Objective: To evaluate the use of oral cyanocobalamin therapy in the treatment of cobalamin (vitamin B(12))-deficient anemia.

Data sources: Primary and review articles were identified by MEDLINE search (1966-May 2000) and through secondary sources.

Data synthesis: Cobalamin-deficient anemia is among the most common diagnoses in older populations. Cobalamin-deficient anemia may be diagnosed as pernicious anemia, resulting from the lack of intrinsic factor required for cobalamin absorption or as protein malabsorption from the inability to displace cobalamin from protein food sources. Several studies provide evidence that daily oral cyanocobalamin as opposed to monthly parenteral formulations may adequately treat both types of cobalamin-deficient anemias.

Conclusions: Daily oral cyanocobalamin at doses of 1000-2000 microg can be used for treatment in most cobalamin-deficient patients who can tolerate oral supplementation. There are inadequate data at the present time to support the use of oral cyanocobalamin replacement in patients with severe neurologic involvement.