All 15 children (15/27, 56%) in the low-dose group, who met the new WHO anemia definition at the age of 6-23 months of Hb < 10.5 g/dL, had an Hb response ≥ 1.0 g/dL, with a median Hb response of 2.2 g/dL.<h4>Conclusion</h4>An iron dose of 1 mg/kg/day was as effective as 15 mg/day (median: 1.8 mg/kg/day) in the Hb response. The gene discussed is GSTM1; the disease is anemia (phenotype).