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. 12 Urine Smells What Do They Really Mean? Your urine can tell you a lot about what's happening inside your body. Changes in smell are often harmless, but sometimes What does the smell of your urine tell you?? Get Rid of Fishy L Carnitine Smell: Essential Fixes Tonum Trimethylaminuria (Fish Odor Syndrome or TMAU)