An ammonia-like body odor usually means your body is breaking down protein for energy and releasing the nitrogen byproducts through your sweat, breath, or urine. This is the most common explanation, and it’s often tied to diet, exercise, or dehydration. Less commonly, it can signal a problem with your kidneys or liver, which are the organs responsible for processing and removing ammonia from your blood.
How Your Body Normally Handles Ammonia
Your body produces ammonia constantly as a natural byproduct of protein digestion. When you eat protein, it breaks down into amino acids. Your liver converts the nitrogen from those amino acids into urea, a much less toxic compound, which your kidneys then filter out through urine. This system works quietly in the background, and you never notice it.
The smell becomes noticeable when something disrupts that cycle. Either your body is producing more ammonia than usual, your kidneys or liver aren’t clearing it efficiently, or the ammonia is being concentrated in your sweat to the point where you can smell it.
High-Protein Diets and Low-Carb Eating
This is the single most common reason healthy people suddenly notice an ammonia smell. Your body prefers carbohydrates as its fastest fuel source, converting them to glucose for energy. When carbs are scarce, your body turns to protein instead. That protein breaks down into amino acids, which your body converts into ammonia and then releases through urine and sweat.
If you’ve recently started a ketogenic diet, cut carbs significantly, or dramatically increased your protein intake, this is likely your answer. The fix is straightforward: add more carbohydrates back into your diet, or reduce protein intake to a level your body can process without the excess spilling over into sweat. Even a modest increase in carbs before workouts can make a noticeable difference.
Exercise and Ammonia in Sweat
Intense exercise accelerates the same process. When you push hard enough to deplete your glycogen (stored carbohydrate) reserves, your muscles start burning amino acids for fuel, producing ammonia as waste. This is why the smell tends to be strongest after long or particularly grueling workouts, especially if you exercised in a fasted state or without eating enough carbs beforehand.
Sweat itself contains ammonia at concentrations of 1 to 8 mmol/L, which is 20 to 50 times higher than what’s found in your blood. That’s because ammonia passively diffuses from your blood into the acidic fluid in your sweat glands, where it gets trapped. The less you sweat (due to dehydration or a slower sweat rate), the more concentrated those compounds become, making the smell sharper and more noticeable.
Dehydration Makes It Worse
When you’re not drinking enough water, two things happen. First, your urine becomes more concentrated, which means the ammonia and urea in it become more pungent. Second, dehydration delays your body’s sweating response by raising the temperature threshold at which you start to sweat. When sweat finally does come, it’s released in lower volume, concentrating the ammonia further. If you’ve noticed the smell mostly on hot days or after exercise, increasing your water intake is the simplest first step.
Kidney Problems and Ammonia Buildup
Your kidneys are the primary exit route for nitrogenous waste. When they aren’t functioning properly, urea builds up in the blood, and your body starts releasing ammonia through other channels: your breath, your skin, and your sweat.
Research published in Biomedicines measured breath ammonia at each stage of chronic kidney disease and found a dramatic, progressive increase. People in the earliest stage had breath ammonia levels around 636 parts per billion. By the most advanced stage, that number climbed to nearly 12,800 ppb, roughly 20 times higher. Skin emissions of ammonia were also significantly elevated in people with kidney disease compared to healthy individuals. Much of the ammonia on the breath actually comes from bacteria in the mouth breaking down the excess urea in saliva, rather than directly from the blood.
An ammonia or bleach-like smell on the breath is a recognized symptom of kidney failure, sometimes called uremic fetor. If you’re noticing a persistent ammonia odor that doesn’t change with diet or hydration, particularly if it’s on your breath, kidney function is worth investigating.
Liver Disease
Your liver is the organ that converts ammonia into urea in the first place. When it’s damaged or failing, ammonia can accumulate in the blood because that conversion process isn’t working properly. Liver disease produces a distinctive breath odor called fetor hepaticus, though ammonia is only a minor contributor to that smell. The dominant odors come from sulfur-containing compounds. Still, ammonia plays a supporting role, and people with severe liver disease often have elevated blood ammonia levels that can contribute to body odor changes.
Infections That Cause Ammonia Smells
Bacterial vaginosis can produce an ammonia-like odor, though it’s more commonly described as fishy. Some women notice a more chemical scent. Other symptoms that point toward BV include thin, watery discharge that’s white or gray, burning during urination, and itching around the vagina. Urinary tract infections can also make urine smell strongly of ammonia, though the mechanism is different: bacteria in the urinary tract break down urea, releasing ammonia directly.
Phantom Smells Without an External Source
Sometimes the ammonia smell isn’t actually coming from your body. Phantosmia is a condition where you perceive smells that aren’t there, and parosmia causes real smells to register as something else entirely. Both can be triggered by sinus infections, nasal polyps, allergies, viral infections (including COVID-19), and neurological conditions. If nobody else can detect the smell, or if it seems to come from inside your nose rather than your skin or breath, the issue may be with your sense of smell itself rather than your body chemistry.
Rare Genetic Conditions
Urea cycle disorders are rare inherited conditions where the body can’t efficiently convert ammonia to urea. While these are typically diagnosed in infancy, milder forms can remain hidden until adulthood, sometimes surfacing during periods of high protein intake, illness, or stress. Late-onset cases are uncommon and frequently go undiagnosed for years because the symptoms, which can include confusion, behavioral changes, and body odor, mimic other conditions.
A separate condition called trimethylaminuria causes a strong, often fishy or chemical body odor when the body can’t break down a specific compound from foods like eggs, fish, and certain legumes. Diagnosis requires a specialized urine test collected after eating a high-substrate meal (typically 300 grams of marine fish), with urine collected 2 to 12 hours afterward. Because the condition can be intermittent, testing sometimes needs to be repeated during periods when the odor is most noticeable.
Figuring Out What’s Causing Your Smell
Start with the most common explanations. If you’re eating a high-protein or low-carb diet, exercising intensely, or not drinking enough water, adjusting those habits for a week or two will tell you a lot. Add carbohydrates back before workouts, increase your water intake, and see if the smell fades.
If the smell persists regardless of diet and hydration changes, or if it’s concentrated on your breath rather than your skin, a basic blood panel can check kidney and liver function. A blood ammonia test has a normal reference range of 15 to 45 µg/dL, though exact ranges vary by lab. Blood urea nitrogen and creatinine levels give a picture of how well your kidneys are filtering waste. These are routine, inexpensive tests that can rule out or confirm organ-related causes quickly.