Do Athletes Actually Need Electrolytes?
- Shrey Aggarwal
- Aug 11
- 7 min read
Updated: Aug 13
A club runner came to me last year with a shoebox of sachets. Four brands, three flavours, one of them bought in an airport in Dubai because the packet looked serious. She was taking two tabs before every session, including 40-minute easy runs in an air-conditioned gym. Her actual sodium loss on those runs was somewhere around a quarter of what she was drinking back.
Most athletes training under an hour don't need electrolyte products; normal food and water cover their losses. Electrolytes earn their place in long sessions (90+ minutes), heavy sweating, hot conditions, or multiple sessions a day. Sodium is the one that matters most; the rest are marketing more often than need.
That's the whole answer. The rest of this is how to work out which side of the line you're on.
Quick Overview
Do athletes need electrolytes for every session?
No. For exercise under about an hour, there's little evidence of any physiological or performance difference between a carbohydrate-electrolyte drink and plain water (Sawka et al., Med Sci Sports Exerc, 2007). You finish a 45-minute tempo run slightly down on fluid and sodium, you eat a meal, and the deficit closes on its own. Food is an electrolyte product. A bowl of dal with rice, a cheese sandwich, miso soup, a plate of pasta with sauce, all of these carry more sodium than most tabs on the market.
Two thresholds sit in the guidance, and they're worth separating. One hour is where the evidence stops showing any difference between an electrolyte drink and water. Two hours is where ACSM says sodium should be added during exercise, alongside sweat rates above 1.2 litres an hour or known salty sweat (Thomas et al., Med Sci Sports Exerc, 2016). The 90-minute mark I use in practice sits between the two, and it's my clinical judgement rather than a position-stand number. In heat and humidity I start seeing sodium replacement change how athletes feel and finish well before the two-hour line. In cool conditions, ACSM's threshold is the better guide.
Where this goes wrong is habit. Athletes buy electrolytes for a marathon build, then keep taking them through the off-season on 30-minute jogs. Nothing bad happens. It's just money spent solving a problem that isn't there, and it can mask the actual issue, which is usually that the athlete isn't eating enough carbohydrate.
How much sodium do you actually lose in sweat?
Enough that the answer is different for every athlete in the room. Sweat rates during exercise run from 0.3 to 2.4 litres an hour depending on intensity, duration, fitness, heat acclimatisation and conditions, and the average sodium concentration in sweat sits around 50 mmol/L, roughly 1g per litre (about 34 fl oz), described in the guidance itself as highly variable (Thomas et al., Med Sci Sports Exerc, 2016). Multiply the two ends together and hourly sodium loss spans from around 300mg to well over 2,000mg. That spread is why blanket dosing fails. Two players on the same hockey pitch in Bhubaneswar or Amstelveen, same session, same conditions, can sit at opposite ends of it.
Nothing about your build or fitness tells you where you sit. A lean, well-trained athlete can be a heavy salt loser and a bigger, slower one can be dilute. Salty-sweat status is largely genetic and reasonably stable in adults, which is at least useful for planning: once you know, it's a fixed number rather than something to re-guess every race. The visible clues are real but rough, and they only flag the extreme end. White crusting on kit and skin, stinging eyes, a distinctly salty taste on the lip.
Heat and humidity move the fluid side of that equation hard, which is why the same athlete needs a different plan for a monsoon-season session in Mumbai, a dry summer race in Arizona and a cool morning in Rotterdam. The practical way to find your own number is weighing yourself before and after a session, accounting for what you drank. A loss of 1kg (2.2lb) of bodyweight represents roughly 1 litre of sweat.
Do electrolytes prevent cramp?
Mostly not, and this is the claim I'd most like to see retired from packaging. ACSM states plainly that skeletal muscle cramps are typically caused by muscle fatigue (Thomas et al., Med Sci Sports Exerc, 2016). The mechanism evidence points the same way, toward an imbalance between muscle spindle drive and Golgi tendon organ inhibition at the alpha motor neuron rather than a dehydration or electrolyte deficit (Nelson & Churilla, Muscle Nerve, 2016). Athletes who cramp and athletes who don't frequently show no difference in blood electrolytes.
The practical read: if you cramp in the last twenty minutes of a match or the final climb of a long ride, the first suspects are pace, training load, and how much fuel you've taken on, not a missing salt tab. Sodium may still help a specific subset of heavy, salty sweaters in long, hot events, and ACSM notes those athletes may be at greater risk, particularly when they aren't acclimatised. It isn't the general answer, and treating it as one means the real cause goes unaddressed for months.
There's a second reason sodium matters in long events, and it has nothing to do with cramp. Drinking large volumes of fluid over many hours in excess of sweat and urine losses is the primary cause of exercise-associated hyponatremia, and it's compounded when the fluid used is low in sodium (Hew-Butler et al., Clin J Sport Med, 2015). This is a real risk in marathons, ultras and long-course triathlon, and it's the strongest argument for sodium in a bottle rather than a bare one. Recreational athletes are more exposed than elites here, because their sweat rates are lower while their belief in the need to drink is often higher.
