L Carnitine: Benefits, Uses, Side Effects, and More 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 Trimethylaminuria: Understanding and Treating Fish Odor Syndrome L carnitine supplements can cause a fishy odor in the breath, sweat, and urine. This is likely due to the formation of trimethylamine (TMA). TMA is also responsible for the pungent smell of Treatments of trimethylaminuria: where we are and where we might be heading ScienceDirect