How much salt is in sweat?

Sodium and chloride are each typically in the range of 10-90 mmol/L, but the exact figure depends strongly on sweat rate and heat acclimatization. Faster sweating leaves less time to reabsorb salt, so sweat becomes saltier (Baker 2019).

Why does sweat taste salty?

Because its main dissolved solutes are sodium and chloride, the two ions that make up table salt. They account for most of the roughly 1% of sweat that is not water.

Does everyone's sweat have the same composition?

No. Sweat sodium and chloride can vary severalfold between people and even for the same person on different days, driven by sweat rate, heat acclimatization, diet and hydration. Potassium is more stable at about 2-8 mmol/L.

What else is in sweat besides water and salt?

Smaller amounts of potassium (2-8 mmol/L), lactate (5-40 mmol/L), urea (4-12 mmol/L), ammonia (1-8 mmol/L), and trace calcium, magnesium, bicarbonate and amino acids (Baker 2019).

Does sweating remove toxins from the body?

Only minimally. Sweat is overwhelmingly water and salt; waste products such as urea and ammonia are present but in small amounts. The kidneys and liver, not the sweat glands, do the body's main filtering.

Research

What Is Sweat Made Of? Composition and Electrolytes

Sweat is mostly water. Eccrine sweat, the watery fluid the body uses to cool itself, is about 99% water; the remaining ~1% is a mix of dissolved solutes. The two most abundant are sodium and chloride, the components of table salt, each typically in the range of 10-90 mmol/L. Sweat also contains potassium, lactate, urea, ammonia, calcium, magnesium and trace amino acids. This page sets out the verified concentration ranges for each component, with sources, and explains why the numbers vary so much from person to person and moment to moment.

By the Sweat Explained Editorial Team · Published 2026-07-13 · Last reviewed 2026-07-13 · Educational information, not medical advice.

Key statistics at a glance

~99%
of eccrine sweat is water
Cleveland Clinic (secondary)
10-90 mmol/L
typical sodium concentration in sweat
Baker 2019
10-90 mmol/L
typical chloride concentration in sweat
Baker 2019
2-8 mmol/L
typical potassium concentration, relatively stable
Baker 2019

Sweat is mostly water

By volume, eccrine sweat is overwhelmingly water, commonly given as about 99%. Sodium and chloride, the two ions that make up table salt, account for most of the small remaining fraction, which is why sweat tastes salty. Everything else, from potassium to trace amino acids, is present in much smaller amounts.

That is why heavy, prolonged sweating is primarily a loss of water and salt: the fluid leaving the skin is dilute, but over hours of heat or exercise the cumulative loss of water, sodium and chloride can be substantial. The dissolved solutes are what make sweat more than plain water, and what researchers measure when they study sweat composition.

What sweat contains: concentration ranges

The table lists typical concentration ranges for the main solutes in eccrine sweat, compiled in a comprehensive 2019 physiology review. Values are broad ranges, not fixed constants, because sweat composition shifts with sweat rate, region, heat acclimatization, diet and individual differences.

Typical composition of eccrine sweat (Baker 2019)
Component	Typical range in sweat	Role / notes
Water	~99% by volume	The bulk of sweat; the vehicle for cooling by evaporation
Sodium (Na+)	10-90 mmol/L	Main electrolyte; rises with higher sweat rate
Chloride (Cl-)	10-90 mmol/L	Tracks sodium; together they make sweat salty
Potassium (K+)	2-8 mmol/L	Relatively stable across conditions
Lactate	5-40 mmol/L	Byproduct of sweat gland metabolism
Urea	4-12 mmol/L	Nitrogen waste product
Ammonia	1-8 mmol/L	Nitrogen-containing solute
Calcium (Ca2+)	0.2-2.0 mmol/L	Trace mineral
Magnesium (Mg2+)	0.02-0.40 mmol/L	Trace mineral
Bicarbonate (HCO3-)	0.5-5.0 mmol/L	Contributes to sweat pH

Ranges are from a peer-reviewed physiology review and reflect wide biological variation, not a single fixed value.

Why sodium and chloride vary so much

Sodium and chloride are the standout electrolytes, and their concentration is the most variable part of sweat. Sweat begins in the gland's secretory coil as a fluid similar to the fluid around cells, then passes up a duct where much of the sodium and chloride is reabsorbed back into the body before the sweat reaches the skin. How much is reabsorbed depends heavily on how fast sweat is flowing.

