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 L Carnitine Side Effects & Risks Keep your dog's heart strong and healthy! As dogs age, heart disease can become a common challengebut with the right support, you can help improve their quality of life. L Carnitine Supplementation in the Diabetic Heart ABC Cardiol