L Carnitine: Benefits, Uses, and Side Effects Lifespan Research Institute Trimethylamine N oxide (TMAO): Pathway, Cardiovascular Risk, Diet & LCMS MS Testing TMAO: how gut microbiota contributes to heart failure Translational Research 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 Gut microbiota metabolism of l carnitine and cardiovascular risk ScienceDirect When to take L carnitine: Dosage, forms, and side effects