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 100% Pure L Carnitine by Genetix Nutrition Essentials Nutrition Warehouse L CARNITINE Genetix Nutrition 3 Effective Hacks to Eliminate Fishy Dog Odor 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. Is L Carnitine Safe? Watch FIRST BEFORE Taking L Carnitine Supplements