are you anemic? or have you been?
altho my only medical training involved handwriting (mine is indecipherable and should have more than made me eligible for harvard med), anemia (and the accompanying lack of energy) would be one of the few legitimate uses of injectible b-12 of which im familiar.
in the 60s, injections of b-12 were a minor fad (encouraged, i believe, by reports about jfk and celebrities recieving them--even tho it turned out the park ave dr feelgood who was that year's doc to the stars was actually shooting them up with a cocktail including a substantial amoung of amphetamine). i knew people who swore by b-12 injections as an instant hangover cure (ive never seen any reliable literature to back that claim tho). everytime ive wandered into one of the frontera border towns (laredo, tijuana, etc.), ive seen signs advertising clinics offering b-12 injections.
if it were me and i wasnt anemic, id get a second opinion. it might turn out that im totally mis- or uninformed, but better to find that out up front right?