A recurring fishy odor could indicate a larger medical problem. 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 is not a magic fat burner It won't melt fat, build muscle, or replace hard work. The only thing it burns is your money Stick to the basics Acetyl L Carnitine Supplement: Uses, Benefits, Side Effects, Dosage, A Welltopia Pharmacy