Trimethylaminuria: Definition, symptoms, and more Dietary supplementation of l carnitine ameliorates metabolic syndrome independent of trimethylamine N oxide produced by gut microbes in high fat diet induced obese mice Food & Function (RSC Publishing) 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 Pharmacokinetics of L Carnitine : Clinical Pharmacokinetics