Electrolytes during endurance sports: how much salt do you really need
TL;DR — You lose roughly 200 to 1,700 mg of sodium per liter through sweat. That is a massive range, so general salt advice doesn't mean much. The real risk during long exercise is not drinking too little, but too much water without salt. Put your sodium where it belongs: in your water bottle, not in a separate pill afterward. Guideline for over 90 minutes: 500 to 800 ml of sports drink per hour with 500 to 700 mg of sodium per liter, plus 1 to 2 bars per hour for your carbohydrates. Drink to thirst, not to a schedule.
Electrolytes during endurance sports are the minerals that manage your fluid balance, muscle contraction, and nerve conduction. Sodium is the most important of these. If you lose a lot of it and only replenish with water, you dilute your blood instead of replenishing it. That is not a theoretical risk: it is the most well-documented error in endurance sports nutrition. In the complete guide to energy bars and cycling, I cover the carbohydrate side. This piece is about the salt side, and how the two belong together.
What electrolytes do during exercise
Electrolytes are minerals that dissolve in your body fluids and carry an electrical charge. For an endurance athlete, there are four that count: sodium, chloride, potassium, and magnesium. They determine how much fluid stays in and around your cells, they transmit the signal that makes your muscle contract, and they keep your heart rhythm stable.
Of those four, sodium does the heavy lifting. It is the mineral you lose in the greatest quantity through sweat, and it is the mineral that determines whether the fluid you drink actually ends up in your blood or just passes through. Sweat is not pure water. It contains salt, and that salt leaves the building while you ride or run.
Above 60 to 90 minutes of exercise, that loss stops being negligible. From that point on, your electrolyte balance is no longer a detail in your nutrition plan. It is the condition under which the rest of your plan works.
How much sodium you actually lose per hour
The honest summary: no one knows that for you. The range between athletes is larger than with just about any other variable in sports nutrition. Sweat contains roughly 200 to 1,700 mg of sodium per liter, and where you fall in that range is largely genetically determined.
Do the math. If you sweat a liter per hour and are on the low end, you lose about 250 mg of sodium per hour. If you are on the high end and sweat a liter and a half in the heat, you are over 2,000 mg per hour. That is a difference of a factor of eight between two riders riding next to each other. Any advice that gives one number for everyone ignores that.
What drives up your sodium loss: high temperature and humidity, high intensity, and the fact that you aren't yet used to heat. Anyone who just ends up in a heatwave from a cold winter loses structurally more salt than someone who has been acclimated for two weeks.
You don't need a lab test to estimate your own side of the range. White salt rings on your water bottle, your sunglasses, or your black jersey after a long ride are a useful indicator. If you see those consistently, you are on the high end and need more sodium than the average advice. If you never see anything, you don't need to exaggerate.
Water without salt is the real risk
The sports world has been shouting "drink enough" for twenty years. That advice has created a problem bigger than the one it solved. Hyponatremia means the sodium level in your blood drops below 135 millimoles per liter. In athletes, the cause is almost never that you didn't get enough salt in. The cause is that you drank too much fluid.
The international consensus statement on exercise-associated hyponatremia is explicit about this: excessive fluid intake is the dominant cause, and drinking to thirst rather than on a fixed schedule is the most important preventive measure. So it's not just about what is in your bottle, but also about how much you guzzle.
The risk is highest with a specific profile: athletes who go relatively slowly and thus have plenty of time to drink, athletes who drink by the clock instead of by feel, athletes who use exclusively water, and efforts over four hours. It's not just an ultra-problem. It also occurs in regular marathons and half-triathlons.
What makes it treacherous is that the early signals look exactly like what you expect during heavy exertion: nausea, headache, a bloated feeling. In serious cases, it can lead to confusion and loss of consciousness. This article is informative. If you have these symptoms during or after exercise, call a doctor, not a coach.
Sodium belongs in your water bottle, not in a pill afterward
This is where most athletes go wrong. They treat electrolytes as a separate product that they take when something goes wrong. Salt should not be an emergency solution. It should be dissolved in the fluid you drink throughout the entire ride.
There is a physiological reason for this. Sodium and glucose are pulled into your small intestine by the same transport channel. If you take them together, the absorption of both goes more smoothly, and it pulls the fluid along with it. A meta-analysis of 26 studies on combined carbohydrate and electrolyte intake found that that combination significantly extended the time to exhaustion. Not the salt separately, not the sugar separately. The combination.
