Gastrointestinal blood loss is the primary cause of iron deficiency anemia in older adults. Bidirectional endoscopy (combined colonoscopy and esophagogastroduodenoscopy) is highly sensitive and specific in its ability to locate gastro-intestinal lesions resulting in iron deficiency anemia. Although the diagnostic yield of esophagogastroduodenoscopy is higher than that of colonoscopy, the possibility of malignant disease dictates that initial colonoscopy be performed in all but a few cases involving distinct upper gastrointestinal risk factors and symptoms. If neither colonoscopy nor esophagogastroduodenoscopy identifies a source of blood loss, a safe course is to observe the patient and provide supplemental iron. Patients who fail to respond to supplemental iron or who become transfusion-dependent require further evaluation. Small-bowel evaluation has a role in selected patients.