Why Sodium Matters: Understanding Your Sweat Losses

Sodium is the main electrolyte you lose in sweat, and the amount varies more than tenfold between athletes, from around 200 mg to over 2,000 mg per litre. Knowing where you sit on that spectrum is one of the biggest upgrades you can make to your fueling.

What sodium actually does

Sodium helps your body hold fluid in the bloodstream, which supports blood volume, cooling and cardiovascular function. It's also essential for nerve signals and muscle contraction. When you sweat heavily for hours, those losses add up and can affect how well you perform and recover.

Why everyone's sweat is different

Sweat sodium concentration is largely determined by genetics and stays fairly stable across your life. Heat acclimation and diet can nudge it a little, but a "salty sweater" tends to stay salty. Combine that with sweat rate and you get a wide range of total losses:

That's why a one-size-fits-all sports drink rarely fits anyone perfectly.

Signs you might be a salty sweater

1. White, crusty salt marks on your kit or skin after training.
2. Sweat that stings your eyes or tastes very salty.
3. Craving salty food after long sessions.
4. Feeling flat or headachy after long, hot efforts despite drinking plenty.

None of these are definitive, but if several sound familiar, you may need more sodium than a typical sports drink provides. A professional sweat test gives the most accurate answer.

How to use this information

For sessions under an hour, most athletes don't need extra sodium. For longer or hotter efforts, match your intake to your losses. Lighter sweaters may do well with 300–500 mg per litre of fluid. Heavier, saltier sweaters often benefit from 1,000–1,500 mg per litre. Endura Fuel range offers different strengths so you can match your drink to your sweat.

The takeaway

Sodium needs are personal. Pay attention to the clues your body gives you, consider a sweat test, and choose an electrolyte strength that matches your losses rather than guessing.