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 How to Inject L Carnitine for Weight Loss Safely Trimethylaminuria: Understanding and Treating Fish Odor Syndrome 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. Does Carnitine Cause Body Odor? Lume Deodorant L Carnitine L Tartrate Powder True Protein