Most Likely Causes (Ranked)
When carbohydrate intake is low, the body breaks down protein for energy, producing ammonia as a byproduct. Keto, Atkins, and other low-carb diets commonly cause ammonia-smelling sweat.
During long or intense workouts, glycogen stores deplete and the body switches to burning amino acids. The ammonia byproduct is excreted through sweat.
Concentrated sweat contains more urea relative to water, making the ammonia smell more noticeable.
Kidneys normally filter urea from blood. If kidney function is impaired, urea builds up and can be excreted through sweat, producing a persistent ammonia smell.
How to Fix It
Adjust Pre-Workout Nutrition
$0Most effective fix.
- 1Eat carbs 1-2 hours before exercise — a banana, toast, or oatmeal provides glycogen.
- 2For workouts over 60 minutes, consume carbs during exercise (sports drink, gel).
- 3If on a low-carb diet, consider "carb cycling" — adding carbs on heavy workout days.
Stay Hydrated
$0Dilutes ammonia in sweat.
- 1Drink 16-20 oz water 2 hours before exercise.
- 2Drink 7-10 oz every 10-20 minutes during exercise.
- 3Monitor urine color — pale yellow means well-hydrated.
See a Doctor
$50-200If smell persists at rest despite diet/hydration changes.
- 1Blood work to check kidney function (BUN, creatinine).
- 2Urinalysis to check for protein or other abnormalities.
- 3Most cases are dietary, not medical.
When to Call a Professional
Ammonia smell at rest, not just during exercise — possible kidney issue.
Swelling in legs or face with ammonia smell — kidney function test warranted.
Persistent despite adequate carbs and hydration — see a doctor.
How to Prevent It
Eat adequate carbs, especially before exercise.
Stay well-hydrated.
Don't exercise fasted if ammonia smell is a problem.
Balance protein intake — more isn't always better.
Why Low-Carb Diets Cause Ammonia Sweat
When carbs are scarce, the body turns to amino acids for energy through a process called gluconeogenesis. The nitrogen in amino acids must be removed, and it's converted to urea. When urea levels rise faster than the kidneys can clear them, the excess is excreted through sweat as ammonia.
This is harmless but unpleasant. Simply eating 30-50g of carbs before a workout provides enough glycogen to prevent the body from relying on protein for fuel.
Frequently Asked Questions
No. It's a sign your body is using protein for fuel instead of carbs. It's harmless but indicates you should eat more carbs around exercise.
Rarely. If ammonia smell persists at rest (not just during exercise) and doesn't respond to diet changes, see a doctor for kidney function testing.
Ammonia from sweat saturates fabric and doesn't wash out easily. Soak ammonia-smelling gym clothes in vinegar water (1 cup per gallon) before washing.
Yes. Less water in sweat means higher concentration of urea/ammonia. Hydrating properly dilutes these compounds.