Does Carnitine Cause Body Odor? Lume Deodorant Does L carnitine cause fishy body odor? Surprising Truth and Solutions Tonum 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 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.