Thanks for all the replies. We've not had the appointment with the specialist yet, mum is due to have memory tests tomorrow morning.
It's interesting that it's seems to be treated by injections rather than a pill supplement. It seems incredible to think a deficiency of one vitamin can make you crazy. I wish they routinely checked for it in the elderly given that they know it could be a problem.
As for how much meat, how can you tell what a portion is. I wonder if we've been eating too little meat because we would make 3 chicken breasts do 6 meal portions and now I'm wondering if that is too little. Mum eats very little red meat, the occasional beef, bacon or ham and no liver. She does take cod liver oil and glycosamine as supplements for arithritis.
I am so glad I pestered the doctor now because I've noticed mums behaviour has been strange for at least a year, my dad recons longer. If mum had had a B12 test in with her regular blood test, they may have picked it up sooner. I dread to think what she would have been like if we'd left it any longer. I just hope its not done too much damage. I do occasionally seem glimpses of the old mum even on her bad days.