Compounded Carnitine (L) Injection Empower Pharmacy 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 Subcutaneous Injection: What It Is and How to Give One L carnitine is an amino acid derivative that plays a crucial role in the bodys energy production processes. As an injectable supplement, L carnitine has been employed to support various health