(1) If the duration of diabetes mellitus is short, non-diabetic renal impairment in combination with diabetes mellitus should be excluded; (2) The incidence and degree of hypertension in patients with non-diabetic renal impairment in combination with diabetes mellitus are lower than in patients with diabetic nephropathy, especially in the presence of large amounts of proteinuria or renal insufficiency, if the blood pressure is not high, non-diabetic renal impairment in combination with diabetes mellitus should be excluded; (3) Renal failure caused by diabetic nephropathy is chronic, if acute renal failure occurs (4) Glomerulogenic hematuria is not prominent in patients with diabetic nephropathy, if there is significant hematuria or even carnivorous hematuria, it suggests the presence of non-diabetic nephropathy; (5) Patients with diabetic nephropathy mostly have parallel damage to other target organs, such as retinopathy, if there is no retinopathy, non-diabetic nephropathy should be excluded (6) Diabetic patients with massive proteinuria and stable renal function for a long time.