Why your sweat smells like cat urine during a workout
During intense physical activity, you may suddenly notice that your sweat has a sharp, unpleasant odor — often compared to the smell of cat urine. While alarming at first, this phenomenon has a clear biochemical basis and often points to a temporary imbalance in how your body processes energy. The scent is usually caused by ammonia, a by-product of protein metabolism, being excreted through the skin. While this isn’t typically dangerous, it’s a physiological response worth understanding, reported by G.Business.
What causes ammonia-smelling sweat
Under normal conditions, your body generates energy by breaking down carbohydrates — primarily glycogen stored in your liver and muscles. However, when carbohydrate intake is insufficient (due to fasting, low-carb diets, or depleted glycogen stores from prior workouts), your body turns to protein as an alternative fuel. When proteins are broken down, ammonia is produced as a waste product. The kidneys usually excrete ammonia through urine, but if the body is overwhelmed — such as during intense exercise — some of that ammonia is released through sweat.
This process is part of the body’s natural compensation mechanism. However, if it occurs regularly, it may indicate long-term imbalances in nutrition or metabolism. Ammonia in sweat may also be more pronounced when you're dehydrated or using certain supplements like BCAAs. The odor tends to be more noticeable in enclosed spaces, on synthetic workout clothing, or when combined with bacteria on the skin.
When are you most at risk of this odor
There are specific scenarios in which ammonia odor is more likely to appear. First, people training on an empty stomach often have depleted glycogen reserves, pushing the body to tap into protein for energy. Second, those following low-carbohydrate, high-protein diets are more prone to higher ammonia production during physical exertion. Third, excessive protein supplementation can overload the system, especially if not matched by hydration or balanced meals.
Additionally, individuals doing endurance training — such as long-distance running or high-intensity interval training — may experience this more frequently. Hot environments, sauna suits, and poor ventilation can exacerbate the smell. Even certain medications that affect kidney or liver function may play a role. Paying attention to when and how this odor occurs can help determine whether it's an isolated event or a symptom of something systemic.
Health implications and red flags
While ammonia-smelling sweat is often harmless and reversible, there are cases where it may signal a need for medical attention. If the odor persists regardless of diet or workout level, it might point to kidney strain, liver stress, or a metabolic disorder. Symptoms such as fatigue, confusion, dizziness, or unusually dark urine should not be ignored. Likewise, if the smell is present even without exercise, especially during rest or sleep, a medical check-up is warranted.
Blood tests can help identify elevated urea or creatinine levels, liver enzyme irregularities, or vitamin deficiencies (like B12, folate, or magnesium). In rare cases, genetic disorders such as urea cycle defects can also cause ammonia buildup. While uncommon, athletes and bodybuilders who push the body to extremes are more at risk. Prevention is often easier than treatment — and starts with listening to your body.
How to prevent or reduce the ammonia smell
There are several strategies to reduce or eliminate the ammonia-like odor in sweat. Begin by ensuring adequate carbohydrate intake before workouts — even a small portion like a banana or slice of wholegrain toast can prevent the body from breaking down protein. Secondly, stay hydrated throughout the day and especially during exercise: dehydration significantly increases ammonia concentration in sweat. A pre-workout hydration goal of 500 ml and 100–150 ml every 15–20 minutes during exercise is a good baseline.
Third, reduce or balance protein supplements. Many athletes overuse BCAA or creatine without understanding their metabolic impact. Whole foods with natural amino acid profiles are generally better. Fourth, wear breathable, moisture-wicking fabrics and wash workout clothes regularly. And lastly, consider consulting a sports nutritionist for a personalized plan — especially if you’re training for competitions or weight loss. These small changes can significantly improve your training experience and long-term health.
Sweat is your body’s messenger
Sweat is more than just a cooling mechanism — it’s a biological language your body uses to report internal conditions. A sudden, persistent smell of ammonia isn’t just inconvenient — it’s a sign your metabolism might be out of sync. In the same way that sweet-smelling sweat may signal diabetes or a sour smell could hint at bacterial imbalances, ammonia indicates your body is breaking down protein for fuel.
Understanding these signals allows you to adjust your lifestyle proactively. If this odor becomes a regular feature of your workouts, it’s worth rethinking your nutrition, hydration, and supplement strategies. And if any symptoms point to more serious underlying issues, medical advice is essential. Listen to your sweat — it says more than you think.
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