The essential
October 9, 2026
Sodium for athletes: how much do you lose in sweat?
Quick answer
Sweating costs you sodium. Total loss depends on both sweat volume and sodium concentration, which vary separately.
Try this in training
White marks on a shirt are a clue, but they don’t measure your losses. On two comparable sessions, log heat, duration, what you drank and stomach comfort. Fine-tune the plan for heavy-sweat days without forcing extra fluid.
Keep reading
- What are electrolytes and what do they do?
- Water or electrolytes: what should you drink for training?
- Electrolytes for runners: plan your hydration
- BreathersBliss electrolytes
Sources
BREATHERSBLISS LAB
Sweat sodium loss has two parts: how much you sweat and how much sodium that sweat contains. A salty shirt alone cannot tell you either number precisely. Start with your training conditions before choosing an electrolyte powder.
Why sodium matters during exercise
Sodium helps regulate fluid distribution and supports nerve and muscle activity. Sweat contains water and electrolytes, including sodium and chloride. Losing some during a workout does not automatically mean you need a supplement: everyday food also supplies sodium.
Work out losses without guessing a target
The calculation is sweat volume in litres × sweat sodium concentration in mg/L. For an illustration, 0.8 L of sweat containing 700 mg/L gives a loss of 560 mg. These are example numbers, not your sweat profile or a recommended hourly intake.
Pre- and post-session body mass, adjusted for drinks and urine, can help estimate fluid loss. It cannot reveal sodium concentration. White marks on clothing are a clue rather than a measurement. A qualified sports nutrition professional can explain whether sweat testing is useful and how sampling affects the result.
Read the serving before the concentration
On European labels, salt equivalent is sodium multiplied by 2.5. That makes 600 mg sodium equivalent to 1.5 g salt; it is not an instruction to add table salt. Also distinguish a serving from a litre: one BreathersBliss stick contains 600 mg sodium whether you mix it in 300 or 500 ml.
The resulting concentrations are 2,000 mg/L and 1,200 mg/L respectively. A higher concentration does not mean a larger amount in the stick, better hydration or a personal hourly target. Keep the stated mixing directions.
Put sodium into the whole race plan
Record the weather, duration, drinks, food and stomach comfort across comparable sessions. Include sodium already present in gels, snacks and drinks before adding another source. Sodium cannot make overdrinking safe. If you have a prescribed salt restriction or kidney condition, discuss supplements with your clinician.
| Situation | Practical approach |
|---|---|
| Short session with little sweating | Water and usual meals may be sufficient. |
| Long, sweaty endurance session | Assess total food and drink intake, then personalise. |
| A label showing 600 mg | Check whether it means per serving or per litre. |
Common questions
Does salty sweat mean I should take extra sticks?
No. Clothing marks cannot determine a dose. BreathersBliss directions remain one stick per day; a wider endurance plan needs separate consideration.
Can potassium replace sodium?
No. They are different electrolytes. A high potassium figure does not tell you how much sodium a drink supplies.
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