how long before b12 injections take effect Quickly Does a Shot Work? What to Expect How Fast Does a Vitamin
Description
Administration frequency varies based on deficiency severity and individual response

If I have any of this wrong, feel free to correct me (addressing more experienced members of this forum) The problem with a retest at this point is that after 6 injections, the B12 level will likely be elevated and it will be very difficult to know what the original value would have been
References Kraus D, et al

Dont be surprised if you dont see a trace of blood, says Foxx

No, clinical trials definitively demonstrated that AOD-9604 has no effect on serum IGF-1 levels

Some things to consider
