Pharmacokinetics of L Carnitine Clinical Pharmacokinetics Springer Nature Link 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 Carnitine Molecule of the Month September 2003 L Carnitine in the Treatment of Psychiatric and Neurological Manifestations: A Systematic Review PDF) [L carnitine treatment and fish odor syndrome: an unwaited adverse effect].