Targeting Skeletal Muscle Dysfunction With L Carnitine for the Treatment of Patients With Chronic Obstructive Pulmonary Disease In Vivo Build Muscle with L Carnitine 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 Why Take Carnitine? NOW Foods Amazon.com: Lean Sauce Liquid L Carnitine 3500 Pre Workout Formula, Stimulant Free for Optimal Absorption, Energy & Muscle Support 15% More (3500 vs 3000) : Everything Else Early research into L carnitine was often cited as underwhelming, showing negligible changes in muscle carnitine content and fat loss outcomes. However, these findings may have been limited by a short study window