Supplements

Electrolytes

Updated · 25 sources

Electrolytes are minerals that carry an electric charge in body fluids. The three most relevant to training are sodium, potassium and magnesium. They control fluid balance, nerve signals and muscle contraction. Most people meet their needs from food, but heavy sweating, vomiting or diarrhea, and especially diuretic drugs can push blood levels out of the safe range. In endurance events, the most common serious electrolyte problem is low blood sodium from drinking too much water, not from too little salt.

Electrolyte drinks and powders are marketed to lifters for hydration, “pumps” and cramp prevention. The evidence for cramps is weak: in large cohorts of endurance athletes, cramping was predicted by racing faster and by past cramps, not by dehydration or blood electrolyte levels. The strongest reasons to pay attention to electrolytes are drug-related: loop and thiazide diuretics can cause dangerously low potassium, potassium-sparing diuretics and some blood pressure drugs can cause dangerously high potassium, and the vomiting and diarrhea caused by GLP-1 drugs can lead to dehydration and kidney injury.

This page summarizes what the National Academies, the NIH Office of Dietary Supplements, sports medicine consensus statements, drug labels and clinical studies report. It is for education only and is not medical advice.

Property Detail
Type Essential minerals (sodium, potassium, magnesium, plus chloride, calcium and others); food components and dietary supplements
Sodium (adults) Adequate Intake 1,500 mg/day; reduce intake if above 2,300 mg/day (Chronic Disease Risk Reduction level)
Potassium (adults) Adequate Intake 3,400 mg/day (men), 2,600 mg/day (women); no upper limit set
Magnesium (adults) RDA 400–420 mg/day (men), 310–320 mg/day (women); upper limit 350 mg/day from supplements
Normal blood levels Sodium about 135 mmol/L or higher; potassium about 3.6–5.0 mmol/L; magnesium 0.75–0.95 mmol/L
Sweat sodium in athletes Predicted whole-body average 35.9 mmol/L (range 18.2–70.8), about 830 mg per liter of sweat
Doses in cited studies Oral rehydration solution matched to sweat losses; 1 mL/kg pickle juice; potassium-enriched salt (25% potassium chloride)
WADA status Electrolytes are not prohibited. Diuretics are prohibited at all times (S5). IV infusions over 100 mL per 12 hours are prohibited except in hospital, surgical or clinical settings

What it is

An electrolyte is any substance that splits into charged particles (ions) in water. In the body the key ones are:

  • Sodium. The main positive ion outside cells. The ODS describes sodium as “the main regulator of extracellular fluid volume, including plasma volume” (NIH ODS, Potassium).
  • Potassium. The main positive ion inside cells. The concentration inside cells is about 30 times higher than outside. This gradient, maintained by the sodium-potassium pump (Na+/K+ ATPase), is needed for nerve transmission, muscle contraction and kidney function (NIH ODS, Potassium).
  • Magnesium. An adult body holds about 25 g of magnesium, 50% to 60% of it in bone, and less than 1% in blood serum. The kidneys control magnesium balance and excrete about 120 mg a day (NIH ODS, Magnesium). For supplement forms and trial data, see Magnesium.
  • Chloride travels with sodium and is lost with it in sweat. Calcium and bicarbonate are also electrolytes; bicarbonate as a buffer supplement is covered on Sodium Bicarbonate.

Dietary reference intakes

In 2019, a National Academies committee updated the sodium and potassium values. It set Adequate Intakes (AIs) rather than RDAs because the data were insufficient to define an average requirement. For sodium, it also set the first Chronic Disease Risk Reduction Intake (CDRR), the level above which lowering intake is expected to reduce chronic disease risk (NASEM 2019).

Electrolyte Men 19+ Women 19+ Upper limit
Sodium AI 1,500 mg; CDRR: reduce if above 2,300 mg AI 1,500 mg; CDRR: reduce if above 2,300 mg None set (UL not determined)
Potassium AI 3,400 mg AI 2,600 mg None set
Magnesium RDA 400 mg (19–30 y), 420 mg (31+ y) RDA 310 mg (19–30 y), 320 mg (31+ y) 350 mg/day from supplements and medications only

Sources: NASEM 2019; NIH ODS, Potassium; NIH ODS, Magnesium.

The sodium AI of 1,500 mg/day was based partly on a balance study in which people under daily heat stress reached roughly neutral sodium balance at 1,525 mg/day (NASEM 2019). The potassium AIs do not apply to people with kidney disease or taking drugs that impair potassium excretion. No potassium UL was set because there is no evidence that high intakes cause high blood potassium in adults with normal kidneys (NIH ODS, Potassium).

