Hello and Welcome to the Pain Management Forum. I am sorry to hear about your sharp shooting pain. We can relate.
My guess is that your pain is not associated with oral ingestion of Vit B12. However Vit B12 should be injected for proper absorption.... so my question is has your PCP prescribe this in injection form and was the B12 injected? If so the injection needle could have struck a nerve and that may be the cause of the shooting pain.
Sharp shooting pain usually originates from a nerve(s).... Hence my suggestion that an oral ingestion of B12 would not cause this pain.
I suggest that you consult your PCP. He/she will have the best and most accurate information for you. Please keep in touch and let us know how you are doing.
Take Care,
~Tuck
Doesn't sound right at all. Talk to your dr. about adverse symptoms to taking the B12. You may need an adjustment or a different drug. Good luck to you.