- Last Update On : 2014-02-02
Vitamin B12, which is also called cyanocobalamin, is a coenzyme synthesized by microorganisms that is required for nucleic acid synthesis. It is released after protein digestion and bound to intrinsic factor in the stomach. The intrinsic factor‑Vitamin B12 complex is then rapidly absorbed in the ileum. Once absorbed, Vitamin B12 is transported in the blood by transcobalamin 1, which is released by granulocytes. The daily requirement for Vitamin B12 is approximately 2 to 5 ug and the total body stores are approximately 2 to 5 mg.
Vitamin B12 measurement is useful in the evaluation of patients with macrocytic anemia (MCV above 100), motor and/or sensory neuropathies, and unexplained neuropsychiatric symptoms. Some patients with B12 may not present with macrocytic anemia because it is masked by a coexisting disorder such as iron deficiency or thalassemia.
The most common cause of vitamin B12 deficiency is pernicious anemia, which is charact