Didn't another study show carnitine was good for the heart? Safety and efficacy of L carnitine supplementation in improving cardiac function of hemodialysis patients: a systematic review and meta analysis International Urology and Nephrology Springer Nature Link Carnitine Deficiency: What Is It, Causes, Symptoms, and More Osmosis L carnitine is primarily synthesized in the liver from the amino acids lysine and methionine through a series of four enzymatic reactions, with the liver and kidneys converting the precursor butyrobetaine into active