Electrolytes: who needs them and who doesn't

By the DieticiansWorldwide.com editorial team · 17 October 2026 · Supplements & industry

What electrolytes are and what they do

Electrolytes are minerals that carry an electric charge when dissolved in body fluids. The main ones are sodium, potassium, chloride, magnesium, calcium, phosphate and bicarbonate. The US National Library of Medicine explains that sodium "helps control the amount of fluid in the body" and also helps nerves and muscles work, while potassium helps "your cells, heart, and muscles work properly" (MedlinePlus).

You get these minerals from food and drink, and your kidneys keep blood levels within a narrow range. That is the key point for anyone deciding whether to buy an electrolyte powder: in a healthy person, the body is very good at balancing electrolytes on its own. Problems arise when losses are unusually large or fast, when fluid intake swings far from what you lose, or when illness or medicines interfere with the kidneys' control.

MedlinePlus lists the main causes of an electrolyte imbalance as certain medicines, severe vomiting or diarrhoea, heavy sweating, heart, liver or kidney problems, not drinking enough during intense exercise or very hot weather, and drinking too much water. Notice that last one. Over-drinking plain water is a real cause of low sodium, not just under-drinking.

Is electrolyte water healthy?

For most people on most days, electrolyte drinks are neither harmful nor necessary. They are an expensive way of getting minerals that a normal meal already supplies. Whether a particular product is "healthy" depends on what else is in it and how often you drink it.

Two ingredients deserve attention:

• Salt. Many people already eat too much. The World Health Organization recommends less than 2,000 mg of sodium (5 g of salt) a day for adults and estimates that the global average intake in 2021 was 4,278 mg, more than double that limit (WHO). A salty electrolyte drink that you do not need adds to that load.
• Sugar. The NHS advises adults to have no more than 30 g of free sugars a day, roughly seven sugar cubes (NHS). Some sports drinks and hydration mixes supply a large share of that in one bottle. As a yardstick, the UK soft drinks levy applies to drinks containing at least 5 g of sugar per 100 ml, with a higher rate from 8 g (HM Revenue and Customs).

For everyday hydration, the NHS recommends 6 to 8 cups or glasses of fluid a day, with more in hot weather or when you are active, and says water, lower-fat milk and lower-sugar drinks, including tea and coffee, all count (NHS, water, drinks and your health). Our water intake calculator gives you a personal starting estimate based on your size and activity.

Who benefits: a quick guide

The rest of this guide explains each row and the evidence behind it.

Exercise and heat: when sport really needs electrolytes

The best summary of the evidence is the 2016 joint position statement on nutrition and athletic performance from the Academy of Nutrition and Dietetics, Dietitians of Canada and the American College of Sports Medicine (Thomas and colleagues, Dietitians of Canada). It makes several points that are useful for anyone choosing a drink.

How much fluid you lose

Sweat rates during exercise range from about 0.3 to 2.4 litres an hour, depending on intensity, fitness, heat, humidity and altitude. Fluid losses of more than 2% of body weight "can compromise cognitive function and aerobic exercise performances, particularly in hot weather". A simple way to estimate your own losses is to weigh yourself before and after training: in the statement's words, a loss of 1 kg represents approximately 1 litre of sweat, after you account for drinks and toilet stops. For most athletes, a fluid plan of about 0.4 to 0.8 litres an hour suits, adjusted to tolerance.

When sodium matters

Sweat contains "substantial but variable amounts of sodium", with smaller amounts of potassium, calcium and magnesium. On average, sweat sodium is about 50 mmol per litre, roughly 1 g per litre, but this varies widely. The position statement says sodium should be taken during exercise when large sweat sodium losses occur, giving three scenarios:

• high sweat rates, above 1.2 litres an hour;
• salty sweat;
• prolonged exercise lasting more than 2 hours.

After exercise, sodium from food or drink helps you retain the fluid you drink, so athletes "should not be advised to restrict sodium" in recovery when losses have been large. Because you keep losing fluid after you stop, the statement suggests drinking 125% to 150% of the deficit, for example 1.25 to 1.5 litres for every kilogram lost.

What sports drinks can legally claim

In the UK and EU, a "carbohydrate-electrolyte solution" may claim to help maintain endurance performance during prolonged exercise, and to enhance the absorption of water during exercise, only if it meets set conditions. It must provide 80 to 350 kcal per litre from carbohydrate, contain 20 to 50 mmol of sodium per litre (460 to 1,150 mg), and have an osmolality between 200 and 330 mOsm/kg (retained Regulation (EU) No 432/2012). In other words, the drinks with authorised benefits contain both carbohydrate and a meaningful amount of sodium. A zero-calorie drink with a sprinkle of minerals cannot make those claims.

