Thank you for your question.
In the vast majority of cases the low levels of vitamin B12 is due to formation of an antibody that is called as antiparietal cell antibody or anti-intrinsic factor antibody.
High levels of antiparietal cell antibodies attack the parietal cells in the stomach which release intrinsic factor which is a factor that is necessary for absorption of vitamin B12.
The intrinsic factor antibody attacks the intrinsic factor which is essential for absorption of vitamin B12 from the intestine.
So any of these antibodies, when positive, will confirm the cause of low vitamin B12.
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