What does the smell of your urine tell you?? TMAU: Diet to reduce a fishy odour Dietitian's Life Carnitine Deficiency MD Searchlight 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 Carnitine Cause Body Odor? Lume Deodorant