Australia's national sports institute lists both sports drinks and electrolyte supplements among the sports foods with evidence for use in specific situations, describing electrolyte products as designed to replace fluid and electrolytes, "in particular, sodium and potassium", lost through sweat (Australian Institute of Sport). The position statement's caution applies too: sports foods cost more than whole foods and "may be used unnecessarily".

The risk most people overlook: drinking too much

Hyponatraemia, or low blood sodium, is the more dangerous fluid problem in sport. The position statement says over-drinking "in excess of sweat and urinary losses is the primary cause", that it is typically seen in recreational athletes who sweat less but drink more, and that women appear to be at greater risk. Symptoms can include bloating, nausea, vomiting, headache and confusion and, in severe cases, seizures and loss of consciousness. Electrolyte drinks contain far less sodium than blood, so they do not make it safe to drink unlimited amounts. Drink to a plan, not to a schedule of "as much as possible".

Children and teenagers

The American Academy of Pediatrics warned in 2011 that frequent or excessive intake of caloric sports drinks "can substantially increase the risk for overweight or obesity" in children and adolescents, and that energy drinks have no place in their diets (American Academy of Pediatrics, Pediatrics 2011). The NHS advises that children should avoid sugary fizzy drinks, squash and juice drinks completely, so for most school sport, water is the drink to reach for.

Diarrhoea and vomiting: should you drink electrolytes?

Yes, if you are at risk of dehydration, but choose the right product. Illness is where electrolyte replacement has its strongest evidence, and where sports drinks are the wrong tool.

The World Health Organization describes oral rehydration solution (ORS) as "a mixture of clean water, salt and sugar" that is "absorbed in the small intestine and replaces the water and electrolytes lost in the faeces", and notes that diarrhoea still kills around 443,832 children under five every year (WHO). The glucose in ORS is there to help sodium and water absorption, in carefully balanced amounts. A systematic review of 15 randomised trials in 2,397 children found that the reduced-osmolarity formula WHO now uses led to fewer unplanned intravenous drips than the older formula (odds ratio 0.61), with less vomiting and lower stool output (Hahn and colleagues, BMJ, 2001).

For most adults with a short stomach bug, the NHS advice is simple: drink lots of fluids, such as water or squash, in small sips if you feel sick, and avoid fruit juice and fizzy drinks because "they can make diarrhoea worse" (NHS). It recommends speaking to a pharmacist about oral rehydration powder if you have signs of dehydration, such as dark, smelly pee or peeing less than usual, or if you are older, have a weakened immune system or other conditions that raise your risk.

Why not a sports drink? The Australian Institute of Sport describes sports drinks as designed to let an athlete "simultaneously rehydrate and refuel" during exercise. They are not formulated to replace the water and salts lost in diarrhoea the way ORS is, so pharmacy sachets are the better tool when you are ill.

Know when home care is not enough. The NHS says babies, children and older adults are more at risk of dehydration (NHS, dehydration). Get urgent advice if a child under five has signs of dehydration, such as fewer wet nappies, if you cannot keep fluids down, or if symptoms persist after using rehydration sachets.

GLP-1 medicines: nausea, diarrhoea and dehydration

More people now take GLP-1 receptor agonists such as semaglutide for diabetes or weight management, and stomach side effects are common. In the 68-week trials summarised in the European product information for semaglutide for weight management, nausea affected 43.9% of people taking it against 16.1% on placebo, diarrhoea 29.7% against 15.9%, and vomiting 24.5% against 6.3% (European Medicines Agency). Most episodes were mild to moderate, with median durations of 8 days for nausea, 2 days for vomiting and 3 days for diarrhoea.

The same document warns that nausea, vomiting and diarrhoea "may cause dehydration, which in rare cases can lead to a deterioration of renal function", and says patients should "take precautions to avoid fluid depletion". Smaller appetites make this harder, because food normally supplies a lot of both water and sodium.

