L Carnitine Injection VolusiaMedicalCenter Subcutaneous Injection Sites and Instructions for Safe Self Administration How to Self Administer Subcutaneous & Intramuscular Injections 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