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Electrolytes

Electrolytes are minerals such as sodium, potassium and magnesium. They are most studied for rehydration in diarrhea and during long exercise.

Strongest evidenceHydrationStrong, 1,008 studies
Median dose in studies1,500 mg a dayFrom 63 study groups
Sodium, adequate intake (US, ages 19 to 50)1,500 mg a dayWHO advises adults to eat less than 2,000 mg a day.
Magnesium from supplements, upper limit350 mg a dayUS adults. No upper limit is set for sodium or potassium.
Ask a doctor or pharmacist first

Ask a doctor or pharmacist before you take electrolyte supplements if one of these applies to you:

  • You have kidney disease: the kidneys may not remove extra potassium and magnesium, and blood levels can rise too high.[1][2]
  • You take an ACE inhibitor, an angiotensin receptor blocker or a potassium-sparing diuretic: these medicines keep potassium in the body.[1]
  • You have heart failure, liver disease, type 1 diabetes or adrenal insufficiency: these raise the risk of too much potassium in the blood.[1]
  • You have high blood pressure: in trials, less sodium lowered blood pressure.[3]
  • You take a tetracycline or quinolone antibiotic, or a bisphosphonate for the bones: magnesium lowers their absorption, so the doses must be taken hours apart.[2]
  • A baby or young child has diarrhea or vomiting: a pharmacist can say which rehydration solution fits, and some signs need urgent help.[4]

Overview

What are electrolytes?

Electrolytes are minerals that carry an electric charge in blood and other body fluids: sodium, potassium, chloride, magnesium, calcium, phosphate and bicarbonate.[5] They help balance the water in the body and help nerves, muscles and the heart work.[5] The body gets them from food and drinks and loses them in sweat; plain water contains very little of them.[6] Products include oral rehydration solutions, which are powders mixed with water, and sports drinks with carbohydrate and electrolytes.[4][7]

What are electrolytes used for?

Rehydration has the best evidence (essential health). In children with diarrhea, oral rehydration solution worked about as well as a drip in 17 trials, though 1 child in 25 still needed the drip.[8] After exercise, drinks with sodium and sugar kept more fluid in the body than water did.[7][9] For fitness, carbohydrate-electrolyte drinks gave a small gain in endurance in warm conditions in 21 studies.[10] For gut health, a mineral water rich in magnesium sulfate eased constipation in one trial in women.[11] For heart health, potassium supplements lowered blood pressure in trials, with moderate certainty.[3] Evidence on muscle cramps is weak.[12]

Are electrolyte supplements safe?

For healthy adults, US and Canadian experts found too little evidence of harm to set an upper limit for sodium or potassium. They add that this does not mean any amount is safe.[3] The US upper limit for magnesium from supplements is 350 mg a day; more can cause diarrhea, nausea and stomach cramps.[2] Too much potassium is a risk with kidney disease and with some blood pressure and heart medicines.[1] Almost all populations eat more sodium than WHO advises.[13] In long races, drinking too much fluid can lower blood sodium to a dangerous level.[14]

How it works

Electrolytes are minerals that carry an electric charge in blood and other body fluids. The main ones are sodium, potassium, chloride, magnesium, calcium, phosphate and bicarbonate.[5] The body gets them from food and drinks, and loses them in sweat, urine and stool.[5][6][1]

  1. Gut absorption

    The small intestine takes up sodium together with glucose, and water follows them. Water uptake is fastest from a drink with sodium and glucose that is less concentrated than body fluids.[15][16] The gut absorbs about 90% of the potassium in food.[1]

  2. Fluid balance

    Sodium is the main regulator of the fluid outside cells, including the blood plasma. Most potassium stays inside cells, at a level about 30 times higher than outside.[1]

  3. Nerves and muscles

    A pump in the cell membrane, the sodium-potassium ATPase, keeps this difference. Nerves need it to send signals, and muscles need it to contract.[1] Magnesium helps move calcium and potassium across cell membranes, which a normal heart rhythm also needs.[2]

