BACKGROUND Iron deficiency is a major postoperative complication of Roux-en-Y gastric bypass surgery. Oral replacement can fail to correct the deficiency. Thus, recourse to parenteral iron administration might be necessary. Our objective was to evaluate the effectiveness and safety of a standardized 2 g intravenous iron dextran infusion in the treatment of iron deficiency after Roux-en-Y gastric bypass surgery. The setting was a university-affiliated community hospital in the United States. METHODS We reviewed the medical records of 23 patients at our institution who had received 2 g of iron dextran intravenously for recalcitrant iron deficiency after Roux-en-Y gastric bypass surgery. We obtained the demographic data and the complete blood count and serum iron studies obtained before treatment and at outpatient visits after infusion. RESULTS Before treatment, all 23 patients were iron deficient (average ferritin 6 ng/mL) and anemic (average hemoglobin 9.4 g/dL). By 3 months, the average ferritin and hemoglobin had increased to 269 ng/mL and 12.3 g/dL, respectively. The hemoglobin levels remained stable throughout the follow-up period. The iron stores were adequately replaced in most patients. Four patients required a repeat infusion by 1 year, because the ferritin levels had decreased to <15 ng/mL. The probability of remaining in an iron replete state was 84.6% (95% confidence interval 78-91.2%). One patient required warm compresses for superficial phlebitis. No other significant adverse events were reported. CONCLUSIONS Intravenous administration of 2 g of iron dextran corrects the anemia and repletes the iron stores for ≥1 year in most patients. This therapy is safe, tolerable, efficient, and effective.