GFR Ranges for CKD Stages
Chronic kidney disease is classified into five stages based on GFR, with Stage 1 requiring ≥90 mL/min/1.73 m² plus evidence of kidney damage, Stage 2 at 60-89 mL/min/1.73 m², Stage 3 at 30-59 mL/min/1.73 m², Stage 4 at 15-29 mL/min/1.73 m², and Stage 5 at <15 mL/min/1.73 m² or requiring dialysis. 1
CKD Stage Definitions
The staging system is based on estimated GFR and requires abnormalities to persist for at least 3 months to establish the diagnosis of CKD 1:
Stage 1: GFR ≥90 mL/min/1.73 m²
- Requires evidence of kidney damage (proteinuria, albuminuria, hematuria, or structural abnormalities) 1
- Normal or increased kidney function but with documented kidney damage 1
Stage 2: GFR 60-89 mL/min/1.73 m²
- Mild decrease in GFR with evidence of kidney damage 1
- Kidney damage must be documented through abnormalities in blood/urine tests or imaging 1
Stage 3: GFR 30-59 mL/min/1.73 m²
- Moderate decrease in GFR 1
- CKD diagnosis can be made based on GFR alone at this stage, regardless of other markers of kidney damage 1
Stage 4: GFR 15-29 mL/min/1.73 m²
- Severe decrease in GFR 1
- Represents advanced kidney disease requiring preparation for renal replacement therapy 1
Stage 5: GFR <15 mL/min/1.73 m²
- Kidney failure 1
- May require chronic dialysis treatment even if GFR is technically in Stage 4 range if uremic symptoms are present 1
- Designated as "5D" when patient is on dialysis or "5T" when patient has received a kidney transplant 1
Critical Clinical Considerations
GFR estimation requires more than serum creatinine alone - prediction equations incorporating age, sex, race, and body size (such as MDRD or CKD-EPI) provide more accurate assessment than creatinine values alone 1. Relying solely on serum creatinine grossly overestimates kidney function, as patients can maintain seemingly normal creatinine levels (e.g., 1.3 mg/dL) despite significantly declining GFR 1.
Stages 1 and 2 require evidence of kidney damage - a GFR above 60 mL/min/1.73 m² alone is insufficient for CKD diagnosis without documented proteinuria, albuminuria, hematuria, pathological abnormalities, or imaging abnormalities 1. Once GFR falls below 60 mL/min/1.73 m² (Stage 3 or higher), CKD can be diagnosed regardless of other markers 1.
The 3-month duration requirement is essential - transient kidney function abnormalities do not constitute CKD; structural or functional abnormalities must persist for at least 3 months to meet diagnostic criteria 1.