Potential Adverse Effects of L Carnitine Marnys Ultra L carnitine making me reek of rotting fish for 48 hours #lcarnitine #fishy #smell #trauma #fyp 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 Liquid 3000 Metabolic Support OstroVit L carnitine 210 g 11,29 EUR Official store OstroVit 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.