GSTM1 and anemia (phenotype): More than 30% of patients already have hemoglobin (Hb) levels <12 g/dL by Stage 3 CKD [3] when the estimated glomerular filtration rate (eGFR) falls below 59 ml/min/1.73 m2, and many patients develop anemia before their CKD is diagnosed [3,4].