Electrolytes and sodium in endurance sports – how much and when?

Short answer: The need for sodium in endurance sports is not the same for everyone. It depends primarily on how much you sweat, how salty your sweat is, how long the performance lasts, and the conditions in which you are moving. Therefore, you should not use a single "sodium X mg per hour" figure that fits everyone as a starting point.

Which electrolytes are lost in sweat?

Water and electrolytes are lost through sweat. Sodium and chloride are the most important in terms of quantity, but smaller amounts of substances such as potassium, magnesium, and calcium are also lost.

In endurance sports, practical attention is usually focused particularly on fluid and sodium, as their losses can be significant during long and hot performances.

Sodium loss varies significantly

Studies have observed significant individual variation in both sweat rate and sweat sodium concentration. This variation is explained by factors such as exercise intensity, environment, body size, heat acclimatization, and individual characteristics.

This means that two cyclists of the same size can lose completely different amounts of fluid and sodium in the same race. The needs of the same athlete can also change depending on weather conditions and pace.

When is an electrolyte drink most beneficial?

• during long-duration training or competition lasting several hours
• in hot or humid conditions
• if you sweat a lot
• if visible salt crystals remain on your clothes or skin
• if you drink large amounts of fluid during exercise
• on long event days where hydration continues for hours

For short workouts in cool conditions, a normal diet and water may be perfectly sufficient. There is no need to automatically use an electrolyte drink for every workout.

How much sodium per hour?

Instead of a single fixed number, it is better to think in terms of estimated loss and practical replacement. Research data has shown multiple differences in athletes' sweat sodium concentrations and sodium losses.

If you do not know your own sweat sodium concentration, you cannot calculate your exact sodium loss. In this case, a more sensible goal is to practice an effective hydration strategy, monitor how you feel, and avoid both significantly insufficient and excessive drinking.

If the goal is a precise individual plan for, for example, a long race in hot weather, a properly conducted sweat test can provide useful additional information.

How can you estimate your sweat rate?

A simple field assessment can be done by weighing yourself before and after a workout. Also, estimate the amount of fluid consumed and any urine produced.

Sweat rate (l/h) ≈ (weight before − weight after + fluid consumed in liters − urine in liters) / exercise time in hours.

For example, if your weight drops by 0.7 kg during a one-hour run and you drink 0.5 liters, the estimated sweat rate is approximately 1.2 l/h. It is worth repeating the measurement under similar conditions more than once.

The formula is a practical estimate, not a laboratory measurement.

Can you estimate sweat saltiness without a test?

Salt crystals on the skin or clothes, stinging sweat in the eyes, and very salty sweat stains may indicate significant sodium loss, but you cannot deduce an exact mg/l value based on them. If precision is important, a proper measurement is needed.

Electrolytes do not make overhydration safe

This is an important safety issue. Drinking too much fluid during a long performance can dilute blood sodium levels and predispose one to exercise-associated hyponatremia. Adding sodium to the drink does not eliminate the risk of excessive drinking.

A good practical principle is to avoid drinking in such a way that your weight rises above the starting level during the performance. Drinking should be adapted to your thirst, sweating, conditions, and a pre-practiced plan.

Sodium or all electrolytes?

Products often speak of "electrolytes," but in long-duration endurance sports, sodium is usually the most important electrolyte lost in sweat in terms of quantity. A product containing magnesium or potassium is therefore not automatically a better hydration drink if it contains very little sodium.

When comparing products, it is worth looking at the amount of sodium or salt per serving and per prepared liter of drink.

Electrolyte drink or sports drink?

An electrolyte drink can be almost carbohydrate-free and focus on hydration. A sports drink usually also contains carbohydrates and thus acts as an energy source at the same time. The choice depends on where you get your carbohydrates during the performance.

Read a more detailed comparison: Sports drink or electrolyte drink – what is the difference?

Choose this way in practice

• Light workout under about an hour in the cool: an electrolyte supplement is usually not necessary.
• Long workout or competition: hydration and sodium intake should be planned as part of your refueling.
• Hot weather or heavy sweating: the importance of electrolytes increases.
• You get carbohydrates from gels or food: a low-carbohydrate electrolyte drink can be practical.
• You want energy and liquid from the same bottle: a carbohydrate-containing sports drink may be better.

Frequently asked questions

Do I need electrolytes for a one-hour run?

Often no, if conditions are cool and your diet is normal. Heat and exceptionally heavy sweating can change the situation.

Is more sodium always better?

No. The need is individual, and the amount of sodium in the product must be proportional to the duration of the performance, the amount of fluid consumed, and estimated losses.

Can you take too many electrolytes?

Yes. You should not use unnecessarily large amounts. Especially illnesses, medications, or individual health problems can affect fluid and electrolyte balance.

Sources

• Baker 2017: Sweating Rate and Sweat Sodium Concentration in Athletes
• Barnes et al. 2019: sweating rate, sweat sodium concentration and sodium loss in athletes
• International Exercise-Associated Hyponatremia Consensus
• Exercise-associated hyponatremia: pathophysiology and treatment, 2026

Updated 15.10.2026. The article provides general sports nutrition information and does not replace individual medical guidance.

Plan your fueling: Build a carbohydrate plan from sports drinks and other energy sources. The Energy Calculator shows estimated carbohydrate and sodium amounts for product combinations; its sodium figures are not individualized salt-intake recommendations. Open the FuturePeaks Energy Calculator.