  4. Loss in sweat

    Sweat takes water and sodium out of the body. How much people sweat, and how salty their sweat is, differs a lot between people.[17] Diarrhea and vomiting take out water with sodium, chloride, potassium and bicarbonate.[18]

  5. Kidney control

    The kidneys control how much potassium and magnesium leave the body. In healthy people they pass the extra into urine.[1][2]

Benefits and studies

Each row is one benefit. The square shows the grade and the number of studies. Open a row to see the most trusted studies.

StrongModerateWeakNo trials
BenefitMain effects in studiesStudiesPeople

Dose

The WHO oral rehydration solution for diarrhea is clean water with salt and sugar. Since 2004, its osmolarity (a measure of how concentrated a drink is) is below 270 mOsm/L.[18][19] For US adults, the adequate intake is 1,500 mg of sodium a day (ages 19 to 50) and 2,600 mg (women) to 3,400 mg (men) of potassium.[3][1]

Usual dose

In one trial after exercise, athletes drank a volume equal to the body weight they had lost. The oral rehydration solution had 45 mmol of sodium per litre, the sports drink 18 mmol.[9] In cycling of 1 to 2 hours, performance rose with 0.15 to 0.20 mL of fluid per kg of body weight per minute.[20]

Daily need

Sodium: 1,500 mg a day for adults aged 19 to 50 in the US and Canada.[3] Potassium: 3,400 mg for men and 2,600 mg for women aged 19 and over; 2,900 mg in pregnancy and 2,800 mg while breastfeeding (ages 19 to 50).[1] Magnesium: 400 to 420 mg for men and 310 to 320 mg for women.[2]

Form

Oral rehydration solutions are powders that are mixed with water.[4] In supplements, potassium is often potassium chloride, and also citrate, phosphate, aspartate, bicarbonate or gluconate. Most potassium-only supplements contain up to 99 mg.[1] Labels give the amount of the mineral itself, not of the whole salt.[1][2] One gram of salt contains 400 mg of sodium.[13]

When to take

Drinking during moderate cycling raised performance when the ride lasted more than 1 hour; in hard cycling of 1 hour, it lowered performance by 2.5%.[20] In two cramp trials, the drink was taken during exercise or at the start of a cramp.[21][22]

How long

The exercise trials tested a drink on the day of one exercise session.[10][9] The pickle juice trial in people with cirrhosis lasted 28 days.[22]

Upper limit

No upper limit is set for sodium or potassium, because the evidence on harm was too weak; this does not mean that any amount is safe.[3] WHO advises adults to eat less than 2,000 mg of sodium a day, and the US Daily Value is less than 2,300 mg.[13][23] The US upper limit for magnesium from supplements is 350 mg a day for adults.[2]

Doses in studies

Most studies gave 500 to 1,000 mg a day, for 1 week or less.

The counts are study groups. A study group is one set of people in a study who took the same dose. One study can have several groups. These are amounts from studies, not advice for you.

How much a day63 groups in 44 studies
  1. Up to 25 mg3 groups
  2. 25 to 50 mg5 groups
  3. 50 to 100 mg3 groups
  4. 100 to 250 mg6 groups
  5. 250 to 500 mg0 groups
  6. 500 to 1,000 mg11 groups
  7. 1,000 to 2,500 mg9 groups
  8. 2,500 to 5,000 mg10 groups
  9. 5,000 to 10,000 mg3 groups
  10. 10,000 to 25,000 mg5 groups
  11. 25,000 to 50,000 mg6 groups
  12. 50,000 mg or more2 groups
For how long137 groups in 95 studies
  1. 1 week or less92 groups
  2. 1 to 4 weeks9 groups
  3. 1 to 3 months18 groups
  4. 3 to 6 months0 groups
  5. 6 to 12 months2 groups
  6. More than a year16 groups
Half of the groups took less than 1,500 mg a day. Half took more.Half of the groups took 200 to 4,950 mg a day. A quarter took less, a quarter took more.46 of 63 groups took 500 mg a day or more. Do not copy a study dose without a doctor.

