Electrolytes and sodium for runners: what's being used and what the research says
We report what runners are using and what the research says. We don't recommend taking any supplement. Talk to your GP or a registered sports dietitian before trying one.
Quick answer
Runners lose sodium in sweat, and how much varies widely from person to person[1]. In some situations, drinks with electrolytes and carbohydrate can help more than water alone[2], but in a 161 km ultramarathon, cramps and low blood sodium were unrelated to how much sodium runners took in[3].
- Research
- Emerging (proposed)Can help replace sweat losses in long, hot events. No good evidence that extra sodium prevents cramps or low blood sodium.
- Proposed by our editor; not yet confirmed by an expert reviewer.
- WADA status
- Permitted
- Distances in the research
- 800 m–5K: not studied10K–half: limited researchMarathon: limited researchUltra: studied
What are electrolytes and sodium?
Sweat carries water and electrolytes out of the body, chiefly sodium[1].
Runners get them from sports drinks with electrolytes and carbohydrate[2] and from salt capsules or tablets[4][5].
Also called: salt tablets, salt capsules, electrolyte drinks.
Why are electrolytes getting attention?
Salt tablets are widely used: in a 2024 survey of 5,668 Chinese marathon runners, 54% of those who used supplements said they used salt tablets[5].
Many ultrarunners believe sodium prevents cramps and low blood sodium: in a survey of 1,152 ultramarathon runners, two-thirds wanted sodium supplements at races for those reasons[4].
How do electrolytes work?
Sweat removes water and sodium, and both sweat rate and sweat sodium differ widely between runners[1][2]. In one trial, triathletes given salt capsules had higher blood sodium after a race, and tended to lose less body weight[6].
Low blood sodium during exercise, called exercise-associated hyponatraemia, is most often caused by drinking beyond thirst, together with the water-retaining hormone vasopressin; sodium loss plays a part in a smaller number of cases[7].
Do runners need electrolyte supplements?
Research suggests extra sodium beyond food and drink is generally not needed, even in ultramarathons[4][3], though one triathlon trial found salt capsules helped[6]. Drinks with electrolytes and carbohydrate can help more than water alone in some situations[2].
800 m to 5K (Not studied)
We found no studies of electrolyte supplements in races of these lengths. The research is on long events, where far more sweat is lost[1].
10K to half marathon (Limited research)
There is little research at these distances. Sweat rates and sweat sodium vary so much between runners that losses over an hour or two can be small for one runner and large for another[1].
Marathon (Limited research)
In a survey of 210 marathon runners, fewer than 5% named drinking to thirst, the guidance of the 2015 consensus on low blood sodium, and slower runners tended to plan to drink more often, though the difference was not statistically significant[8]. Drinking beyond thirst is the most common cause of low blood sodium[7].
Ultra (Studied)
In a 161 km race in heat up to 39 °C, cramping, dehydration, low blood sodium and nausea were unrelated to how much sodium runners took in. Runners who took in more sodium lost less weight, but the authors judged the losses in low-sodium runners, up to 4 to 5%, acceptable[3].
In a different long event, a half-ironman triathlon, the group given salt capsules in a randomised trial finished faster and had higher blood sodium than the control group[6].
The key studies, in order
- 2007ConsensusSweat rates and sweat electrolytes vary between people; drinks with electrolytes and carbohydrate can help more than water alone in some circumstances. [2]
- 2009Expert reviewThe electrolyte-loss explanation for cramps rests mainly on anecdote and case reports; four cohort studies don't support it, and evidence points to altered neuromuscular control. [13]
- 2015ConsensusThe 2015 international consensus on exercise-associated low blood sodium: drinking beyond thirst is the main cause, and it advises drinking to thirst. [9]
- 2015Observational study20 finishers of a 161 km race in heat up to 39 °C: cramping, dehydration, low blood sodium and nausea were unrelated to how much sodium they took in. [3]
- 2016Trial26 triathletes: the salt-capsule group finished a half-ironman faster, with higher blood sodium afterwards, than the control group. [6]
- 2017Expert reviewSweat rate and sweat sodium vary widely between and within athletes; sweat tests can give inconsistent results unless done carefully. [1]
- 2017Expert reviewDrinking beyond thirst, together with the hormone vasopressin, is the most common cause of low blood sodium during exercise. [7]
- 2018ConsensusOnly a few performance supplements, including caffeine, creatine, nitrate and sodium bicarbonate, have good evidence. Responses vary between people, and contamination is a known anti-doping risk. [12]
- 2020Survey1,152 ultrarunners: two-thirds wanted sodium supplements at races, believing they prevent low blood sodium and cramps; the evidence says extra sodium is generally not needed. [4]
- 2022Survey210 marathon runners: fewer than 5% named drinking to thirst, the 2015 consensus guidance. Slower and first-time runners knew least about low blood sodium. [8]
- 2025Survey5,668 marathon runners surveyed in 2024: among those who used supplements, more than 90% used energy gels and 54.4% used salt tablets. [5]
What the research can't tell us yet
The ultramarathon findings come from an observational study of 20 finishers, not a trial[3]. The salt capsule trial was in 26 triathletes in one race[6].
