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 Potential Adverse Effects of L Carnitine Marnys L Carnitine Side Effects & Safety: A Complete Guide The Science of Good Health L carnitine: Science Backed Benefits, Risks, and More Acetyl carnitine erectile dysfunction: What the evidence and real world use actually show L Carnitine Benefits for Male Erectile Dysfunction