Investigation of macrocytic anemia Workup of deficiencies seen in megaloblastic anemiasVitamin B12 is necessary for hematopoiesis and normal neuronal function. This assay is useful for investigating Macrocytic anemia and as a workup of deficiencies seen in Megaloblastic anemia. B12 deficiency may be due to lack of intrinsic factor secretion by gastric mucosa (gastrectomy, gastric atrophy) or intestinal malabsorption (ileal resection, small intestinal diseases) leading to Macrocytic anemia.