Sweat tests used to personalise sodium intake can give inconsistent results unless they're done carefully[1].
How are electrolytes used in studies?
In the salt capsule trial, triathletes took capsules before and during the race[6].
In the 161 km ultramarathon, runners' total sodium intake ranged from about 2.5 g to 38 g, and on average two-thirds of it came from food and drink rather than capsules[3].
The 2015 consensus on low blood sodium advises drinking to thirst[9].
| What studies used | When | Ref. |
|---|---|---|
| Salt capsules totalling 113 mmol of sodium (about 2.6 g) | Before and during a half-ironman triathlon | [6] |
What are the side effects, and who should be careful?
The main risk isn't the salt, it's drinking too much: low blood sodium during exercise is most often caused by drinking beyond thirst[7], and ultrarunners rarely recognise that sodium supplements could lead to overhydration[4].
Salt tablets add to the salt already in your diet. The NHS says adults should have no more than 6 g of salt a day, and that too much salt can cause high blood pressure[10].
Be careful if
- You have high blood pressure or have been told to eat less salt: too much salt can cause high blood pressure[10].
- You plan to drink to a schedule in a long race: drinking beyond thirst is the most common cause of low blood sodium[7].
- You're a slower or first-time marathoner: in one survey, these runners knew least about low blood sodium, and slower runners believed more fluid was needed[8].
Are electrolytes allowed in competition?
Sodium and other electrolytes are not on the World Anti-Doping Agency's Prohibited List, so taking them by mouth is permitted. Intravenous infusions or injections of more than 100 mL in 12 hours are a prohibited method at all times, whatever they contain, unless received legitimately in hospital treatment, surgery or clinical investigations[11].
The anti-doping risk with any supplement product is contamination. Products can contain prohibited substances that aren't on the label, and under the World Anti-Doping Code an athlete is responsible for anything found in their sample, even if it got there by accident[12].
Independent quality-assurance schemes, often called batch testing, check supplement products for prohibited substances[12]. WADA says using a product from one of these schemes can reduce, but not eliminate, the risk of an anti-doping violation[11], and the IOC says no product can be guaranteed entirely safe[12].
Myth or evidence?
4 things runners hear about electrolytes and sodium. Pick an answer to see what the research says.
1.Salt tablets prevent muscle cramps.
2.Drinking too much is the most common cause of low blood sodium in runners.
Show the answer
Evidence. Drinking beyond thirst is the most common cause[7].
3.Every runner loses about the same amount of sodium in sweat.
Show the answer
Myth. Sweat rate and sweat sodium vary widely between runners[1].
4.Salt capsules improved race times in a triathlon trial.
Show the answer
Evidence. In a half-ironman trial, the salt-capsule group finished faster than the control group[6].
Have you tried electrolytes?
An anonymous reader poll. We store only the page, your answer and the time.
What readers have said so far
No answers yet. We show the results once 30 readers have answered.
A poll of readers who chose to answer, not a scientific survey.
Frequently asked questions
- Do runners need electrolyte supplements?
- Research suggests extra sodium beyond food and drink is generally not needed, even in ultramarathons[4], while drinks with electrolytes and carbohydrate can help more than water alone in some situations[2].
- Do salt tablets prevent cramps?
- The evidence doesn't support that. In a 161 km ultramarathon, cramping was unrelated to sodium intake[3], and research points to altered nerve and muscle control, not salt loss, as the main cause of cramps[13].
- What causes low blood sodium in runners?
- Most often, drinking beyond thirst[7].
- How much sodium do runners lose in sweat?
- It varies widely between runners and conditions, and sweat tests only help if they're done carefully[1].
- Are salt tablets popular with runners?
- Yes. In a 2024 survey of 5,668 Chinese marathon runners, 54% of those who used supplements said they used salt tablets[5].
- Is drinking to thirst enough?
- Guidance differs. The 2015 consensus on low blood sodium advises drinking to thirst[9], while the older ACSM position stand recommends individual drinking plans to limit body-weight loss to about 2%[2]. Drinking beyond thirst is the most common cause of low blood sodium[7].
References
- [1]
Baker LB Sweating rate and sweat sodium concentration in athletes: a review of methodology and intra/interindividual variability. Sports Medicine, 2017.
Expert reviewSweat rate and sweat sodium vary widely between and within athletes; sweat tests can give inconsistent results unless done carefully.
doi.org/10.1007/s40279-017-0691-5 - [2]
American College of Sports Medicine, Sawka MN, Burke LM, et al. American College of Sports Medicine position stand. Exercise and fluid replacement. Medicine and Science in Sports and Exercise, 2007.
