Subcutaneous Injection Sites and Instructions for Safe Self Administration Buy L Carnitine Injections Online The HCG Institute How to Self Administer Subcutaneous & Intramuscular Injections Subcutaneous Injection Sites and Instructions for Safe Self Administration 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