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. Trimethylamine and Trimethylamine N Oxide, a Flavin Containing Monooxygenase 3 (FMO3) Mediated Host Microbiome Metabolic Axis Implicated in Health and Disease Drug Metabolism and Disposition Full article: Trimethylamine N oxide formation, the bacterial taxa involved and intervention strategies to reduce its concentration in the human body Trimethylamine Noxide: breathe new life Subramaniam 2018 British Journal of Pharmacology Wiley Online Library Trimethylaminuria: FMO3 mutations that cause malodorous body odor Carnitine Deficiency: What Is It, Causes, Symptoms, and More Osmosis