That is why my breakdown looks like this. The sports drink is your main source: 500 to 800 ml per hour, with 6 to 8% carbohydrates and 500 to 700 mg of sodium per liter. That gives you 30 to 60 g of carbs and 300 to 550 mg of sodium per hour, without having to do anything extra. On top of that, you eat 1 to 2 bars per hour for the rest of your carbohydrates. In heat, on a long day, or if you are a pronounced salt sweater, you can go to 1,000 mg of sodium per hour, and only then does a salt tablet come into play as a supplement to your drink.
The bar does one thing in this system: provide fuel. Not salt. Anyone who builds their sodium plan on solid food is building it on the wrong component. If you want to know when solid food wins over liquid, read energy bar versus energy gel: when what.
Potassium and magnesium: useful, not leading roles
Potassium is mainly inside your cells and plays a role in muscle contraction and heart rhythm. You also lose it through sweat, but in much smaller quantities than sodium, and your body handles that loss better. You lose magnesium in even smaller quantities, somewhere around 4 to 15 mg per liter of sweat.
That doesn't mean they don't count. It means the order is fixed. If your sodium is not correct, you won't solve anything by adding magnesium. First, replenish the mineral that you are losing by the hundreds of milligrams per hour, and treat potassium and magnesium as the final touch of a good daily diet instead of as a race product.
That also applies to cramps, by the way. Cramps during exercise are often blamed on a magnesium deficiency, but the evidence for that is thin. Fatigue of the muscle itself and a disturbed sodium and fluid balance are more likely suspects.
What's where
Before you build your plan, you need to know what each form actually provides. Many athletes overestimate how much salt is in solid food and underestimate how much should be in their drink. The same fallacy applies to sugar: pure sugar provides energy but nothing else, and I explained that difference in fruit energy bar versus candy.
| Form | Sodium per serving | Carbs per serving | Role in your plan |
|---|---|---|---|
| Sports drink (500 ml) | 250 to 350 mg | 30 to 40 g | Main source for fluid, salt, and base carbs |
| Energy gel (40 g) | 50 to 200 mg | 22 to 27 g | Quick peak in the finale, not a salt source |
| Fruit performance bar (25 g) | Negligible | 20 g | Solid fuel, 1 to 2 per hour |
| Salt tablet (1 piece) | 300 to 1,000 mg | 0 to 5 g | Supplement in heat or for salt sweaters |
| Water (500 ml) | 0 mg | 0 g | Fine up to 60 minutes, then too little |
The lesson from that table: you get your salt from what you drink. Anyone who builds their entire fueling strategy on gels will structurally come up short on sodium during long efforts. That is one of the reasons why more and more cyclists are trading the gel for a clean label fruit energy bar and letting their drink do the salt work.
How to recognize it during the ride
The distinction you need to be able to make is between having drunk too little and having drunk too much. They don't feel the same, but they are constantly confused.
Too little fluid gives you thirst, a dry mouth, dark urine, and a heart rate that is higher than your power output justifies. Too much fluid without salt actually doesn't give you thirst, because you just drank. What you do get: a headache that comes on after drinking, nausea for no apparent reason, a bloated feeling, swollen fingers making your ring feel tight, and a loss of performance that doesn't match how hard you've been riding.
That distinction is important, because the reflex in both cases is the same: take another sip. In the second case, you make it worse with that. These remain signal descriptions for informational purposes. Serious complaints belong to a doctor, not self-diagnosis on the side of the road.
Your protocol per hour
This is what it looks like when you make it practical.
Up to 60 minutes. Water suffices. You don't need to plan anything.
60 to 90 minutes. One bottle of sports drink. In warm weather, start with sodium in your drink here instead of pure water.
90 minutes to 3 hours. 500 to 800 ml of sports drink per hour with 500 to 700 mg of sodium per liter, plus 1 to 2 bars per hour. Together, you are then at 50 to 80 g of carbs and 300 to 550 mg of sodium per hour. Drink to thirst, not to the clock.
More than 3 hours. Same basis, but stick to it from the first hour instead of from the moment you feel it. In heat or if you are a salt sweater, increase to 700 to 1,000 mg of sodium per hour via a stronger drink or an additional salt tablet. Eat every hour, even if you don't feel anything yet.
Test this in training. Every stomach reacts differently to concentration and volume, and a race weekend is the worst imaginable place to find out that your drink is too strong. Anyone looking for something that keeps working on the bike without sticky mess will find the solid part of this system in the ideal snack for your bike ride.
What it boils down to
Salt is not a supplement you take on the side. It is the component that makes your fluid work and lets your carbohydrates be absorbed. Put it in your water bottle, keep your drink and your bars separate in terms of their roles, drink to thirst and not to a schedule, and test everything before you use it in a race.
No gel. No brick. Fuel during exertion. Fuel your flight.
