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 Choosing wisely: needle length and gauge considerations for intramuscular and subcutaneous injections A Guide to Needle and Syringe Choices Is this the right size needle for im injections? : r B12_Deficiency B12 Shots Needle Size