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 Trimethylamine N Oxide From Gut Microbiota in Chronic Kidney Disease Patients: Focus on Diet Journal of Renal Nutrition What are the benefits and side effects of L carnitine (Levocarnitine)? bodyathlon Fishy Odor Syndrome (Trimethylaminuria): Causes, Symptoms, Diagnosis, and Treatment Mister Blister