Practical steps, which a dietitian can tailor:

1. Sip fluids steadily through the day rather than drinking large amounts at once, which can worsen nausea.
2. Keep some savoury foods in your diet, such as soup or broth, unless you have been told to limit salt.
3. Use pharmacy ORS if you develop diarrhoea or vomiting and show signs of dehydration.
4. Do not use daily electrolyte powders as a default. If you are well and eating, they add salt and cost without clear benefit.
5. Tell your prescriber if sickness or diarrhoea continues, especially if you have kidney disease or take diuretics or blood pressure medicines.

If you are weighing medicines against supplements marketed for weight loss, our review of berberine, the so-called "nature's Ozempic" explains how the evidence compares. Constipation is also common with these medicines; building up high-fibre foods gradually, with enough fluid, can help.

Signs of an electrolyte imbalance

Symptoms are vague and overlap with many other conditions, which is why a blood test, not a guess, decides. Dehydration often shows first as dark yellow, strong-smelling urine, peeing less often and feeling dizzy or lightheaded, according to the NHS. Low sodium can cause headache, nausea and confusion, as described above. MedlinePlus notes that an electrolyte panel, a standard blood test, checks the main electrolytes, and that treatment depends on which mineral is too high or too low and why.

Treat muscle cramps with caution as a sign. The 2016 position statement says cramps "are typically caused by muscle fatigue", although they may be associated with dehydration and electrolyte imbalances in people who sweat heavily and are not used to the heat. Electrolyte drinks are not a reliable cure for cramp. Magnesium is often marketed for cramp too; our review of magnesium glycinate looks at that evidence.

Who should be careful with electrolyte products

Some people should not use electrolyte products, or salt substitutes, without advice:

• People with kidney disease, who may struggle to clear potassium and need individual fluid and salt targets.
• People with heart failure or high blood pressure, who are often advised to limit sodium and sometimes fluid.
• People taking certain blood pressure medicines. NICE advises that potassium-chloride salt substitutes "should not be used by older people, people with diabetes, pregnant women, people with kidney disease and people taking some antihypertensive drugs, such as ACE inhibitors and angiotensin II receptor blockers" (NICE NG136). The same caution makes sense for high-potassium electrolyte powders.
• Children, for whom adult powders and tablets may be too concentrated.
• Anyone on a fluid restriction, which no hydration product overrides.

Food first: getting electrolytes without a powder

For everyday life and most training, food does the job. Potassium comes from fruit, vegetables, beans, lentils, milk, yoghurt and potatoes. Sodium is already plentiful in bread, cheese, soups and many savoury foods. Magnesium comes from whole grains, nuts, seeds and leafy greens, and calcium from dairy or fortified alternatives. Because sodium in food helps you hold on to the fluid you drink, a normal meal with a drink is usually all the recovery that a short session needs.

If you want to check whether your overall diet already covers these foods, try our healthy eating check.

What labels and testing do and do not tell you

Electrolyte powders and tablets are sold as foods or supplements, not medicines. Read the panel for sodium per serving in milligrams, potassium, sugar per serving and the number of servings you would actually use. Be sceptical of claims such as "hydrates three times faster than water" unless they are backed by authorised claims or published trials.

Independent quality seals tell you something useful but limited. The US National Institutes of Health explains that a seal indicates a product "was properly manufactured, contains the ingredients listed on the label, and does not contain harmful levels of contaminants", but "these seals do not guarantee that a product is safe or effective" (NIH Office of Dietary Supplements). For athletes in drug-tested sport, the Australian Institute of Sport warns that inadvertently taking a prohibited substance "is a known risk of taking some supplements" (AIS, supplements in sport), which is why batch-tested products and advice from a sports dietitian matter.

The same evidence-first approach applies to every product in your cupboard. Our reviews of vitamin D supplements and colostrum, which is heavily marketed to athletes, apply it to two more. For the wider picture, start at our supplements hub.

The bottom line

• Most days: water and food are enough. Use your thirst and pale urine as a guide.
• Long or hot exercise: plan fluids and sodium, especially for sessions over two hours, heavy sweaters and salty sweaters. Do not over-drink.
• Illness: pharmacy oral rehydration solution, not sports drinks, if you are at risk of dehydration.
• GLP-1 medicines: sip steadily, use ORS for diarrhoea or vomiting, and keep your prescriber informed.
• Kidney, heart or blood pressure conditions: ask your clinical team before using any electrolyte product.

If you train for endurance events or have a medical condition that affects fluid balance, a sports or clinical dietitian can build a personal plan. Not sure which kind of professional you need? Our short tool can point you in the right direction.

Find the right nutrition professional for you