A 52-year-old man presents with a 3-month history of fatigue and dyspnea. Laboratory findings: Hb 8.9 g/dL, MCV 78 fL, MCH 24 pg, RBC count 5.8 × 10^12/L, serum iron 95 µg/dL (normal 60–170), ferritin 320 ng/mL (normal 12–200), TIBC 280 µg/dL (normal 250–425). Peripheral blood smear shows microcytic RBCs with target cells and occasional nucleated RBCs. What is the most appropriate next step in management?