Get Rid of Fishy L Carnitine Smell: Essential Fixes Tonum Investigating the Association between Low Trimethylamine N Oxide Level TACG Dove Medical Press TMAO (Trimethylamine oxide) biocrates life science Unlocking the Health Benefits of L Carnitine and Potential Side Effects Your Health Magazine 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.