Electrolytes: when you actually need them (and when water is enough)

• 8 min read
• Updated: October 29, 2026
• 6 sources cited

You need electrolytes on top of water mainly when you sweat a lot for a long time: long sessions, heat, several workouts in one day or hours of hard physical work. For a typical gym session or a 45-minute run, water and your normal meals are usually enough. The electrolyte that matters most in sweat is sodium, and the amount you lose varies a lot from person to person.

Electrolytes: the essentials in 30 seconds

What you lose in sweat when you exercise

Sweat is mostly water, but it carries electrolytes with it, and sodium is the main one. A 2023 modelling study in the European Journal of Sport Science worked with realistic ranges for athletes: sweat rates of 0.5 to 2.5 liters per hour and sweat sodium of 20 to 80 mmol per liter. Converted to milligrams, that is roughly 460 to 1,840 mg of sodium per liter of sweat (1 mmol of sodium = 23 mg).

The spread is huge. EFSA's sodium opinion notes that sweat sodium varies widely, depending on how much sodium you eat, how much you sweat, your hydration and how acclimatized you are to the heat. Potassium is a different story: the NIH Office of Dietary Supplements points out that only a very small amount is lost in sweat.

When electrolytes make sense

The American College of Sports Medicine (ACSM) position stand says that during exercise, drinks with electrolytes and carbohydrates "can provide benefits over water alone under certain circumstances." In practice, those circumstances look like this:

• Long efforts: sessions of well over an hour, long rides, trail runs, hikes.
• Heat and humidity: you sweat more, so you lose more fluid and sodium.
• Heavy or salty sweaters: clothes soaked through or white salt marks on your cap.
• Two sessions a day or tournaments: little time to recover between efforts.
• Hard physical jobs in hot environments.

Even then, the numbers are less dramatic than ads suggest. The 2023 model found that replacing sodium during a soccer match or an elite marathon was unnecessary in every realistic scenario. Targeted sodium replacement only appeared necessary in very long events, like a 160 km ultramarathon, combined with drinking most of what you sweat and salty sweat (40 mmol/L or more).

When water is enough

For a typical strength session, a class or a run under about an hour, water does the job. Your meals supply sodium and potassium, and your kidneys adjust losses when intake is low, as EFSA describes. Drinking electrolyte mixes "just in case" every day mostly adds sodium you probably already get from food, plus sweeteners or sugar depending on the product.

Sodium and potassium: the reference numbers

No upper limit doesn't mean "the more the better." EFSA set 2.0 g of sodium a day after reviewing the evidence on sodium intake, blood pressure and cardiovascular disease. For potassium, the NIH notes that very large supplement doses can exceed what the kidneys can excrete, and that many supplements contain no more than 99 mg per serving. If a product gives you a daily maximum on the label, treat it as a hard ceiling.

Electrolytes: what EU rules allow us to say

We're a European company, and in the EU a food supplement can only use health claims the European Commission has authorized, with their conditions of use. For the minerals in electrolyte powders, these apply:

"Magnesium contributes to electrolyte balance." Only for products that provide at least 15% of the nutrient reference value (56.25 mg of magnesium) per daily portion.

EU Regulation 432/2012

"Potassium contributes to normal muscle function." Only for products that provide at least 15% of the nutrient reference value (300 mg of potassium) per daily portion.

EU Regulation 432/2012

There are also two claims for carbohydrate-electrolyte solutions, such as "Carbohydrate-electrolyte solutions enhance the absorption of water during physical exercise." Their conditions are strict: 80–350 kcal per liter from carbohydrates, 460–1,150 mg of sodium per liter (20–50 mmol/L) and a set osmolality. Sugar-free electrolyte powders don't meet them, so they can't use those claims. Sodium on its own has no authorized function claim.

How to use electrolytes: a simple plan

1. Weigh yourself before and after a typical hard session, without sweaty clothes. Every kg (2.2 lb) lost is about one liter of sweat. The ACSM uses a loss of more than 2% of body weight as the line to avoid.
2. Look at the context: under an hour and cool weather, water. Long, hot or double sessions, consider adding sodium.
3. Afterwards, the ACSM suggests drinking about 1.5 L of fluid per kg lost, with your meal or a salty snack covering most of the sodium.
4. Follow the label: mix with the stated amount of water and don't exceed the daily maximum.

How to read an electrolyte label

• Look for mg of sodium per serving and work out mg per liter once mixed. If a brand doesn't list it, you can't compare.
• Check potassium and magnesium per serving and the daily maximum.
• Check sugar and caffeine: some "hydration" mixes are really energy drinks.
• Compare price per serving, not per tub.

FAQ: electrolytes

Do I need electrolytes if I drink a lot of water?

Usually not. If you eat normally and train under about an hour, water is enough. Electrolytes become relevant with long, sweaty sessions, heat or several workouts a day.

Is it OK to drink electrolytes every day?

For most healthy adults an occasional serving within the label limits isn't a problem, but daily use without heavy sweating mainly adds sodium. EFSA considers 2.0 g of sodium a day a safe and adequate intake for adults.

When should I take electrolytes: before, during or after a workout?

During long or hot sessions and afterwards, alongside the fluid you need to replace what you lost. Before a short workout they add little.

How much sodium do you lose in sweat?

It varies a lot. Research uses ranges of about 460 to 1,840 mg of sodium per liter of sweat, and sweat rates of 0.5 to 2.5 liters per hour.

Are electrolyte drinks good for a hangover or when you're sick?

For vomiting or diarrhea, oral rehydration solutions from the pharmacy are a different, specific product. Ask a pharmacist or doctor, especially for children, older adults or if it lasts more than a day or two.

Can people with high blood pressure take electrolytes?

Check with your doctor first. Most electrolyte mixes are built around sodium, and some contain potassium, which matters if you take certain blood pressure medicines.

Sources

• EU Regulation 432/2012 — authorized health claims (magnesium, potassium, carbohydrate-electrolyte solutions)
• EFSA NDA Panel — Dietary reference values for sodium (EFSA Journal, 2019)
• EFSA — Dietary reference values: advice on potassium (2016)
• NIH Office of Dietary Supplements — Potassium fact sheet for health professionals
• American College of Sports Medicine position stand: Exercise and fluid replacement (Med Sci Sports Exerc, 2007)
• McCubbin AJ — Modelling sodium requirements of athletes across a variety of exercise scenarios (Eur J Sport Sci, 2023)