L carnitine: what is it, health benefits and side effects Gut Derived Metabolite, Trimethylamine N oxide (TMAO) in Cardio Metabolic Diseases: Detection, Mechanism, and Potential Therapeutics Did You Know? Some people report a fishy smell after supplementing with L carnitine. This happens because certain gut bacteria convert carnitine to trimethylamine, a malodorous compound found in rotting fish. Trimethylaminuria: Definition, symptoms, and more Compounded Carnitine (L) Injection Empower Pharmacy L carnitine supplements can cause a fishy odor in the breath, sweat, and urine. This is likely due to the formation of trimethylamine (TMA). TMA is also responsible for the pungent smell of