When electrolytes genuinely earn their place
Four conditions, and you generally need at least one of them. Sessions past 90 minutes, where losses accumulate faster than the next meal can replace them. Heat and humidity, which push sweat rates up regardless of intensity, whether that's a June afternoon in Chennai, a Queensland summer or an unusually warm week in Manchester. Two or three sessions in a day, common in tournament sport and pre-season, where you never get a full recovery period between efforts. And known salty-sweat status, verified by a patch test rather than by how your face feels.
For a long session, sodium in the range of 500 to 700mg per litre of fluid is a sensible starting point (Sawka et al., Med Sci Sports Exerc, 2007), moving higher for heavy salt losers in heat. Fluid itself wants to land around 0.4 to 0.8 litres an hour for most athletes and events, adjusted to your own tolerance and drinking opportunities. Carbohydrate matters more than sodium for most sessions in this bracket, which is why I'd rather see an athlete get their carbohydrate intake per hour right first and treat sodium as the second layer.
Potassium, magnesium and calcium: do they matter?
They matter physiologically. They rarely matter as a supplement decision. Sweat potassium sits at a fraction of sodium concentration, and normal eating replaces it easily; a banana, a handful of dates, potatoes, spinach, beans. Calcium and magnesium losses in sweat are smaller still.
Magnesium is worth a separate word because it's marketed hard at athletes for cramp and sleep. On cramp, the trial evidence doesn't support it: pooled randomised trials show magnesium supplementation is unlikely to provide clinically meaningful cramp prevention at any dose tested (Garrison et al., Cochrane Database Syst Rev, 2020). That work covers idiopathic and pregnancy-associated cramps rather than exercise cramps specifically, which the reviewers flag as still needing trials, so read it as no reason to expect a benefit rather than a closed case.
On testing, if there's genuine reason to check status, that's an RBC magnesium test. Under 1% of body magnesium sits in blood, and tissue stores can be depleted while serum reads normal (Costello & Nielsen, Curr Opin Clin Nutr Metab Care, 2017). Deficiency is worth correcting where it exists. Adding magnesium to a drink mix to prevent cramp is not. So when a label lists five minerals, four of them are there for the label. Sodium is doing the work.
Fueletics Perspective
I've had more athletes fix a hydration problem by eating properly than by buying a better product. Under-fuelling and dehydration produce overlapping symptoms, and the sachet is the easier thing to change, so it gets changed first. Then six months go by.
My working order is this. Establish whether the session is long enough, hot enough, or repeated enough to matter. If it is, sort carbohydrates first, then add sodium at a dose scaled to your own sweat, not to the scoop size on the tub. If none of those conditions apply, drink water, eat your meals, and spend the money on something that moves the needle.
Two of those numbers are individual, sweat rate and sweat sodium, and the published ranges are wide enough that generic dosing produces both under-replacement and pointless over-replacement inside the same training group. If you want yours worked out against your actual sessions and climate, start with a Fueletics assessment.
FAQs
Do I need electrolytes for a 5K or a gym session?
No. Under an hour, water and your normal meals cover it (Sawka et al., Med Sci Sports Exerc, 2007). This holds in heat too, though you'll want more fluid.
Are electrolyte drinks better than water?
For long sessions, in heat, or across multiple sessions a day, yes. ACSM puts the trigger at exercise beyond two hours, sweat rates above 1.2 litres an hour, or known salty sweat. Below that, no measurable performance difference has been shown.
Can you take too many electrolytes?
You can. Excess sodium with limited fluid causes gut distress and nausea mid-session, and high-sodium products offer nothing to an athlete whose losses are already replaced by food. Athletes with high blood pressure or kidney conditions should check with their doctor before adding sodium deliberately.
Do electrolytes help with cramp?
Rarely as the primary fix. Muscle fatigue is the typical cause (Thomas et al., Med Sci Sports Exerc, 2016; Nelson & Churilla, Muscle Nerve, 2016). Look at pacing, training load and fuelling first.
Research References
Sawka MN, Burke LM, Eichner ER, et al. American College of Sports Medicine Position Stand: Exercise and Fluid Replacement. Med Sci Sports Exerc, 2007;39(2):377-390. DOI: 10.1249/mss.0b013e31802ca597
Thomas DT, Erdman KA, Burke LM. American College of Sports Medicine Joint Position Statement: Nutrition and Athletic Performance. Med Sci Sports Exerc, 2016;48(3):543-568. DOI: 10.1249/MSS.0000000000000852
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. DOI: 10.1097/JSM.0000000000000221
Nelson NL, Churilla JR. A narrative review of exercise-associated muscle cramps: factors that contribute to neuromuscular fatigue and management implications. Muscle Nerve, 2016;54(2):177-185. DOI: 10.1002/mus.25176
Garrison SR, Korownyk CS, Kolber MR, et al. Magnesium for skeletal muscle cramps. Cochrane Database Syst Rev, 2020;9:CD009402. DOI: 10.1002/14651858.CD009402.pub3
Costello RB, Nielsen F. Interpreting magnesium status to enhance clinical care: key indicators. Curr Opin Clin Nutr Metab Care, 2017;20(6):504-511. DOI: 10.1097/MCO.0000000000000410
