What are the stages of Chronic Kidney Disease (CKD)?

Chronic Kidney Disease Stages

Chronic kidney disease is classified into five stages based on glomerular filtration rate (GFR), with Stage 3 further subdivided into 3a and 3b, and complete staging requires incorporating both GFR category and albuminuria category (the CGA classification system) rather than GFR alone. 1, 2

The Five CKD Stages by GFR

Stage 1: GFR ≥90 mL/min/1.73 m²

• Requires evidence of kidney damage (albuminuria, proteinuria, or structural abnormalities on imaging) since GFR is normal 1, 2
• Focus on diagnosis and treatment of underlying conditions, slowing progression, and cardiovascular disease risk reduction 2

Stage 2: GFR 60-89 mL/min/1.73 m²

• Requires evidence of kidney damage (cannot diagnose on GFR alone) 1, 2
• Emphasize estimating progression rate of kidney disease 2

Stage 3: GFR 30-59 mL/min/1.73 m²

• Stage 3a: GFR 45-59 mL/min/1.73 m² 1, 2
• Stage 3b: GFR 30-44 mL/min/1.73 m² 1, 2
• This subdivision is driven by data demonstrating different outcomes and risk profiles between these GFR ranges, particularly regarding cardiovascular mortality, acute kidney injury risk, and CKD progression 1
• Begin evaluation and treatment of complications 1, 2
• Risk of complications (hypertension, anemia, hyperphosphatemia) increases significantly below GFR of 60 mL/min/1.73 m² 1, 2

Stage 4: GFR 15-29 mL/min/1.73 m²

• Severe decrease in kidney function 1, 2
• Requires intensive management of complications and preparation for possible kidney replacement therapy 1, 2
• Hypertension prevalence approaches 80% at this stage 1
• All patients with Stage 4 CKD should be referred to nephrology 2

Stage 5: GFR <15 mL/min/1.73 m² or dialysis

• Kidney failure 1, 2
• Kidney replacement therapy (dialysis or transplantation) required if uremic symptoms develop 1, 2

Critical Diagnostic Requirements

Persistence Criterion

• Abnormal GFR or kidney damage must persist for at least 3 months for accurate CKD diagnosis 1, 3

GFR Estimation Method

• Use the CKD-EPI equation for reporting estimated GFR in adults from serum creatinine calibrated to isotope-dilution mass spectrometry reference method 1
• The CKD-EPI equation demonstrates less bias than the MDRD equation, especially at GFR ≥60 mL/min/1.73 m², with improved precision and greater accuracy 1
• Never rely on serum creatinine alone—always use prediction equations that account for serum creatinine, age, sex, race, and body size 1

Albuminuria Categories (Essential for Complete Staging)

• A1: Normal to mildly increased albuminuria 1
• A2: Moderately increased albuminuria 1
• A3: Severely increased albuminuria 1
• An albuminuria level of 30 mg/g represents more than 3 times the normal value in young adults and independently predicts increased risk for CKD complications, cardiovascular mortality, and progression to kidney failure 1

Common Pitfalls to Avoid

Do not classify using GFR alone—use the complete CGA system (Cause, GFR category, Albuminuria category) to avoid incomplete staging and inadequate risk stratification 1

In Stages 1 and 2, evidence of kidney damage (such as albuminuria) is required for CKD diagnosis, while Stages 3-5 can be diagnosed based on GFR alone 1

Do not dismiss age-related GFR decline as "normal aging"—decreased GFR in the elderly remains an independent predictor of adverse outcomes 2

The combination of GFR and albuminuria provides better risk stratification for disease progression and outcomes than either measure alone 1, 3