Maybe you mean B6, which is associated with small fiber neuropathy.

B12 has to jump through a number of hoops before it‘s even converted into a usable form [1].

I‘m sure you‘re meaning well, but B12 deficiency is a wide spread problem [2], and it’s questionable that excess is worse than deficiency.

1: https://pubmed.ncbi.nlm.nih.gov/19832808/#&gid=article-figur...

2: https://pmc.ncbi.nlm.nih.gov/articles/PMC7792587/

EDIT: After posting, I saw your other comments. Maybe you can update parent.