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 Injection vs. Oral Supplements: Which is More Effective? Katalyst Wellness Amazon.com: NuEthix Formulations Lipsomal L Carnitine Supplement 600mg with L Citrulline 1000mg for Healthy Weight Management, Fat Metabolism, Energy Production and Increased Blood Flow, for Men & Women : Health & Household Intestinal microbiota metabolism of l carnitine, a nutrient in red meat, promotes atherosclerosis Nature Medicine