Studies on the Minimum Daily Requirement for Vitamin B12

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Abstract
THE minimum daily adult requirement for vitamin B12 has not been established.1 Shortly after the isolation of crystalline vitamin B12 in 1948 by Rickes et al.,2 West and Reisner3 reported that the minimum effective parenterally administered dose for patients with pernicious anemia was 1 microgm. daily. Noting that these investigators had not obtained a reticulocyte response to 0.1 microgm. of cyanocobalamin daily in the only patient given this dose, Darby and his associates4 found that parenteral administration of cyanocobalamin, in doses of 0.25 to 1.0 microgm. daily, to patients with pernicious anemia in relapse resulted in reticulocyte responses . . .