Ivy Grove Surgery : Self administration of B12 injection For subcutaneous injections, using shorter needles (4 5mm) is the safest choice to ensure medication stays in the fatty layer and avoids muscle injury. A 4mm needle is ideal, minimizing pain while keeping Best Vitamin B12 Injections Dosage And Frequency PA Relief like, swipe, and save for when it's your turn to do an injection on a patient Intramuscular (IM) Angle: 90 Needle Size: 2225G, 11.5 inch Med Examples: Vaccines (e.g. Tdap, Syringes and Needles Medical Syringes Luer Lock