Vitamin B12 Deficiency Presenting as Anemia and Functional Decline in an Older Adult: A Case Report.

Anemia is a common condition in older adults and is associated with increased morbidity, geriatric syndromes, and functional decline. We report the case of an 86-year-old woman who presented with severe anemia accompanied by neurologic, hematologic, and oral manifestations, in whom vitamin B12 deficiency was identified as the underlying etiology. Following targeted parenteral cyanocobalamin therapy, the patient demonstrated marked hematologic recovery and substantial improvement in gait, strength, and independence in basic activities of daily living, as documented through a comprehensive geriatric assessment. This case underscores the importance of recognizing vitamin B12 deficiency as an underdiagnosed yet reversible cause of anemia and functional deterioration in older adults and highlights the essential role of comprehensive geriatric assessment in detecting reversible contributors to frailty and enabling timely, individualized intervention.