Notes that vitamin B12 deficiency is a multifaceted, multisystem disorder that becomes more common with advancing age. Insufficient absorption seems to be the pathologic mechanism underlying most cases of B12 deficiency in the elderly. It is associated with an increased morbidity if it goes undetected, as often happens. Its diagnosis can be enhanced if the clinician recognizes the nonspecific symptoms, glossitis, dermatological, and neuropsychiatry abnormalities. It is highly important to realize the nature of vitamin B12 deficiency in the elderly. It is a continuum from negative B12 balance to frank deficiency, which can be detected by low serum B12 levels long before changes occur in hemoglobin levels. Since signs and symptoms of this complaint can be ill-defined, the clinician should be concerned about occult B12 deficiency in older Ss with baffling weakness, fatigue, unusual neurologic findings, or cognitive dysfunction. A greatly discussed issue is the relationship between B12 deficiency and dementiMany investigators think that is has not been established as a cause of reversible dementiCurrent findings in the literature propose that treatment may prevent significant neurologic and/or hematologic disease.