When to take L carnitine: Dosage, forms, and side effects Does Carnitine Cause Body Odor? Lume Deodorant Does L carnitine cause fishy body odor? Surprising Truth and Solutions Tonum 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 PDF) [L carnitine treatment and fish odor syndrome: an unwaited adverse effect].