L Carnitine: Benefits, Side Effects, And Dosage, Per Dietitians SFI Health Acetyl L Carnitine 90c 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. Acetyl L Carnitine Weight Loss Support EHPLabs Holy Supps.co.uk 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 Tablets MSC Nutrition