Failure to absorb the vitamin from the intestine leads to pernicious anemia. Pernicious anemia is an autoimmune disorder (antibodies attack the parietal cells) where the intrinsic factor is deficient.

Patients are usually anemic but later on show neuropsychiatric symptoms.

Significant amounts of B12 are stored in the body (4-5mg)

It may take several years for deficiency to develop as a result of partial gastrectomy.

Pernicious anemia occurs when intrinsic factor is deficient.