The B12 Shot: What Every Human Needs to Know About Injectable Vitamin B12 Syringes and Needles Medical Syringes Luer Lock Vitamin B12 Injections Preferred Healthcare B12 Shots Needle Size Does size matter? Historically, a bigger needle gauge was considered better to prevent damage to red blood cells. However, our recent guidelines recommend using smaller gauge needles (2325 G) for all Do You Need a Prescription for B12 Injections? OmegaQuant