By Lachlan Maskell, Co-founder, Fluence | 05/07/2026
Every electrolyte brand in Australia has picked a number. Some sell you 1000mg of sodium per serve, some 500mg, ours delivers 250mg. Each brand can tell you a story about why its number is right. The more useful question is: how much sodium do you actually lose when you sweat? Because that number, not any brand's marketing, is what should drive your choice.
The genuinely inconvenient answer, and the reason this article needs 1200 words rather than one sentence, is that the research shows enormous individual variation. Let's walk through it.
The two numbers that matter
Your sodium loss in any session is simple multiplication:
Sweat rate (litres per hour) x sweat sodium concentration (mg per litre) = sodium lost per hour
Both inputs vary wildly between people, and both vary within the same person depending on heat, humidity, intensity, fitness and heat acclimatisation. That variation is the whole story.
Input 1: sweat rate
The most comprehensive review of this data, by Lindsay Baker in Sports Medicine (2017), puts typical exercise sweat rates at roughly 0.5 to 2.0 litres per hour, with some large athletes in hot conditions exceeding that. The American College of Sports Medicine's position stand on fluid replacement cites a similar spread and notes that losses climb with intensity, heat and humidity, which matters rather a lot in an Australian summer.
Practical anchors:
- Easy gym session, air conditioning: often around 0.5 L/hour or less
- Steady run in mild weather: commonly 1 to 1.5 L/hour
- Hard running or cycling in heat and humidity: 1.5 to 2.5 L/hour for some people
Input 2: sweat sodium concentration
This is where the individual lottery really shows. Baker's review reports sweat sodium concentrations ranging from roughly 10 to 90 mmol/L, which converts to about 230mg to 2,070mg of sodium per litre of sweat, with typical values around 35 mmol/L, or roughly 800mg per litre. Precision Hydration, which has run sweat tests on thousands of athletes, reports a similar spread in its published advice and built its entire multi-strength product range around it.
In plain terms: two runners doing the same session can lose sodium at rates that differ by a factor of five or more. Neither is broken. Sweat sodium concentration is substantially genetic, though it also drops as you become heat-acclimatised.
Doing the maths on real sessions
Combine the ranges and you get realistic scenarios:
| Scenario | Sweat rate | Sweat sodium | Sodium lost |
|---|---|---|---|
| 45 min gym, air con, average sweater | ~0.4 L total | ~800 mg/L | ~320mg |
| 1 hour run, warm evening, average sweater | ~1.2 L | ~800 mg/L | ~960mg |
| 1 hour run, hot day, salty sweater | ~1.5 L | ~1,500 mg/L | ~2,250mg |
| 3 hour ride, humid morning, salty sweater | ~4.5 L | ~1,500 mg/L | ~6,750mg |
These are illustrations built from the published ranges above, not measurements of you. But they make the key point: sodium losses in normal life run from a few hundred milligrams to several thousand, depending on who you are and what you did.
Before you panic: your diet is already in the game
Here is the nuance that most electrolyte marketing skips. According to the Australian Nutrient Reference Values, most Australians already consume well above the suggested dietary sodium target through ordinary food. Your body also actively defends its sodium balance; hormones adjust how much you retain and excrete.
So for a sedentary day, or a short session with a normal meal on either side, you generally do not need supplemental sodium at all. Water plus food covers it. Health bodies who push back on daily electrolyte marketing are right about that, and we would rather agree with them than pretend otherwise.
Supplementation earns its place when losses are concentrated and food is not immediately in the picture: during and after sweaty sessions, in sustained heat, on long outdoor working days, during fasting windows, or when travel disrupts normal eating and drinking.
What this means for choosing a serve size
Now the numbers turn into a buying decision.
When 250mg per serve is enough. If your typical session is under an hour at moderate intensity, or your day involves heat and steady sweating rather than drenching efforts, your per-session losses likely sit in the hundreds of milligrams, and some of that is replaced at your next meal. A moderate serve such as Base 250, with 250mg sodium, 250mg potassium, 60mg magnesium and 40mg vitamin C, replaces electrolytes lost through sweat at a scale that matches that day, without stacking a large salt load on top of a diet that probably already exceeds targets. Zero sugar, zero calories, built for daily use. You can also simply take a second sachet on a bigger day; two serves is 500mg of sodium, and the serve size becomes a dial rather than a ceiling.
When you genuinely need more. If you are running long in Queensland humidity, finishing sessions crusted in white salt marks, cramping late in long events, or sweating heavily for multiple hours, your losses can reach several thousand milligrams. At that point, higher-sodium products in the 500 to 1000mg tier, or multiple serves of a moderate product taken across the session, are the honest recommendation. This is exactly the athlete Precision Hydration, LMNT and Sodii built for, and we will happily say so.
Signals worth noticing. White salt stains on dark clothing and stinging eyes suggest saltier sweat. A simple field estimate of sweat rate: weigh yourself before and after a session (dry, minimal clothing), add back what you drank; each kilogram lost is roughly a litre of sweat. It is not a lab test, but it turns guesswork into a rough personal number, and sports dietitians use exactly this method.
Where hydrogen fits into our formula
A quick note on why Base 250's magnesium is listed as elemental: it reacts with water in your glass to release dissolved molecular hydrogen, one of the most studied molecules in wellness science, and small enough to cross the blood-brain barrier. Research suggests molecular hydrogen may support antioxidant capacity, lower perceived exertion and aid recovery - the science is promising but still developing. That is a separate question from your sodium maths, and we keep the two arguments apart deliberately; the state of the hydrogen evidence is laid out on our science page.
The short version
- Sweat rate: roughly 0.5 to 2 L/hour for most exercisers.
- Sweat sodium: roughly 230 to 2,070mg per litre; around 800mg/L is typical.
- Your loss per session: anywhere from a few hundred mg to several thousand.
- Sedentary days: water and food are enough. Sweaty days: replace what you lost, scaled to the day.
- Moderate days are most days, which is why our default serve is 250mg, with the option to double up, and why we will point genuine heavy sweaters at higher-sodium options without flinching.
If you want to see how the moderate tier is put together, start at the electrolyte hub, or try all three flavours in the Trio 15-Pack and run your own experiment across a fortnight of real sessions.
Sources
- Baker LB. Sweating rate and sweat sodium concentration in athletes: a review of methodology and intra/interindividual variability. Sports Medicine, 2017. https://pubmed.ncbi.nlm.nih.gov/28332116/
- Sawka MN et al. American College of Sports Medicine position stand: exercise and fluid replacement. 2007. https://pubmed.ncbi.nlm.nih.gov/17277604/
- McDermott BP et al. National Athletic Trainers' Association position statement: fluid replacement for the physically active. Journal of Athletic Training, 2017. https://pubmed.ncbi.nlm.nih.gov/28985128/
- National Health and Medical Research Council, Nutrient Reference Values: Sodium. https://www.eatforhealth.gov.au/nutrient-reference-values/nutrients/sodium
- Precision Hydration, sweat sodium advice. https://www.precisionhydration.com/performance-advice/hydration/why-you-need-to-know-how-salty-your-sweat-is/
- Ohsawa I et al. Hydrogen acts as a therapeutic antioxidant by selectively reducing cytotoxic oxygen radicals. Nature Medicine, 2007. https://pubmed.ncbi.nlm.nih.gov/17486089/
This article is general information only and is not medical advice. If you have a medical condition, are pregnant or breastfeeding, or take prescribed medication, talk to your doctor or pharmacist before changing your hydration or supplement routine.