Taken together

41 of 144 study groups took electrolytes with something else. This shows what studies gave together, not what works together.

  1. Calcium13 studies22
  2. Vitamin D3 studies7
  3. Creatine3 studies3
  4. Magnesium3 studies3
  5. Potassium3 studies3
  6. Vitamin C3 studies3
Bars and numbers count study groups. A companion is shown only when at least 3 different studies gave it.

Protocols

What studies used when they gave electrolytes for one goal, or to a group of people.

Each protocol describes what studies used, for one goal or for one group of people. It is not advice for you: talk to a doctor before you start a supplement.

Questions

12 questions in 4 groups. Open one for the short answer; each has its own page with the full answer and sources.

Basics
Do you need electrolyte drinks every day?

Most people do not. Sodium deficiency is very unlikely in healthy people.[13] In 2021, adults around the world ate 4,278 mg of sodium a day on average, more than double the WHO advice of under 2,000 mg.[13] The US adequate intake for adults aged 19 to 50 is 1,500 mg.[3] In a trial of 413 athletes in an Ironman triathlon of about 12 hours, blood sodium was the same with salt tablets, dummy tablets or no tablets.[24] Electrolytes need replacing when losses are large, as with diarrhea, vomiting or heavy sweating.[4][5]

Open the answer with sources ›
What are the signs of low electrolytes?

The signs depend on which electrolyte is low. Low potassium can cause constipation, tiredness, muscle weakness and a general unwell feeling; severe cases can upset the heart rhythm.[1] Early signs of low magnesium are loss of appetite, nausea, vomiting, tiredness and weakness; later come numbness, cramps and an abnormal heart rhythm.[2] Low blood sodium during long exercise can cause bloating, vomiting, headache and confusion.[25] Common causes of an electrolyte imbalance are vomiting, diarrhea, heavy sweating, some medicines and kidney, heart or liver problems. A blood test called an electrolyte panel measures the main electrolytes.[5]

Open the answer with sources ›
Benefits
Do electrolytes help with dehydration from diarrhea?

Yes. Oral rehydration solution, clean water with salt and sugar, is the WHO treatment for diarrhea.[18] In a Cochrane review of 17 trials in 1,811 children, it worked about as well as fluids through a drip, though 1 child in 25 still needed the drip.[8] Solutions with less salt and sugar than the old WHO formula meant fewer drips.[26]

Read the full answer ›
Do electrolyte drinks improve endurance?

A little, in long exercise. In a 2026 review of 21 studies in warm conditions, carbohydrate-electrolyte drinks gave a small gain in aerobic endurance compared with water or a dummy drink.[10] In cycling, drinking raised performance by 2% to 3% in moderate rides of more than 1 hour, but lowered it in a hard 1-hour ride.[20]

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Do electrolytes prevent muscle cramps?

The evidence is weak. A 2026 review of 9 studies in 11,274 athletes found no consistent link between cramps and hydration; a past cramp was the strongest risk factor.[12] In two small lab trials, electrolyte drinks made cramps harder to trigger.[21][27] Magnesium is unlikely to prevent night cramps in older adults.[28]

Read the full answer ›
Does dehydration affect focus, and do electrolytes help?

Dehydration lowers mental performance a little. A 2018 review of 33 studies found small losses in thinking (cognition), mostly in attention, planning and coordination. The losses were larger when people lost more than 2% of body weight as water.[29] In a trial at 30 °C, water with an electrolyte capsule tended to protect mood best, but the colour of the drink also had an effect.[30]

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Do electrolytes affect blood pressure?

