L Carnitine Injectable vs Oral: Which Works Better for Canadians Beneficial effects of l carnitine supplementation for weight management in overweight and obese adults: An updated systematic review and dose response meta analysis of randomized controlled trials ScienceDirect When Injectable L Carnitine Is Chosen Over Supplements for Wellness Support 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