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 10 Week Injection Cycle Kit: Syringes & Needles & Alcohol Wipes only 5.22 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 B12 Injections at Allura Skin, Laser & Wellness Clinic