GSTM1 and chronic kidney disease: Consistent with this, and beyond the area of CKD, a pooled analysis of data from the oral iron control arm of five randomized studies in patients with anemia of various etiologies (e.g., postpartum, heavy uterine bleeding, gastrointestinal disorders), reported in abstract form only, found that among patients without an Hb increase ≥ 1 g/dL after 2 weeks of oral iron therapy, 38.8% achieved a response after a switch to IV iron compared to only 10.2% who continued oral iron [18].