Trimethylaminuria: Definition, symptoms, and more Probiotics for Body Odor: The Science Behind the Gut Skin Connection BioPhysics Essentials 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. 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 Does L carnitine cause fishy body odor? Surprising Truth and Solutions Tonum L Carnitine: Everything You Need to Know