L Carnitine Linus Pauling Institute Oregon State University Is L Carnitine Safe? Watch FIRST BEFORE Taking L Carnitine Supplements Trimethylaminuria (Fish Odor Syndrome or TMAU) Does L carnitine cause fishy body odor? Surprising Truth and Solutions Tonum 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. 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.