Lets do my first B12 injection together This is something Ive been nervous about for a long time, but today I finally did itand it honestly wasnt bad at all. I used the Union Medico needle guide B12 Injection Dosage and Frequency: 7 Essential Guidelines for Adults Liv Hospital Vitamin B12 Shots in Pharr, TX for Energy Boost B12 Injection Every 3 Months 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.