Carnitine is made in the liver and kidneys, then stored in the skeletal muscles, heart, brain and sperm. Red meat and dairy produce are the primary dietary sources. Holland & Barrett provides carntine in its natural 'L' form; we do not use synthetic D-Carnitine. Carnitine is made in the liver and kidneys, then stored in the skeletal muscles, heart, brain and sperm. Red meat and dairy produce are the primary dietary sources. Holland & Barrett provides carntine in its natural 'L' form; we do not use synthetic D-Carnitine.