What is L Carnitine? L Carnitine is a naturally occurring amino acid derivative that the human body can synthesize itself. It is mainly found in red meat and dairy products. [1] Core Benefits of L Carnitine Benefits: A Complete Research Based Guide Association between fatigue, peripheral serotonin, and L carnitine in hypothyroidism and in chronic fatigue syndrome American ME and CFS Society ONLY NATURAL PET Thyroid Support Supplement for Cats Multivitamin with L Carnitine & Lemon Balm Vet L carnitine supplementation for the management of fatigue in patients with hypothyroidism on levothyroxine treatment: a randomized, double blind, placebo controlled trial. Semantic Scholar