At low sweat rates the duct has time to reclaim most of the salt, so sweat is more dilute; at high sweat rates, salt races through faster than it can be reabsorbed, so sweat sodium and chloride climb toward the top of the 10-90 mmol/L range. Heat acclimatization trains the glands to conserve salt, lowering sweat sodium, while factors such as diet and hydration also shift the numbers. This is why a single 'correct' sweat sodium value does not exist.

Potassium, lactate and the minor solutes

Unlike sodium and chloride, potassium stays fairly constant, usually 2-8 mmol/L, and changes little with sweat rate. Lactate and urea appear at higher concentrations than they do in blood because they are partly byproducts of the sweat gland's own metabolism and of waste excretion, not simply filtered from plasma. Ammonia, calcium, magnesium, bicarbonate and small amounts of amino acids round out the mixture.

These minor solutes are why sweat is being explored as a fluid for non-invasive biosensing. For everyday purposes, though, the practical picture is simple: sweat is water plus salt, with a scattering of other substances in small amounts.

What this means in practice

The plain-language takeaway: when you sweat heavily, you are mainly losing water and salt (sodium and chloride), which is why prolonged heat or exercise makes both fluid and electrolyte replacement relevant. The exact salt content of one person's sweat can differ severalfold from another's, and even from their own sweat on a cooler day, so published ranges describe a population, not a fixed personal number.

Sweat composition itself is normal physiology, not a medical condition. If sweating is unusually heavy, has changed noticeably, or comes with other symptoms, that is worth raising with a clinician. Nothing here is a diagnosis or medical advice.

Methodology and limitations

The concentration ranges on this page are taken from a comprehensive peer-reviewed physiology review (Baker, Temperature, 2019) and a companion review on the mechanisms determining sweat composition (Baker & Wolfe, European Journal of Applied Physiology, 2020). The '~99% water' figure is a widely cited approximation, sourced here to a major medical center's patient reference and labeled secondary. Each figure was traced to its source and confirmed.

Limitations: sweat composition varies widely with sweat rate, body region, heat acclimatization, hydration, diet and individual differences, so the values are ranges rather than fixed constants, and a personal sweat profile can fall outside a population range. Most published figures describe eccrine sweat collected under specific conditions; sampling method itself affects measured values. This page is general education, not a diagnosis or medical advice.

Frequently asked questions

What is sweat made of?: Sweat is about 99% water. The remaining ~1% is mostly sodium and chloride (the components of table salt), plus smaller amounts of potassium, lactate, urea, ammonia, calcium, magnesium and trace amino acids.
How much salt is in sweat?: Sodium and chloride are each typically in the range of 10-90 mmol/L, but the exact figure depends strongly on sweat rate and heat acclimatization. Faster sweating leaves less time to reabsorb salt, so sweat becomes saltier (Baker 2019).
Why does sweat taste salty?: Because its main dissolved solutes are sodium and chloride, the two ions that make up table salt. They account for most of the roughly 1% of sweat that is not water.
Does everyone's sweat have the same composition?: No. Sweat sodium and chloride can vary severalfold between people and even for the same person on different days, driven by sweat rate, heat acclimatization, diet and hydration. Potassium is more stable at about 2-8 mmol/L.
What else is in sweat besides water and salt?: Smaller amounts of potassium (2-8 mmol/L), lactate (5-40 mmol/L), urea (4-12 mmol/L), ammonia (1-8 mmol/L), and trace calcium, magnesium, bicarbonate and amino acids (Baker 2019).
Does sweating remove toxins from the body?: Only minimally. Sweat is overwhelmingly water and salt; waste products such as urea and ammonia are present but in small amounts. The kidneys and liver, not the sweat glands, do the body's main filtering.

Sources

Primary peer-reviewed studies and official sources first, then reviews and institutional framing (secondary).

Baker LB. Physiology of sweat gland function: the roles of sweating and sweat composition in human health. Temperature (Austin). 2019;6(3):211-259. Full text
Baker LB, Wolfe AS. Physiological mechanisms determining eccrine sweat composition. Eur J Appl Physiol. 2020;120(4):719-752. Full text
Cleveland Clinic. Sweat: what it is and why you sweat. Cleveland Clinic health library (patient reference) - '~99% water'. (secondary) Cleveland Clinic

How to cite this page

Sweat Explained. What Is Sweat Made Of? Composition and Electrolytes. Published 2026-07-13; last reviewed 2026-07-13. Available at: https://sweatexplained.com/research/what-is-sweat-made-of

Please cite the original studies for the underlying figures. Journalists are welcome to link to this page; the charts are original renderings of the cited data.