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 The bright and the dark sides of L carnitine supplementation: a systematic review Journal of the International Society of Sports Nutrition Springer Nature Link L Carnitine Oral Bioavailability NOW l Carnitine Supplement When to Take L Carnitine for Optimal Training Benefits Transparent Labs