For every 1 g/dL rise in Hb, HbA1c fell by 0.16 ± 0.03% on average for iron deficiency anemia and 0.15 ± 0.03% on average for B12-deficiency anemia; however, the degree of anemia also affected HbA1c concentrations. The gene discussed is GSTM1; the disease is anemia (phenotype).