The Synergistic Effects of the Combination of L Carnitine and Lycopene on the Lycopene Bioavailability and Duodenal Health of Roosters Carnitine: the claims and why it may not work 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 Nanoparticle mediated L carnitine delivery for improved male fertility ScienceDirect