How often should vitamin B12 injections be administered and how frequently should laboratory monitoring be performed? FREE B12 injections the month of October no purchase necessary. 1 per a person. This is to show appreciation to our customers. It also allows new clients the opportunity to try vitamin B12 Shots in Friso, Sherman, Anna. and Sunnyvale, TX B12 Shots Phoenix Arcadia, Scottsdale, Tempe & Glendale A little insight to the importance of the b12 injections. My client hadn't been feeling well & had some bloods done with her GP. The results identified a severe deficiency in b12.