I inject b12 daily or at least every other day for over two years now. I'm lots better by now but have still slight polyneuropathy left. During this time I've experimented with different dosages of folic acid (as well as with methyl folate and folinic acid) but I'm still not sure what works best for me and my nerve pain.
In case you are in a similar situation to me (ED injections and polyneuropathy), how much folic acid do you take?