IM Injections Olympia Pharmaceuticals How to self administer subcutaneous B12 injection., 1. Withdraw proper dosage from vial into an insulin syringe, 2. Clean site of injection (abdomen or other proper site), 3. Pinch the skin where you Subcutaneous injecting WithYou 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 Sites of Administration of Subcutaneous injection