Whether a patient with diabetic nephropathy needs a biopsy depends on the condition of the patient. Firstly, if the kidney disease is in the early stages and the blood creatinine level has not exceeded 256 micromoles per liter, a kidney biopsy can be considered. Otherwise, if the blood creatinine level exceeds 256 micromoles per liter, a biopsy is no longer meaningful since significant fibrosis and hardening of kidney tissue have already occurred. At this point, if it is unclear whether the proteinuria is caused by diabetes or another disease, a kidney biopsy can be considered to diagnose the cause and extent of glomerular damage, and to provide a basis for treatment.