An article in the New England Journal of Medicine from 1988 drew the attention to a scant discerned problem: neuropsychiatric disorders due to vitamin Biz (cobalamin) deficiency occured in patients, mainly elderly, who didn't present with hematological deviations.1 After administration of vitamin Bi2, the symptoms disappeared in practically all patients. The research demonstrated that in daily practice a deficiency of vitamin B12 is often not recognized as the cause of severe and frequently occuring psychiatric disorders. Advanced research confirmed these results.2 Other research points out the danger of undiagnosed vitamin B12 deficiency, especially in pernicious anaemia.