The Role of Endoscopy and Colonoscopy in the Evaluation of Low Ferritin Levels and Iron Deficiency Anemia

Iron deficiency and iron deficiency anemia (IDA) are common hematological abnormalities with diverse causes, including inadequate dietary intake, increased physiological requirements, impaired absorption, and chronic blood loss. Low serum ferritin is a key indicator of depleted iron stores, although interpretation may be complicated by inflammation and chronic disease. In adults, persistent or unexplained iron deficiency raises concern for gastrointestinal pathology because chronic occult gastrointestinal bleeding may occur without visible blood loss or prominent digestive symptoms. Upper gastrointestinal endoscopy and colonoscopy have therefore become central components of diagnostic assessment, particularly in men, postmenopausal women, older adults, and patients with recurrent or severe IDA. Upper endoscopy allows direct evaluation of the esophagus, stomach, and duodenum and may identify erosive gastritis, peptic ulcer disease, gastric malignancy, vascular abnormalities, and mucosal disorders associated with impaired iron absorption. Colonoscopy permits assessment for colorectal carcinoma, adenomatous polyps, inflammatory bowel disease, angiodysplasia, and other lower gastrointestinal sources of chronic bleeding. Celiac disease and Helicobacter pylori infection also warrant consideration because iron depletion may develop through altered absorption or chronic mucosal disease. The diagnostic yield of endoscopic investigation varies according to age, sex, hemoglobin and ferritin concentrations, gastrointestinal symptoms, medication exposure, family history, and underlying comorbidities. Identification of gastrointestinal pathology can substantially modify clinical management by directing treatment toward the underlying cause rather than relying exclusively on iron replacement. When bidirectional endoscopy is unrevealing and iron deficiency persists or recurs, evaluation of the small bowel, particularly with capsule endoscopy, may detect vascular, inflammatory, ulcerative, or neoplastic lesions inaccessible to conventional procedures. Appropriate risk stratification remains essential because endoscopy is invasive and carries procedural burdens and potential complications. Timely investigation of patients with unexplained IDA supports early recognition of clinically significant gastrointestinal disease while allowing the intensity and extent of diagnostic assessment to be matched to individual risk.