Consensus statementSweat rates and sweat electrolytes vary between people; drinks with electrolytes and carbohydrate can help more than water alone in some circumstances.
doi.org/10.1249/mss.0b013e31802ca597 - [3]
Hoffman MD, Stuempfle KJ, Valentino T Sodium intake during an ultramarathon does not prevent muscle cramping, dehydration, hyponatremia, or nausea. Sports Medicine - Open, 2015.
Observational study20 finishers of a 161 km race in heat up to 39 °C: cramping, dehydration, low blood sodium and nausea were unrelated to how much sodium they took in.
doi.org/10.1186/s40798-015-0040-x - [4]
Hoffman MD, White MD Belief in the need for sodium supplementation during ultramarathons remains strong: findings from the Ultrarunners Longitudinal TRAcking (ULTRA) study. Applied Physiology, Nutrition, and Metabolism, 2020.
Survey1,152 ultrarunners: two-thirds wanted sodium supplements at races, believing they prevent low blood sodium and cramps; the evidence says extra sodium is generally not needed.
doi.org/10.1139/apnm-2019-0238 - [5]
Chen Y, Zhao X, Li X, et al. Nutritional status and practices among Chinese marathon runners: data from the China marathon nutrition survey (CMNS). Journal of the International Society of Sports Nutrition, 2025.
Survey5,668 marathon runners surveyed in 2024: among those who used supplements, more than 90% used energy gels and 54.4% used salt tablets.
doi.org/10.1080/15502783.2025.2533504 - [6]
Del Coso J, González-Millán C, Salinero JJ, et al. Effects of oral salt supplementation on physical performance during a half-ironman: a randomized controlled trial. Scandinavian Journal of Medicine and Science in Sports, 2016.
Randomised controlled trial26 triathletes: the salt-capsule group finished a half-ironman faster, with higher blood sodium afterwards, than the control group.
doi.org/10.1111/sms.12427 - [7]
Hew-Butler T, Loi V, Pani A, Rosner MH Exercise-associated hyponatremia: 2017 update. Frontiers in Medicine, 2017.
Expert reviewDrinking beyond thirst, together with the hormone vasopressin, is the most common cause of low blood sodium during exercise.
doi.org/10.3389/fmed.2017.00021 - [8]
Namineni N, Potok OA, Ix JH, et al. Marathon runners' knowledge and strategies for hydration. Clinical Journal of Sport Medicine, 2022.
Survey210 marathon runners: fewer than 5% named drinking to thirst, the 2015 consensus guidance. Slower and first-time runners knew least about low blood sodium.
doi.org/10.1097/JSM.0000000000000990 - [9]
Hew-Butler T, Rosner MH, Fowkes-Godek S, et al. Statement of the Third International Exercise-Associated Hyponatremia Consensus Development Conference, Carlsbad, California, 2015. Clinical Journal of Sport Medicine, 2015.
Consensus statementThe 2015 international consensus on exercise-associated low blood sodium: drinking beyond thirst is the main cause, and it advises drinking to thirst.
doi.org/10.1097/JSM.0000000000000221 - [10]
NHS Salt in your diet. NHS, 2026.
RegulatorAdults should have no more than 6 g of salt a day; eating too much salt can cause high blood pressure.
www.nhs.uk/live-well/eat-well/food-types/salt-in-your-diet/ - [11]
World Anti-Doping Agency The Prohibited List. World Anti-Doping Agency, 2026.
RegulatorThe substances and methods prohibited in sport. Sodium and other electrolytes are not on it.
www.wada-ama.org/en/prohibited-list - [12]
Maughan RJ, Burke LM, Dvorak J, et al. IOC consensus statement: dietary supplements and the high-performance athlete. British Journal of Sports Medicine, 2018.
Consensus statementOnly a few performance supplements, including caffeine, creatine, nitrate and sodium bicarbonate, have good evidence. Responses vary between people, and contamination is a known anti-doping risk.
doi.org/10.1136/bjsports-2018-099027 - [13]
Schwellnus MP Cause of exercise associated muscle cramps (EAMC): altered neuromuscular control, dehydration or electrolyte depletion?. British Journal of Sports Medicine, 2009.
Expert reviewThe electrolyte-loss explanation for cramps rests mainly on anecdote and case reports; four cohort studies don't support it, and evidence points to altered neuromuscular control.
doi.org/10.1136/bjsm.2008.050401
Who wrote and reviewed this
Written by Grant MacMillan, Editor, RunV. Not yet reviewed by an expert.
Last checked against its references . Next review due . How pages are reviewed · How we grade research
Research alerts
Train smarter
Most gains come from consistent training. See how RunV builds your plan.
See how RunV builds your plan