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 B12 Shots at Home: How, Where & How Often to Inject Yourself AZ IV Medics Injecting B12 Enhance Me Training Academy Vitamin B12 Injections for Energy Support Vitamin Injection (IM Shot) Dr. Revive IV Therapy & Pain Clinic.