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: Benefits, Forms, Dosing, and Side Effects Dr Brad Stanfield Breakthrough in studying the enzyme that ultimately produces fish odor syndrome EurekAlert! L carnitine: properties and health benefits Marnys Carnitine Deficiency: What Is It, Causes, Symptoms, and More Osmosis Trimethylamine Oxide an overview ScienceDirect Topics