How to Give a B12 Injection: Step By Step Instructions B12 Injection sites + How to use B12 Shots Safely Injection Sites Quick Revision for Nursing Students Understanding the correct injection site is essential for safe medication administration. Intramuscular (IM) Injection Sites Deltoid Vastus Lateralis Ventrogluteal 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 How to Give a B12 Injection: Step By Step Instructions