L Carnitine Linus Pauling Institute Oregon State University Did You Know? Some people report a fishy smell after supplementing with L carnitine. This happens because certain gut bacteria convert carnitine to trimethylamine, a malodorous compound found in rotting fish. L Carnitine in the Treatment of Psychiatric and Neurological Manifestations: A Systematic Review Do you or someone you love smell like fish? It could be Fish Odor Syndrome! #fishodorsyndrome #fishy #fishysmell #fishodor 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 Did You Know? Some people report a fishy smell after supplementing with L carnitine. This happens because certain gut bacteria convert carnitine to trimethylamine, a malodorous compound found in rotting fish.