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 Allergy: Symptoms and Treatment Options (2026) Wyndly Trimethylaminuria: Understanding and Treating Fish Odor Syndrome Supplements & Body Odor ConsumerLab.com Treatments of trimethylaminuria: where we are and where we might be heading ScienceDirect Trimethylaminuria (Fish Odor Syndrome or TMAU)