what size needle do you use for b12 injections at Home - Safety Guide Self-Administration B12 vitamin Store Needle and
Description
In case you missed that day in biology, the Intrinsic factor is a glycoprotein that binds to vitamin B-12 so that you can absorb it directly into the blood

Its possible, as with any vaccine, excessive use of alcohol has the potential to increase side effects and reduce the immune systems response to the vaccine

LCD was revised and announced on 2/2/19 2021 with effect from 1st January 20201

That's in addition to, as mentioned by Gambit, excess alcohol causing issues with the liver which is the primary bodily store of B12
