Studies on the Minimum Daily Requirement for Vitamin B12

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 . . .