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 Intestinal microbiota metabolism of l carnitine, a nutrient in red meat, promotes atherosclerosis Nature Medicine Pharmacokinetics of L Carnitine Clinical Pharmacokinetics Springer Nature Link L carnitine modified nanoparticles target the OCTN2 transporter to improve the oral absorption of jujuboside B ScienceDirect