmol a day in people on blood-pressure drugs.¹³ High blood potassium is common in chronic kidney disease and with ACE inhibitors, angiotensin receptor blockers, spironolactone or amiloride.¹⁴ The NHS says "Older people should not take potassium supplements unless advised to by a doctor."⁶

Adult formulas are sized for adults; the NHS child salt maximum is 2 g a day at 1 to 3 years, and a child with dehydration signs is a pharmacist or 111 matter.^{5, 15} In pregnancy or breastfeeding the NHS says you may need more fluid.¹¹ Vomiting and diarrhoea are a pharmacy rehydration solution's job: rehydration sachets vs electrolyte drinks.

How do you compare two electrolyte products without a brand?

Read six lines.

1. Sodium in milligrams, per serving and per litre made up.
2. Potassium against 300 mg, magnesium against 56.25 mg, calcium against 120 mg.
3. Sugar in grams, or "with sweetener(s)".
4. Any caffeine statement.
5. Servings a day times sodium, against the NHS 2.4 g of sodium (6 g of salt) and the roughly 0.8 g each litre of sweat takes out.^{5, 1}
6. The printed cautions.

What we don't know

• No published human trial has compared electrolyte formats with one another at serving amounts.
• No trial has set different electrolyte amounts for women; four in five athletes in the sweat data were male.¹
• A label cannot tell you your own sweat sodium, which ranged from 18 to 71 mmol/L across 506 athletes.¹

Frequently asked questions

Are electrolyte tablets good for you?

A tablet is a format; its milligrams and cautions matter. No trial has compared tablets with powders or drinks at serving amounts.

What is the best electrolyte for women?

No trial has tested a formula for women. The same checklist applies; in pregnancy, keep caffeine under 200 mg a day and ask a pharmacist.¹¹

Do electrolytes have caffeine?

Some do; a supplement with added caffeine must say "Contains caffeine" and give the amount.¹⁰

What is the healthiest electrolyte drink?

For most days the NHS says "Water or diluted sugar-free squash are good choices."¹⁵ In the 72-man trial, funded by a hydration research institute whose advisory board the lead author chaired, a rehydration solution and milk left about 300 g less urine than water over four hours.⁴ In 11 people dehydrated in the heat, low-fat milk kept positive fluid balance where water and a sports drink did not (dairy-industry-funded).³

Sources

1. Baker LB et al. J Sports Sci 2016. Observational, 506 athletes; sports-drink-industry authors. PubMed 26070030
2. Shirreffs SM et al. Med Sci Sports Exerc 1996. Randomised trial, 12 men, 7.5 hours; funding not checked. PubMed 8897383
3. Shirreffs SM et al. Br J Nutr 2007. Randomised crossover trial, 11 people, 5 hours; dairy-industry-funded. PubMed 17459189
4. Maughan RJ et al. Am J Clin Nutr 2016. Randomised trial, 72 men, 4 hours; funded by a hydration research institute whose advisory board the lead author chaired. PubMed 26702122
5. NHS. Salt in your diet. Page last reviewed 17 April 2023 (review overdue); checked 13 October 2026. nhs.uk
6. NHS. Vitamins and minerals: others. Page last reviewed 3 August 2020 (review overdue); checked 13 October 2026. nhs.uk
7. Retained Regulation (EU) 432/2012, Annex (permitted health claims). legislation.gov.uk
8. Urwin CS et al. Int J Sport Nutr Exerc Metab 2021. Review of 33 studies. PubMed 33440332
9. Retained Regulation (EU) 1169/2011, Annex XIII (reference values). legislation.gov.uk
10. Retained Regulation (EU) 1169/2011, Annex III (sweetener, polyol, caffeine statements). legislation.gov.uk
11. NHS. Water, drinks and hydration. Page last reviewed 17 May 2023 (review overdue); checked 13 October 2026. nhs.uk
12. Graudal NA et al. Cochrane Database Syst Rev 2020. Pooled analysis of 195 randomised trials. PubMed 33314019
13. Filippini T et al. J Am Heart Assoc 2020. Pooled analysis of 32 randomised trials. PubMed 32500831
14. Sarnowski A et al. Int J Nephrol Renovasc Dis 2022. Narrative review. PubMed 35942480
15. NHS. Dehydration. Page last reviewed 1 May 2026; checked 13 October 2026. nhs.uk

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