Typical US diets are high in sodium and low in potassium. In NHANES 2013–2014, average potassium intake from food was 3,016 mg/day for men and 2,320 mg/day for women, and the Dietary Guidelines list potassium as a nutrient of public health concern. In NHANES 2013–2016, 48% of Americans got less magnesium from food than the average requirement (NIH ODS, Potassium; NIH ODS, Magnesium).

Sweat losses

Sweat is mostly water with sodium and chloride; potassium and magnesium losses in sweat are small. The ODS notes that only “a very small amount” of potassium is lost in sweat (NIH ODS, Potassium). Large datasets from athlete testing show how variable sodium losses are:

Study Athletes Key numbers
Baker et al., J Sports Sci 2016 506 team-sport and endurance athletes, 15–50 °C Predicted whole-body sweat sodium 35.9 ± 10.4 mmol/L (range 18.2–70.8); sweating rate 1.21 ± 0.68 L/h (range 0.26–5.73)
Barnes et al., J Sports Sci 2019 1,303 athletes Sweating rate highest in American football (1.51 L/h) and endurance (1.28 L/h); sweat sodium loss 55.9 and 51.7 mmol/h in those groups vs 27.2–34.6 mmol/h in baseball, basketball and soccer
Baker et al., J Appl Physiol 2022 1,944 sweat tests Individual and environmental factors explained only 17%–23% of the variation in sweat sodium; energy expenditure and season (a proxy for heat acclimatization) mattered most

Converted to milligrams (1 mmol of sodium = 23 mg), the average of 35.9 mmol/L is about 830 mg of sodium per liter of sweat, and an endurance athlete losing about 52 mmol/h loses roughly 1,200 mg of sodium per hour.

The American College of Sports Medicine (ACSM) advises drinking during exercise to prevent losing more than 2% of body weight from water deficit and to avoid excessive changes in electrolyte balance. Because sweat rates and sweat electrolyte content vary so much, it recommends individualized plans, using body weight before and after exercise to estimate sweat rate. It notes that drinks with electrolytes and carbohydrate can help more than water “under certain circumstances” (ACSM, Med Sci Sports Exerc 2007).

What the research shows

Exercise-associated hyponatremia

Hyponatremia means low blood sodium. Exercise-associated hyponatremia (EAH) is defined as a serum or plasma sodium below 135 mmol/L during or up to 24 hours after prolonged activity (Bennett et al., Wilderness Environ Med 2020). Severe cases cause brain swelling and can be fatal.

  • How common. At the 2002 Boston Marathon, 13% of 488 runners who gave a finish-line blood sample had hyponatremia (135 mmol/L or less) and 0.6% had critical hyponatremia (120 mmol/L or less). The strongest risk factors were weight gain during the race (odds ratio 4.2), a finishing time over 4 hours (odds ratio 7.4 vs under 3:30) and extremes of body mass index. The type of fluid, including sports drinks, did not predict it (Almond et al., N Engl J Med 2005).
  • Main cause. A 2017 review concluded that drinking beyond thirst and the release of vasopressin (the antidiuretic hormone that makes the kidneys hold water) are the most common causes. Sodium and volume depletion play a role in a subset of athletes (Hew-Butler et al., Front Med 2017).
  • Sodium pills did not help performance. In 266 runners in an 80 km ultramarathon stage, sodium supplement intake had no relationship with pace or finishing time. Dehydrated runners performed best, and the authors concluded the findings reinforce the message to avoid overhydration (Lipman et al., Sports Med Open 2021).

Gaining weight during exercise is a warning sign that fluid intake is outpacing losses. Adding sodium to drinks does not make large volumes of fluid safe.

Muscle cramps

Exercise-associated muscle cramps (EAMC) are painful, involuntary contractions during or after exercise. The popular explanation is dehydration and electrolyte loss. The evidence mostly points elsewhere:

  • Ironman cohort. In 210 triathletes, the 43 who cramped did not differ from the others in blood electrolytes or body weight change. Only faster race times and a history of cramping predicted cramps. The authors concluded that dehydration and electrolyte imbalance are not causes (Schwellnus et al., Br J Sports Med 2011).
  • Earlier Ironman study. Crampers had slightly lower post-race sodium (140 vs 143 mmol/L), but both values were normal, and body weight loss was the same. The cramping muscles showed higher electrical activity, consistent with a nerve-driven cause (Sulzer et al., Med Sci Sports Exerc 2005).
  • 2026 meta-analysis. Pooling 9 longitudinal studies with 11,274 participants, only a prior history of cramps was strongly linked to new cramps (about 4.4-fold higher odds). Hydration status showed no consistent association, and crampers actually had higher post-race potassium and magnesium (Costa et al., Muscle Nerve 2026).

