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. Get Rid of Fishy L Carnitine Smell: Essential Fixes Tonum Stabilizing the enzyme in fish odor syndrome Trimethylaminuria: FMO3 mutations that cause malodorous body odor Trimethylaminuria, or fish odour syndrome is an uncommon condition that causes an unpleasant, fishy smell. The body is unable to turn a strong smelling chemical called trimethylamine produced in the gut when Treatments of trimethylaminuria: where we are and where we might be heading ScienceDirect