A logistic regression analysis model considering age, gender, body mass index, waist circumference, serum creatinine, eGFR, CRP, HbA1c, and fasting blood glucose, along with PNI, showed that PNI was an independent risk factor for diabetic nephropathy in type 2 diabetes mellitus, since a unit decrease in PNI increased the odds of diabetic nephropathy by 1.29 times (p < 0.001, OR: 1.29, 95% CI: 1.25–1.34). This evidence concerns the gene CRP and type 2 diabetes mellitus.