L Carnitine is Underrated. New Meta Review Reminds Us Why. Arcicar (often containing Acetyl L Carnitine or L Carnitine) is a supplement primarily used to support cellular energy production and nervous system health. It is particularly valued for its high bioavailability, meaning the body absorbs 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 give IV Liquid L Carnitine 3000: Metabolism & Energy Support