L Carnitine Injectable Factor Health MD Subcutaneous Injection Sites and Instructions for Safe Self Administration 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 Subcutaneous Injection: What It Is and How to Give One Injectable L Carnitine for Slimming: Does It Really Work? National Medical Resources Inc