C4B and type 2 diabetes mellitus: In this study, we discovered that the course of T2DM, smoking history, BMI and FBG, DR, HbA1c, TC, TG and LDL-C levels were common risk factors for T2DM, and as the course of T2DM was prolonged, FBG levels increased, DR staging worsened, HbA1c accumulated, and CH and CRF values gradually decreased.