PDF) [L carnitine treatment and fish odor syndrome: an unwaited adverse effect]. Potential Adverse Effects of L Carnitine Marnys Optimizing endurance performance in elite swimmers: effects of L carnitine supplementation and hydration strategies Applied Water Science 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