Sodium and potassium act in opposite directions. Trials show with high certainty that eating less sodium lowers blood pressure.[3] Potassium supplements lowered blood pressure in trials, more in people with high blood pressure, with moderate certainty.[3] In a review of 32 trials, the effect grew weaker above about 30 mmol of extra potassium a day. Above about 80 mmol, blood pressure rose again in people treated for high blood pressure.[31] Eating less sodium also lowered the risk of cardiovascular events, with moderate certainty.[3]

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Do electrolytes help with constipation?

Magnesium may help with constipation, a gut health problem. In a trial of 244 women, one group drank 1 litre a day of a mineral water rich in magnesium sulfate. After 2 weeks, constipation eased in 37.5% of them, against 21.1% with low-mineral water. One author worked for the water's maker.[11] Magnesium salts loosen stool because the gut does not absorb all of them.[2] Polyethylene glycol laxatives worked better than lactulose in 10 trials, but that review compared two laxatives and did not test electrolytes.[32]

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Safety
Can you have too many electrolytes?

Yes, though it is rare in healthy people. Too much potassium is a risk with kidney disease or with some blood pressure medicines.[1] More than 350 mg a day of magnesium from supplements can cause diarrhea, and very large doses are poisonous.[2] Almost all populations eat more sodium than WHO advises.[13] Drinking too much water in long races can lower blood sodium.[14]

Read the full answer ›
Which medicines interact with electrolyte supplements?

ACE inhibitors, angiotensin receptor blockers and potassium-sparing diuretics such as spironolactone keep potassium in the body, so extra potassium can raise blood levels too high.[1] Loop and thiazide diuretics do the opposite: they increase the loss of potassium and magnesium in urine.[1][2] Magnesium lowers the absorption of tetracycline and quinolone antibiotics: take these at least 2 hours before or 4 to 6 hours after it. Keep magnesium and bisphosphonates at least 2 hours apart.[2]

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Forms and timing
Are electrolyte drinks better than water?

After heavy sweating, usually yes, but not in every trial. After exercise, a sports drink kept 73.9% and an oral rehydration solution 76.9% of the fluid in the body, against 58.1% for water.[9] At rest, an oral rehydration solution and milk kept more fluid than water, but a sports drink did not.[33] After 60 minutes of cycling in the heat, a trial found no difference.[34]

Read the full answer ›
How is an oral rehydration solution different from a sports drink?

In one trial, the oral rehydration solution had more salt and less sugar than the sports drink: 45 mmol of sodium per litre and 2.5% carbohydrate, against 18 mmol and 6%.[9] The WHO solution for diarrhea has an osmolarity, a measure of how concentrated a drink is, below 270 mOsm/L.[19] For rehydration after exercise, a 2025 review suggests sports drinks with 4% to 9% carbohydrate when normal food is not available.[7] The NHS advises against fruit juice and fizzy drinks for young children with diarrhea or vomiting.[4]

Open the answer with sources ›

References

  1. Potassium: Fact Sheet for Health Professionals. NIH Office of Dietary Supplements. ods.od.nih.gov
  2. Magnesium: Fact Sheet for Health Professionals. NIH Office of Dietary Supplements. ods.od.nih.gov
  3. Summary - Dietary Reference Intakes for Sodium and Potassium. National Academies of Sciences, Engineering, and Medicine National Academies Press (NCBI Bookshelf), 2019. www.ncbi.nlm.nih.gov
  4. Dehydration. NHS, 2026. www.nhs.uk
  5. Fluid and Electrolyte Balance. MedlinePlus, US National Library of Medicine, 2024. medlineplus.gov
  6. Electrolytes: MedlinePlus Medical Encyclopedia. MedlinePlus, US National Library of Medicine, 2025. medlineplus.gov

Review history

  1. 9 Nov 2026CheckedReviewerChecked every claim against its source.
  2. 9 Nov 2026Page createdResearcherFirst edition, written from PubMed and public health sources.