C3 and diabetic kidney disease: After balancing covariates including age, gender, SBP, HbA1C, TG, and UACR between the G2-G5 and control groups, per 0.1 g/L increment in serum C3 was significantly associated with a 27.8% reduced risk of DKD at G5 stage (OR, 95% CI, P: 0.722, 0.616-0.847, <0.001) relative to the G1 stage.