i don't know why you got it in the first place. if you have pernicious anemia (the reason it is used) then your doctor will need to monitor your levels to see when the next shot is done. this question can only be answered by the person prescribing this therapy to you. if your doctor gave it to you to increase your energy then you just got a vitamin placebo.
how long does a b12 shot last. i've just received a b12 shot from my doctor. how long can i expect the results to last?