Know Your Needles A Quick Nursing Guide! Today, let's understand the different types of needles and their clinical purposes Green Needle (21G) For IM injections like B12 Shots Richardson Weight Loss Richardson Vitamin B12 Injections 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 Injecting B12 Enhance Me Training Academy