# Drinking water and hydration in the sauna

Source: https://saunabenefits.uk/how-to/hydration/
Author: Kit Ellery · Updated 2026-11-04

**Short answer:** Most people sweat around half a kilo in a sauna session, more in long or very hot sessions. Drink a glass of water before you go in and another one or two afterwards, and more if you do several rounds or have just exercised. Plain water is enough for most people; avoid alcohol, which dehydrates you and raises the risks.

## How much fluid do you lose?

Around half a kilo in a typical session, which is roughly a pint of sweat. You lose more if the sauna is hotter or more humid, if you stay longer or do several rounds, and if you're larger. A Polish study of 674 students who spent two 10-minute spells in a dry sauna found that heavier people lost the most weight through sweat, and warned they should take particular care to replace fluids.

Weighing yourself before and after is a simple way to see how much you lose. Every kilo lost is about a litre of fluid to replace.

## How much should you drink?

- **Before:** a glass of water (about 250 ml) in the hour before.
- **During:** sips from a water bottle if you're doing several rounds.
- **After:** one or two glasses, and more after exercise or a long session. Keep going until your pee is pale yellow.

## Water, electrolytes or something else?

Plain water is fine for most people. Sweat contains sodium, and long, heavy sweating can deplete it, so after several rounds, a hard workout or a hot day an electrolyte drink or a salty snack can help. Avoid drinking very large amounts of plain water quickly after heavy sweating.

## What about alcohol?

Don't drink before or during a sauna. Alcohol makes you lose more fluid, lowers blood pressure further and dulls the warning signs of overheating. In Finland, about half of the people who died in a sauna were under the influence of alcohol. See [alcohol and saunas](/safety/alcohol/).

## Who needs to be extra careful?

- People taking diuretics (water tablets) or other medicines that affect fluid balance.
- People with kidney disease or heart failure who have been told to limit fluids: ask your doctor how to balance the two.
- Older adults, who may feel less thirsty.
- Anyone who has been ill with vomiting or diarrhoea.

## Frequently asked questions

### Do I need electrolyte drinks after a sauna?

Usually not. Sweat contains salt, but a normal meal replaces it. Electrolyte drinks can help after very long sessions, heavy exercise in the heat or if you feel crampy, but water and food are enough for most people.

### Can I drink water in the sauna?

Yes. Many venues allow a water bottle on the bench. Small sips during longer sessions are fine.

### What are the signs of dehydration?

The NHS lists feeling thirsty, dark yellow and strong-smelling pee, peeing less often, feeling dizzy or light-headed, feeling tired, and a dry mouth, lips and eyes.

## References

1. [Podstawski R et al. Sauna-induced body mass loss in young sedentary women and men. The Scientific World Journal, 2014.](https://pubmed.ncbi.nlm.nih.gov/25614882/)
2. [Hannuksela ML, Ellahham S. Benefits and risks of sauna bathing. American Journal of Medicine, 2001.](https://pubmed.ncbi.nlm.nih.gov/11165553/)
3. [NHS. Dehydration.](https://www.nhs.uk/conditions/dehydration/)
4. [Kenttämies A, Karkola K. Death in sauna. Journal of Forensic Sciences, 2008.](https://pubmed.ncbi.nlm.nih.gov/18471223/)