I do not have a B12 deficiency but my doctor said he didn't have a problem with my taking B12 supplements. I just haven't had the time to go get some. BUT you do have to be careful. These vitamins and supplements can hurt you...especially if you don't need them. You might get good results with the supplements and not the shots.
Here is a good link to see how vitamin B12 can help.
http://www.mayoclinic.com/health/vitamin-B12/NS_patient-vitaminb12/DSECTION=evidence
Sherrine