Injectable L Carnitine for Slimming: Does It Really Work? National Medical Resources Inc L carnitine Fat Burning Timeline Effects in 412 Weeks Tonum Vitamin B6 Linus Pauling Institute Oregon State University 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 give IV L Carnitine 3000 Liquid Shots, Blue Razz, 16 fl oz (473 ml)