How to Give a B12 Injection: Step By Step Instructions Not all shots are the same here's a guide Injections are a fast, effective way to deliver medications, nutrients, and vaccines directly into the bodybut not all injections are the 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 B12 Shots at Home: How, Where & How Often to Inject Yourself AZ IV Medics