Do I always need an electrolyte drink?

No. On short, cool efforts, water is enough. Electrolytes, especially sodium, become useful on long efforts, in heat, or with heavy sweating.

How much should I drink per hour?

There's no universal figure: it depends on your sweat rate, the heat and the intensity. Drink to thirst, test on long runs, and weigh yourself before/after to estimate your losses.

Does salt prevent cramps?

Sodium plays a role in fluid balance and can help some runners, but cramps are multifactorial. Don't rely on salt alone.

Hydration7 min

Running hydration: water, sodium and electrolytes

Q: Can you drink too much water?

Yes. Drinking well past thirst, especially on long efforts, can dilute your blood sodium and cause hyponatremia — a rare but potentially serious condition. Sodium drinks, being hypotonic, don't always prevent it: the best protection is to drink to thirst rather than on principle.

Hydrating well while running isn't just 'drinking more'. The goal is to supply the right amount of fluid and, when useful, sodium and electrolytes, based on duration, heat and how much you sweat. On a short run in cool weather, water is enough; on a long effort or in heat, neglecting sodium can hurt both comfort and performance. This guide helps you tune your strategy.

Before: start well hydrated

Starting dehydrated handicaps the whole run. In the hours before, drink steadily rather than a big volume at once, and use clear urine as a simple check. In heat or before a long effort, adding a little sodium to your pre-run drink helps you retain fluid. There's no need to overload on water, though: drinking too much dilutes blood sodium and can be counterproductive.

During: water, sodium or electrolytes?

Under an hour in mild weather, plain water is usually enough. Beyond an hour, in heat or with heavy sweating, a drink containing sodium (and often carbs) becomes relevant: sodium supports fluid absorption and replaces sweat losses. Drink to thirst and intensity, in small regular sips, without drinking 'on principle'. Heavy sweaters and those with very salty sweat (white marks on the skin) have higher sodium needs. Beware the opposite excess: drinking well past thirst, especially on long efforts, can drop your blood sodium and cause hyponatremia — a rare but potentially serious condition. Sodium drinks, being hypotonic, don't always prevent it; the best protection is still to drink to thirst, not on principle.

After: rehydrate smartly

After a demanding run, rehydrate with water and a little sodium to replace what was lost, all the more if it was hot. A practical rule: drink gradually over the following hours rather than all at once. Weighing yourself before/after a long run gives you a sense of your real fluid losses.

Practical checklist

Steady hydration in the hours before
Plain water under 1 h in cool weather
Sodium (+ carbs) beyond 1 h, in heat or with heavy sweating
Drink to thirst and intensity, in small sips
Rehydrate with water + sodium after a hot or long effort

Common mistakes

Drinking huge amounts of plain water on a long effort, never any sodium
Starting already dehydrated and trying to 'catch up' during the run
Overloading on water to the point of diluting blood sodium
Copying another runner's strategy without accounting for your own sweat
Ignoring the heat, which sharply raises your needs

FAQ

Hydration6 min

Isotonic drink: what is it for?

An isotonic drink can combine hydration, electrolytes and carbs depending on the formulation and context.

Read the guide