L Carnitine Injections: A Clinical Guide for Practitioners National Medical Resources Inc Intramuscular vs. Subcutaneous Injections: What's the Difference? Intramuscular (IM) shots go deep into the muscle for faster absorption, while subcutaneous (SubQ) injections are placed just under the skin for slower, more sustained L CARNITINE 1 GM 5 ML ( L CARNITINE ) 5 X 5 ML IV USE AMPOULES Subcutaneous Injection Sites and Instructions for Safe Self Administration