Dr. prescribed B12 injections. Pharmacy only gave me vials. Where do you get your needles and syringes? What size?? Where do I inject? : r B12_Deficiency Know Your Needles A Quick Nursing Guide! , Today, lets understand the different types of needles and their clinical purposes , Green Needle (21G) For IM injections like vaccines or Medsitis' Guide To Syringes & Needles. 12 Week Steroid Injection Cycle Pack BD Needles, 2ml Syringes & Swabs 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 How to self inject intramuscular vitamin B12 Overview Guy's and St Thomas' NHS Foundation Trust