L carnitine is a naturally occurring amino acid structure that is made in the human brain, liver, and kidneys. L carnitine plays a critical role in energy production, as it converts fat into energy. L Carnitine Benefits, Uses, Dosage, Foods, Side Effects Dr. Axe Early research into L carnitine was often cited as underwhelming, showing negligible changes in muscle carnitine content and fat loss outcomes. However, these findings may have been limited by a short study window The effects of L carnitine in children with kidney failure undergoing dialysis: a systematic review Pediatric Nephrology Springer Nature Link