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 Pharmacokinetics of L Carnitine Clinical Pharmacokinetics Springer Nature Link Systemic regulation of L carnitine in nutritional metabolism in zebrafish, Danio rerio Scientific Reports Revisiting the Role of Carnitine in Heart Disease Through the Lens of the Gut Microbiota