Some lab studies suggest fluid composition matters after heavy fluid loss:

  • Water vs oral rehydration solution. In 10 men who lost 2% of body mass running downhill in the heat, drinking plain water afterward lowered the electrical frequency needed to trigger a calf cramp (making cramps easier to induce), while an oral rehydration solution raised it (Lau et al., BMJ Open Sport Exerc Med 2019). A second crossover study with drinks taken during exercise found the same pattern (Lau et al., JISSN 2021). These used electrically induced cramps in small groups, not cramps during real competition.
  • Pickle juice. In dehydrated men, about 74 mL of pickle juice shortened electrically induced cramps by about 49 seconds compared with water. Blood electrolytes barely changed in 5 minutes, so the authors proposed a reflex triggered in the mouth and throat rather than electrolyte replacement (Miller et al., Med Sci Sports Exerc 2010).
  • Magnesium. A Cochrane review found that magnesium is unlikely to prevent cramps in older adults and found no randomized trials for exercise cramps (Garrison et al., Cochrane 2020). See Magnesium for details.

Cramps are, however, a recognized warning sign of real electrolyte disturbance caused by drugs. The hydrochlorothiazide label lists muscle cramps among the warning signs of fluid or electrolyte imbalance (Hydrochlorothiazide).

Potassium and blood pressure

Higher potassium intake lowers blood pressure, especially in people with hypertension. A 2017 meta-analysis of 25 trials in people with hypertension found reductions of 4.48 mm Hg systolic and 2.96 mm Hg diastolic with potassium supplements, mostly potassium chloride (NIH ODS, Potassium). In the SSaSS trial, 20,995 older adults in rural China with prior stroke or high blood pressure used a salt substitute of 75% sodium chloride and 25% potassium chloride or regular salt. The substitute lowered stroke (rate ratio 0.86), major cardiovascular events (0.87) and death (0.88), without a significant rise in serious hyperkalemia events (Neal et al., N Engl J Med 2021). That safety result applies to the population studied. The ODS advises people with kidney disease or taking drugs that raise potassium to consult a clinician before using potassium-based salt substitutes (NIH ODS, Potassium).

Electrolytes, diuretics and GLP-1 drugs

Diuretics

Diuretics are the drug class most likely to cause dangerous electrolyte problems in lifters, because they are misused before contests and weigh-ins:

Diuretic type Examples Effect on electrolytes
Loop Furosemide, bumetanide Increase urinary potassium and magnesium loss; can cause hypokalemia, hyponatremia and hypomagnesemia
Thiazide Hydrochlorothiazide, chlorthalidone, metolazone Increase urinary potassium and magnesium loss; can cause hypokalemia and hyponatremia
Potassium-sparing Spironolactone, amiloride, triamterene Reduce potassium and magnesium excretion; can cause hyperkalemia

Sources: NIH ODS, Potassium; NIH ODS, Magnesium.

The ODS notes that more than 50% of people with clinically significant hypokalemia might also have magnesium deficiency, which increases urinary potassium loss, and that both should be treated together. Mild hypokalemia causes fatigue, constipation and muscle weakness. Moderate to severe hypokalemia (below about 2.5 mmol/L) can cause paralysis, breathing problems and heart rhythm disturbances (NIH ODS, Potassium).

Case reports from bodybuilding show what can happen:

  • Triamterene/HCTZ plus fluid restriction. A 22-year-old bodybuilder developed generalized muscle cramps, sensory loss, weakness of all four limbs and urinary retention, with a potassium of 1.8 mmol/L and a QTc interval of 625 ms on ECG. He recovered within 2 days with IV fluids and potassium (Pfisterer et al., Clin J Sport Med 2020).
  • Hypokalemic paralysis. A Vienna report describes paralysis from low potassium in a professional bodybuilder and notes that the extent of diuretic misuse in the sport is unknown but “may be regarded as substantial” (Mayr et al., Am J Emerg Med 2012).
  • Peak week. A 2021 review found a “dearth of evidence” supporting common peak-week practices, including manipulation of water and electrolyte intake (Escalante et al., BMC Sports Sci Med Rehabil 2021).

Combining potassium supplements or potassium salt substitutes with a potassium-sparing diuretic, an ACE inhibitor such as lisinopril or an ARB such as losartan or telmisartan raises the risk of hyperkalemia. The ODS advises monitoring potassium with these drugs, and states that people with kidney disease or on such drugs should consult a clinician before using salt substitutes (NIH ODS, Potassium). Hyperkalemia can be silent until it causes muscle weakness, paralysis or a life-threatening arrhythmia.

GLP-1 receptor agonists

GLP-1 drugs such as semaglutide and tirzepatide commonly cause nausea, vomiting and diarrhea, especially during dose increases. The Wegovy label carries a warning for “Acute Kidney Injury Due to Volume Depletion.” It reports postmarketing cases of acute kidney injury, some requiring hemodialysis, mostly in patients who became dehydrated from nausea, vomiting or diarrhea, and advises monitoring kidney function in such patients, especially during dose initiation and escalation (Wegovy label). The tirzepatide labels describe similar postmarketing reports (Tirzepatide).

