L Carnitine Oral Bioavailability NOW l Carnitine Supplement Unlock Peak Performance & Fertility with L Carnitine! Did you know that injectable L Carnitine is a game changer compared to oral supplements? While oral L Carnitine has low bioavailability (only ~14 18% 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