Does L carnitine cause fishy body odor? Surprising Truth and Solutions Tonum L Carnitine (Orange) Outlastlabz Most people talk about carnitine like it is one supplement. It is not. Acetyl L carnitine and L carnitine L tartrate do different jobs, and picking the wrong one for the wrong goal is where people 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 Scientists make breakthrough in studying the enzyme involved in fish odor syndrome