Needle Size for B12 Injection: 5 Must Know Tips Purchase Needles (PrecisionGlide) 1 inch or 1 2 inch at BiosenseClinic BiosenseClinic CA Understanding Needle Gauges and Injection Sites If youre still guessing needle sizes were not doing that in 2026 , Heres what you MUST know:, Smaller gauge number = BIGGER needle, 1820G = blood & trauma, 2123G = IM, 2527G = 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 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