Subcutaneous Injection: What It Is and How to Give One L Carnitine Injections: A Clinical Guide for Practitioners National Medical Resources Inc L Carnitine Injectable Factor Health MD 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 INJECTION How to Self Administer Subcutaneous & Intramuscular Injections