Are L Carnitine and L Carnosine the Same? Anti Aging Systems l Carnitine Supplementation in Recovery after Exercise L Carnitine Is It Good or Bad for your Heart? Hammer Nutrition L carnitine is effective for both fat loss and athletic performance. However, oral L carnitine has lower bioavailability and can be harmful at high doses, so it should be avoided. , Even cardiologists L Carnitine: Benefits, Uses, Side Effects, and More