What Is L Carnitine? How Could It Help With Weight Management? Wellness Hub Carnitine: the claims and why it may not work Lets talk about L Carnitine, If youre in the gym community, youve probably heard of L Carnitine but what actually is it?, L Carnitine is a naturally occurring compound that plays a role in helping L Carnitine: Benefits, Side Effects, And Dosage, Per Dietitians Did You Know? Some people report a fishy smell after supplementing with L carnitine. This happens because certain gut bacteria convert carnitine to trimethylamine, a malodorous compound found in rotting fish.