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 L Carnitine is not a magic fat burner , It wont melt fat, build muscle, or replace hard work., The only thing it burns is your money , Stick to the basics Nutrition, Training & Consistency. Acetyl L Carnitine Supplement: Uses, Benefits, Side Effects, Dosage, A Welltopia Pharmacy 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 Side Effects & Safety: A Complete Guide The Science of Good Health