Characteristics of non-cobalamin deficient patients who receive regular cyanocobalamin injections.

For decades Vitamin B12 injections have been administered to patients with no documented deficiency. A previous study identified a cohort of patients who described vitamin B12-responsive symptoms despite lack of cobalamin deficiency as measured by conventional laboratory tests. These patients have been studied further and, when compared with controls, were found to have had more prescriptions for psychoactive drugs (P less than .