B12 Shots at Home: How, Where & How Often to Inject Yourself AZ IV Medics How to Use These 4 IM Injection Spots Safely How to Self Inject Vitamin B12 at Home The Sanctuary Wellness Institute Subcutaneous Injection: What It Is and How to Give One Common IM Injection Sites Deltoid (Upper Arm) Location: About 23 finger widths below the acromion process (shoulder bone). Best for: Vaccines and small volume injections (1 mL). Notes: Easy to access but limited