How Much Sodium Do You Actually Lose in Sweat?
Most people think of sweat as water. It isn't. Every litre you sweat out takes a chunk of sodium with it, and for a lot of people that chunk is much bigger than whatever they're drinking to replace it.
Here are the real numbers, how to work out roughly where you sit, and why it matters.
The short answer
On average, people lose around 900–1,000mg of sodium per litre of sweat.
The range is huge, though. Large sweat-testing datasets show some people lose as little as ~200mg per litre, while others lose over 2,000mg per litre. That's roughly a tenfold difference between two people doing the same session side by side.
How much sodium you lose comes down to two numbers:
- Sweat rate: how many litres you sweat per hour
- Sweat sodium concentration: how salty each litre is
Multiply them together and you get your sodium loss per hour.
Sweat rate: how much you're losing
Sweat rates in active people commonly sit between 0.5 and 2.5 litres per hour, depending on:
- Intensity (a footy match vs a walk)
- Heat and humidity (January in Melbourne vs July)
- Body size
- Clothing and gear
- How heat-acclimatised you are
A rough guide:
| Activity | Typical sweat rate |
|---|---|
| Easy gym session, cool room | 0.5–0.8 L/hr |
| Team sport training | 1.0–1.5 L/hr |
| Match day or a long run in the heat | 1.5–2.5+ L/hr |
How to measure your own: weigh yourself before and after a session (minimal clothing, towel off first). Every 1kg you lose is roughly 1 litre of sweat. Add whatever you drank during the session.
Sweat sodium: how salty you are
This is the part most people never think about, and it's largely genetic. Training and heat acclimatisation shift it a bit, but if you're a salty sweater, you'll generally stay one.
Signs you might be on the higher end:
- White, crusty salt marks on your hat, shirt or skin after training
- Sweat that stings your eyes
- Sweat that tastes noticeably salty
- Feeling flat or washed out after long, hot sessions even when you've drunk plenty of water
Putting the numbers together
Here's what sodium loss looks like in practice, using the ~950mg/L average:
| Scenario | Sweat lost | Approx. sodium lost |
|---|---|---|
| 1 hr gym session | 0.7 L | ~650mg |
| 90 min footy training | 2.0 L | ~1,900mg |
| 2 hr long run, hot day | 3.5 L | ~3,300mg |
| 8 hr shift on site in summer | 6+ L | ~5,700mg+ |
And that's for an average sweater. A salty sweater could lose double these figures.
Why most sports drinks fall short
Traditional sports drinks typically contain somewhere around 400–500mg of sodium per litre. That level was designed largely around taste and carbohydrate delivery, not around matching what people actually sweat out.
So if you lose 1,900mg at footy training and replace it with a litre of a typical sports drink, you've put back about a quarter. Many electrolyte tablets aren't much better per serve.
The other problem is sugar. Many sports drinks pack 30g+ of sugar per bottle, which is fine mid-marathon, and less useful if you're sipping it through a gym session or a workday.
Do you actually need electrolytes?
Honestly, not always.
If you're doing a 30-minute session in an air-conditioned gym and eating a normal diet, food and water will cover you. Your meals already contain sodium.
Where sodium replacement starts to matter:
- Sessions over ~60–90 minutes
- Training or working in the heat
- Heavy sweaters and salty sweaters
- Multiple sessions a day, or back-to-back days (tournaments, pre-season)
- Long shifts in physical, hot jobs (construction, mining, trades)
If that's you, plain water alone replaces the fluid but not the sodium.
Where VYTL fits
We built VYTL because the numbers above didn't match what was on the shelf.
One serve of VYTL contains:
- 900mg sodium
- 300mg potassium
- 150mg magnesium
- No added sugar
Mixed into 500ml of water, that's a sodium concentration in the range of what an average person actually sweats, rather than a fraction of it.
Quick summary
- The average person loses ~900–1,000mg of sodium per litre of sweat, with a range of ~200mg to 2,000mg+
- Sweat rates run from 0.5 to 2.5+ litres per hour depending on intensity and heat
- A 90-minute training session can cost you ~2,000mg of sodium
- Typical sports drinks provide ~400–500mg per litre
- For short, cool sessions, food and water are enough. For long, hot or heavy-sweat sessions, sodium replacement makes sense.
This article is general information only and isn't medical advice. If you have a medical condition, including high blood pressure or kidney issues, or you're on a sodium-restricted diet, talk to your doctor before using electrolyte products.
References
- Baker LB (2017). Sweating rate and sweat sodium concentration in athletes: a review of methodology and intra/interindividual variability. Sports Medicine, 47(Suppl 1).
- Barnes KA et al. (2019). Normative data for sweating rate, sweat sodium concentration, and sweat sodium loss in athletes. European Journal of Applied Physiology, 119.
- Baker LB et al. (2016). Normative data for regional sweat sodium concentration and whole-body sweating rate in athletes. Journal of Sports Sciences, 34(4).