Verdict: Useful for long or hot events and heavy sweaters, unnecessary for most runs under an hour, and never a reason to drink more than thirst asks for.
Safety: Overdrinking, even with electrolyte drinks, can cause dangerous hyponatraemia; people with high blood pressure, heart or kidney disease should ask a doctor about extra sodium
Key takeaways
Electrolytes do not raise VO2max, but losing more than about 2% of body weight as fluid is linked to worse performance
Overdrinking, not a lack of sodium, is the main cause of exercise-associated hyponatraemia, and drinking to thirst is the recommended default
Weighing yourself before and after a run is the simplest way to estimate your sweat rate and plan fluids for a marathon or a hot, humid race
Electrolyte drinks, tablets and powders are everywhere at races. They have a real role in long and hot events, but they don't raise VO2max, they rarely prevent cramps, and drinking too much — even of an electrolyte drink — can be dangerous. Here is what the evidence supports.
What it is
Electrolytes are minerals that carry an electrical charge in body fluids. For exercise, the most important is sodium, the main electrolyte lost in sweat, followed by chloride, potassium and smaller amounts of magnesium and calcium. Sodium helps hold water in the bloodstream, supports nerve and muscle function and makes fluids more palatable, which encourages drinking. Sports drinks also usually contain carbohydrate.
Does it raise VO2max?
No. VO2max is set by the heart, blood and muscles (see what limits VO2max), and electrolytes do not change that ceiling. What they can do is help you avoid dehydration, which reduces blood volume and makes the heart work harder at the same pace. The American College of Sports Medicine position stand (Sawka 2007) sets the goal of drinking during exercise as preventing excessive dehydration, defined as more than about 2% of body weight lost as water, and excessive changes in electrolyte balance, to avoid compromised performance.
Does it improve endurance performance?
For short runs, there is no meaningful benefit over water. In long events and hot conditions, the picture changes: the ACSM statement notes that drinks containing electrolytes and carbohydrate can offer benefits over water alone under certain circumstances, and recommends customised fluid plans because sweat rates and sweat sodium vary a lot between people.
But more sodium is not always better. In a study of the 161-km Western States Endurance Run, Hoffman and Stuempfle (2015) found that 93.9% of runners used sodium supplements and 6.6% of finishers developed hyponatraemia. Sodium intake rate did not differ between those with low and normal blood sodium, and the authors concluded that overhydration was the primary characteristic of runners who developed hyponatraemia.
Hyponatraemia: the real risk of overdrinking
Exercise-associated hyponatraemia (low blood sodium) is a preventable and potentially fatal condition. The 2015 international consensus statement led by Hew-Butler concluded that drinking according to thirst is sufficient to prevent both dehydration and hyponatraemia in most situations. Warning signs include headache, nausea, vomiting, bloating, confusion and swelling of the hands — symptoms that can be mistaken for dehydration. Slower runners who drink at every aid station over many hours are at particular risk. Electrolyte drinks do not make overdrinking safe, because they contain far less sodium than blood.
How it is used in studies
Research and guidelines favour a personal plan over a fixed dose:
- Sweat-rate test: weigh yourself nude before and after a run of about an hour, add the weight of any fluid you drank, and subtract any toilet breaks. Each kilogram lost is roughly a litre of sweat. A review by Baker (2017) notes that changes in body mass are the simplest and most accurate field method.
- Sweat sodium: patch tests and labs can estimate how salty your sweat is, but results depend heavily on method. If your kit is crusted with white salt after runs, you are probably a salty sweater.
- Race plan: drink to thirst, use sodium-containing drinks or gels in long or hot races, and aim to finish having lost some weight rather than gained it.
- Stomach: practise in training. Concentrated salt tablets and strong drinks can cause nausea; dilute them or spread intake out.
- Recovery: after long or hot sessions, fluids plus a salted meal restore what you lost.
Training in heat and humidity
Hot, humid climates such as Bangkok, Singapore or a summer race in the tropics raise sweat rates and make dehydration more likely, while high humidity limits how well sweat cools you. Gradual heat acclimatisation improves tolerance and changes sweat responses (see heat training and VO2max). Expect slower paces and higher heart rates in the heat, and adjust effort rather than fighting it with extra fluids — see VO2max and heart rate zones.
Side effects, safety and anti-doping
- Hyponatraemia from overdrinking is the most serious risk.
- Stomach upset from concentrated products.
- High sodium intake can be a problem for people with high blood pressure, heart failure or kidney disease. Talk to a doctor if you have a condition or take medication such as diuretics.
- Anti-doping: electrolytes are not prohibited, but competitive athletes should use third-party tested products.
This page is not medical advice.
Who might benefit
- Marathon, ultra and triathlon athletes racing for more than two hours
- Runners training or racing in hot, humid conditions
- Heavy or salty sweaters
Bottom line
Electrolytes won't raise your VO2max, and most short runs need nothing but water. For marathons and hot races, sodium-containing drinks and a plan based on your own sweat rate are sensible, as long as you drink to thirst and never overdrink. Compare other options on the supplements page, read about magnesium for cramps, and track your fitness with the VO2max calculator.
Frequently asked questions
Do I need electrolytes for running?
For most runs under an hour, water and normal meals are enough. Electrolytes become more useful for long runs, marathons, hot and humid conditions and heavy, salty sweaters.
Should I take electrolytes during a marathon?
Many runners use a sports drink or gels with sodium during a marathon, especially in the heat. Drink to thirst rather than to a schedule, because too much fluid can dilute blood sodium even if it contains electrolytes.
Can electrolytes upset your stomach when running?
Yes. Concentrated salt tablets or strong drinks can cause nausea or stomach upset in some runners. Practise your race-day drinks in training and dilute them if needed.
Do electrolytes help recovery after running?
After long or hot sessions, replacing fluid and sodium helps you rehydrate faster. A normal meal with some salt and fluids does the same job for most people.
Do electrolytes prevent muscle cramps?
Probably not for most runners. A study of 210 Ironman triathletes linked cramps to faster racing and previous cramps rather than to dehydration or blood sodium changes.
Sources
- American College of Sports Medicine; Sawka MN, Burke LM, Eichner ER, Maughan RJ, Montain SJ, Stachenfeld NS. Exercise and fluid replacement. Med Sci Sports Exerc. 2007. PMID 17277604.
- Hew-Butler T, Rosner MH, Fowkes-Godek S, et al. Statement of the Third International Exercise-Associated Hyponatremia Consensus Development Conference, Carlsbad, California, 2015. Clin J Sport Med. 2015;25(4):303–320. PMID 26102445.
- Hoffman MD, Stuempfle KJ. Sodium supplementation and exercise-associated hyponatremia during prolonged exercise. Med Sci Sports Exerc. 2015. PMID 25551404.
- Baker LB. Sweating rate and sweat sodium concentration in athletes: a review of methodology and intra/interindividual variability. Sports Med. 2017. PMID 28332116.
- Schwellnus MP, Drew N, Collins M. Increased running speed and previous cramps rather than dehydration or serum sodium changes predict exercise-associated muscle cramping: a prospective cohort study in 210 Ironman triathletes. Br J Sports Med. 2011. PMID 21148567.