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 Vitamin B12 Injections 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 Vitamin B12 Injection Dosage for Adults: 7 Key Facts & Guidelines Liv Hospital B12 Shots Richardson Weight Loss Richardson Vitamin B12 Injections How Needle Gauge Affects Injection Comfort & Efficacy