Definition: refers to kidney damage or GFR <60ml/min/1.73m2 for 3 months. 1, kidney damage (abnormal kidney structure or function) ≥3 months, may or may not have decreased GFR and may show the following abnormalities: abnormal pathological examination; positive indicators of kidney damage: including abnormal blood or urine composition or abnormal imaging examination; 2, GFR <60ml/min/ 1.73m2 for ≥3 months with or without evidence of renal injury. Table 1 Staging of chronic kidney disease Stage Description Glomerular filtration rate (GFR) Increased risk Risk factors for chronic kidney disease (e.g., diabetes mellitus, hypertension, family history, old age, etc.) 90 or more 1, kidney injury (protein in urine) with normal filtration rate 90 or more 2, kidney injury with mild decrease in filtration rate 60 to 89 3, moderate decrease in filtration rate 30 to 59 4, severe decrease in filtration rate 15 5. Renal failure (requiring dialysis or kidney transplantation) 15 or less International Kidney Foundation Kidney Disease Regression Quality (NKF-K/DOQI) Clinical Behavior Guidelines for Chronic Kidney Disease.