Where do you obtain your injections? What company supplies it to you?
Do you get them from the doctor?

Are they compounded for you?

When a therapy fails one has to consider the drug or route of administration
is faulty, perhaps.

I once researched B12 injection. The cyano version is cleared from the serum in 72 hrs in normal people.

With your high doses, some should be in the serum, unless you are excreting it thru the kidneys at a high rate for some reason.

So I would look to the supplier of your injections. Maybe there is nothing in there? or it is subpotent?

What would happen if you subsitituted 5mg methylcobalamin ORAL daily for a while? I wonder.