L Carnitine Benefits for Male Erectile Dysfunction 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 Amazon.com: Muscle Pharm L Carnitine 3000, The Ultimate Liquid L Carnitine Supplement for High Performance, Supports Metabolism, Hydration & Energy, Zero Sugar, Low Calories, Peach Nectarine Flavor, 32 Servings : Everything Else L Carnitine Benefits: A Complete Research Based Guide