The bright and the dark sides of L carnitine supplementation: a systematic review Journal of the International Society of Sports Nutrition Springer Nature Link Injectable vs Oral L Carnitine: Which Works Better? AWP L carnitine supplements bioavailability is very less and according to some studies it takes 8 to 12 weeks for for loss results, so if you decide to supplement with oral L carnitine do take it in 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