When my mother was diagnosed with Vit B12 deficiency two or three years ago her level was 140 pmol/L which is approx 189 pg/ml. She was started on Neocytamin B12 injections three monthly right away and it fixed her immediately.......even though she had had symptoms for several months before the diagnosis.

So what I can't quite understand are the discussions which talk about PN getting worse before it gets better once Vit B12 treatment has commenced! Can someone tease that out a bit more for me please?

Also if the PN persists (in cases of PN of unknown cause) despite Vit B12 supplementation then what's the scientific basis to continue it -assuming levels are at a reasonable level?