Current state of the treatment landscape of phenylketonuria Orphanet Journal of Rare Diseases 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 Urine smells like fish: Causes and treatment Why Does Asparagus Make Your Pee Smell? Find Out Here!