Scientific foundation
The international consensus statement on exercise-associated hyponatremia (Hew-Butler and colleagues, Clinical Journal of Sport Medicine, 2015) defines hyponatremia in athletes as serum sodium below 135 mmol/L during or up to 24 hours after exercise, and identifies excessive fluid intake as the dominant cause. The recommendation is to drink to thirst rather than on a fixed schedule.
Veniamakis and colleagues (International Journal of Environmental Research and Public Health, 2022) mapped sodium requirements in endurance and ultra-endurance sports and show the large individual variation in sweat sodium, with the associated consequences for both too low and too high intake.
Bravo-Sánchez and colleagues (Applied Sciences, 2026) aggregated 26 studies on combined carbohydrate and electrolyte supplementation. The meta-analysis found a significant increase in time to exhaustion and blood glucose levels with the combination, which supports the principle that carbs and electrolytes belong together rather than as separate choices.
Rowlands and colleagues (Sports Medicine, 2022) analyzed 28 studies on the influence of drink concentration on blood volume during continuous exercise and show that the sugar concentration of your drink helps determine how well you stay hydrated.
Sources
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;25(4):303-320. doi:10.1097/JSM.0000000000000221
Veniamakis E, Kaplanis G, Voulgaris P, Nikolaidis PT. Effects of Sodium Intake on Health and Performance in Endurance and Ultra-Endurance Sports. International Journal of Environmental Research and Public Health, 2022;19(6):3651. doi:10.3390/ijerph19063651
Bravo-Sánchez A, Ramírez-delaCruz M, Sánchez-Infante J, Abián P, Abián-Vicén J. Carbohydrate and Electrolyte Supplementation Strategies to Enhance Sports Performance: A Systematic Review and Meta-Analysis. Applied Sciences, 2026;16(6):2967. doi:10.3390/app16062967
Rowlands DS, Kopetschny BH, Badenhorst CE. The Hydrating Effects of Hypertonic, Isotonic and Hypotonic Sports Drinks and Waters on Central Hydration During Continuous Exercise: A Systematic Meta-Analysis and Perspective. Sports Medicine, 2022;52(2):349-375. doi:10.1007/s40279-021-01558-y
Frequently asked questions
How much sodium do I need per hour during endurance sports?
For exercise over 90 minutes, 300 to 550 mg of sodium per hour is a workable starting point. You get that from 500 to 800 ml of sports drink per hour with 500 to 700 mg of sodium per liter. In heat, for efforts over three hours, or if you are a pronounced salt sweater, move toward 700 to 1,000 mg per hour. Under 60 minutes, you don't need to replenish anything.
What is hyponatremia and how does it develop in athletes?
Hyponatremia is a sodium level in the blood below 135 mmol/L. In athletes, it almost always occurs from drinking too much fluid, which causes the sodium in your blood to become diluted. The international consensus statement from 2015 calls excessive fluid intake the dominant cause. Symptoms are headache, nausea, a bloated feeling, and in serious cases confusion. The risk is greatest over four hours and for those who drink to a schedule instead of to thirst.
How much sodium do you lose per liter of sweat?
Roughly 200 to 1,700 mg per liter, with a strong individual variation that is largely genetically determined. Two riders next to each other can have a difference of a factor of eight. White salt rings on your clothing, sunglasses, or water bottle after a long ride indicate that you are on the high end and need more sodium than the average advice.
Can I get my electrolytes from an energy bar?
No. A fruit performance bar is a carbohydrate source, not a salt source. You get your sodium from what you drink. The setup that works: sports drink as the main source for fluid, salt, and base carbs, plus 1 to 2 bars per hour for the rest of your carbohydrates. In heat or with high salt loss, supplement with a salt tablet in your water bottle, not with more solid food.
Is drinking to thirst or to a schedule better?
To thirst. The consensus statement on exercise-associated hyponatremia calls drinking to thirst the most important preventive measure, because drinking to a fixed schedule more often leads to excessive fluid. That does not mean you can ignore sodium: above 90 minutes, salt in your drink remains necessary, regardless of how you plan your drinking moments.
Why do carbs work better when combined with sodium?
Sodium and glucose are absorbed in your small intestine via the same transport channel. When you take them together, the absorption of both is smoother, and it pulls fluid in with it. A meta-analysis of 26 studies from 2026 found that combined carbohydrate and electrolyte intake significantly increased the time to exhaustion compared to a placebo.
Does magnesium help against cramps while cycling?
The evidence for this is thin. You only lose 4 to 15 mg of magnesium per liter of sweat, compared to hundreds of milligrams of sodium. Cramps during exercise are more likely explained by muscle fatigue itself and a disrupted sodium and fluid balance. Get your sodium sorted first and treat magnesium as part of your daily diet rather than as a racing product.
