5 Health Benefits of L Carnitine Carnitine: the claims and why it may not work L Carnitine injection is recommended at 1 ampule every 2 3 days for best results. The L Carnitine is taken intravenously either by normal injection or using a butterfly needle. After taking this L Carnitine, you Acute L Carnitine Supplementation Does Not Improve CrossFit Performance: A Randomized, Double Blind, Placebo Controlled Crossover Study Frontiers L carnitine prevents lenvatinib induced muscle toxicity without impairment of the anti angiogenic efficacy