Vomiting and diarrhea also deplete potassium: diarrhea causes direct losses in stool, and vomiting leads to kidney potassium losses through metabolic alkalosis (NIH ODS, Potassium). The combination of a GLP-1 drug, a large calorie deficit, hard training in the heat and diuretic use stacks several of the risk factors described on this page. We found no trial that tested routine electrolyte supplementation in people on GLP-1 drugs.

Side effects and risks

Too much sodium

The National Academies’ CDRR advises reducing sodium intake when it is above 2,300 mg/day, because lowering it reduces chronic disease risk, mainly through blood pressure (NASEM 2019). Heavy sweaters have higher needs during training, but salty electrolyte products add to an already high background intake for most people.

Too much potassium

In healthy people with normal kidneys, high food potassium is not dangerous. Very large doses of supplements or potassium salt substitutes can exceed the kidneys’ capacity and cause acute hyperkalemia even in healthy people. Case reports link very large supplement doses to heart abnormalities and death (NIH ODS, Potassium). Potassium chloride drug products providing more than 99 mg potassium have been linked to small-bowel lesions, which is why most US potassium supplements contain no more than 99 mg per serving. Salt substitutes vary from about 440 to 2,800 mg of potassium per teaspoon.

Too much magnesium

High doses of supplemental magnesium cause diarrhea, nausea and abdominal cramping. Very high doses can cause low blood pressure, irregular heartbeat and cardiac arrest, and fatal cases have been reported. The adult UL of 350 mg/day applies to supplements and medications, not food (NIH ODS, Magnesium).

Overdrinking

Drinking large volumes of water or low-sodium fluids beyond thirst during long events is the main cause of exercise-associated hyponatremia (Hew-Butler et al. 2017). Confusion, headache, nausea or vomiting with weight gain after a long event needs urgent medical assessment.

Sodium, potassium and magnesium are sold as foods and dietary supplements. Potassium chloride and other salts are also prescription drugs at higher doses. Electrolytes themselves are not prohibited in sport. Diuretics are prohibited at all times under class S5 of the WADA 2026 Prohibited List, as described on the Furosemide, Hydrochlorothiazide and Spironolactone pages. IV “hydration” or electrolyte drips can be a violation even when the contents are allowed: IV infusions or injections of more than 100 mL per 12-hour period are prohibited at all times, except those received during hospital admission, surgery or clinical investigations, or with a Therapeutic Use Exemption (USADA).

Key takeaways

  • Three that matter most. Sodium controls fluid volume, potassium sets the charge across cell membranes, and magnesium supports muscle and nerve function.
  • Sweat is mostly sodium. Athletes lose an average of about 830 mg of sodium per liter of sweat, with a fourfold range between people; potassium and magnesium losses are small.
  • Overdrinking is the bigger danger. Exercise-associated hyponatremia is driven mainly by drinking beyond thirst; 13% of tested Boston Marathon finishers had it.
  • Cramps are mostly not electrolyte deficiency. Large cohorts link cramps to racing faster and past cramps, not to blood electrolytes or dehydration; electrolyte drinks help only in small lab studies.
  • Diuretics are the real hazard. Loop and thiazide diuretics can cause life-threatening low potassium; potassium-sparing diuretics, ACE inhibitors and ARBs can cause high potassium, especially with potassium supplements.
  • GLP-1 drugs and dehydration. Vomiting and diarrhea on semaglutide or tirzepatide can cause volume depletion and acute kidney injury.
  • Watch IV drips in tested sport. More than 100 mL by IV in 12 hours is prohibited outside legitimate medical care.

Sources

  1. National Academies of Sciences, Engineering, and Medicine. Dietary Reference Intakes for Sodium and Potassium. Washington, DC: National Academies Press; 2019. National Academies Press.
  2. National Institutes of Health Office of Dietary Supplements. Potassium: fact sheet for health professionals. Updated June 2, 2022. NIH ODS.
  3. National Institutes of Health Office of Dietary Supplements. Magnesium: fact sheet for health professionals. Updated January 6, 2026. NIH ODS.
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  14. Costa LDS, Correa VAF, de Oliveira VF, et al. Risk factors for exercise-associated muscle cramps: a systematic review with meta-analysis. Muscle Nerve. 2026;74(5):1375–1386. PubMed.
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  20. Pfisterer N, Stöllberger C, Finsterer J. Severe acquired hypokalemic paralysis in a bodybuilder after self-medication with triamterene/hydrochlorothiazide. Clin J Sport Med. 2020;30(5):e172–e174. PubMed.
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