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 Acetyl L Carnitine HCL 500mg per serving 180 Capsules The Right Way to Take L Carnitine to Boost Your Training Get Rid of Fishy L Carnitine Smell: Essential Fixes Tonum 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 Linus Pauling Institute Oregon State University