A retrospective study demonstrated that anemia was a risk factor for decreased renal function in patients with T2DM with preserved renal function and normal albuminuria, and the trend toward decreased renal function was greater with decreasing Hb levels (OR = 0.69, 95% CI = 0.47–0.99), as demonstrated by the current results. This evidence concerns the gene GSTM1 and type 2 diabetes mellitus.