Needle Sizes Explained: Choosing the Right Gauge for Different Injections B12 Injection sites + How to use B12 Shots Safely Is this the right size needle for im injections? : r B12_Deficiency Ivy Grove Surgery : Self administration of B12 injection How To Give B12 Injection + Benefits 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