CKD GFR Stage Calculator (G1–G5)

Q: Does a low eGFR always mean chronic kidney disease?

Only if it persists. A single reading below 60 mL/min/1.73 m² can reflect dehydration, acute illness or a recent change in medication. CKD requires the abnormality, or a damage marker, to be present for more than three months.

Q: What is the difference between G3a and G3b?

G3a covers 45–59 mL/min/1.73 m² and G3b covers 30–44. They were split from a single 'moderate' category because cardiovascular risk and the rate of progression to kidney failure differ meaningfully between the two.

Q: Is G1 or G2 with no albuminuria still CKD?

No. Without a damage marker persisting beyond three months, an eGFR of 60 or above is a normal or near-normal result, not chronic kidney disease. Labelling it as CKD overstates the finding.

Q: When should a patient be referred to nephrology?

Common triggers include G4 or G5, a rapid fall in eGFR, heavy albuminuria (A3) alongside a reduced eGFR, or uncertainty about the cause. Local referral criteria vary and should be checked against KDIGO's risk-based thresholds.

Place an eGFR into its KDIGO G1–G5 category, and see why a normal-range result is not, by itself, a diagnosis of chronic kidney disease.

Last updated 31 Aug 2026

CKD GFR Stage (G1–G5)

eGFR → G-stage

eGFR (mL/min/1.73 m²)

G3aExample

eGFR 48 mL/min/1.73 m²

KDIGO GFR categories (G1–G5)

G1 ≥90 · G2 60–89 · G3a 45–59 · G3b 30–44 · G4 15–29 · G5 <15 (mL/min/1.73 m²)

G1 / G2: CKD only when a damage marker persists beyond three months — not from the eGFR alone
G3a / G3b: the eGFR criterion for CKD is met on its own; split because outcomes differ materially between the two
G4: severely decreased; pre-dialysis planning should begin
G5: kidney failure, below 15 mL/min/1.73 m²

Worked example

eGFR 48 mL/min/1.73 m²
48 is below 60 and not below 45 → falls in the 45–59 band
→ G3a, mildly to moderately decreased

GFR categories

G1 and G2 require evidence of kidney damage persisting beyond three months to count as CKD; G3a and below meet the CKD definition from the eGFR value alone.
Stage	eGFR (mL/min/1.73 m²)	Description	Is this CKD alone?
G1	≥ 90	Normal or high	No — needs a damage marker > 3 months
G2	60 – 89	Mildly decreased	No — needs a damage marker > 3 months
G3a	45 – 59	Mildly to moderately decreased	Yes
G3b	30 – 44	Moderately to severely decreased	Yes
G4	15 – 29	Severely decreased	Yes
G5	< 15	Kidney failure	Yes

What a GFR stage does and does not tell you

The KDIGO classification splits estimated glomerular filtration rate into six bands, G1 through G5, each roughly halving the range once G3 is reached. On their own the numbers describe kidney function at a single point in time; they only become a diagnosis of chronic kidney disease when a low eGFR, or evidence of kidney damage, persists for more than three months.

This is the point most often missed. G1 and G2 are not, by themselves, chronic kidney disease. An eGFR of 95 mL/min/1.73 m² with no albuminuria and no structural abnormality is a normal kidney, not early-stage CKD. The diagnosis requires either an eGFR below 60 mL/min/1.73 m², or a marker of damage — albuminuria, persistent haematuria, an abnormal renal ultrasound, electrolyte abnormalities from tubular disorders, or biopsy-proven disease — present for more than three months, whatever the eGFR happens to be. A single low reading, or a normal one in someone with unconfirmed damage, is not enough to stage.

Below G3a, staging tracks risk closely, which is why G3 was split into G3a and G3b: outcomes differ enough between 45–59 and 30–44 mL/min/1.73 m² to change monitoring intensity. G4 and G5 carry a rising probability of needing renal replacement therapy and warrant nephrology involvement if it has not already started. Staging should always be read alongside the albuminuria category, since the KDIGO risk grid shows that outcomes at any given eGFR vary several-fold depending on albuminuria — the two together, not eGFR alone, set monitoring frequency and referral thresholds.

Frequently asked questions

Does a low eGFR always mean chronic kidney disease?

Only if it persists. A single reading below 60 mL/min/1.73 m² can reflect dehydration, acute illness or a recent change in medication. CKD requires the abnormality, or a damage marker, to be present for more than three months.

What is the difference between G3a and G3b?

G3a covers 45–59 mL/min/1.73 m² and G3b covers 30–44. They were split from a single 'moderate' category because cardiovascular risk and the rate of progression to kidney failure differ meaningfully between the two.

Is G1 or G2 with no albuminuria still CKD?

No. Without a damage marker persisting beyond three months, an eGFR of 60 or above is a normal or near-normal result, not chronic kidney disease. Labelling it as CKD overstates the finding.

When should a patient be referred to nephrology?

Common triggers include G4 or G5, a rapid fall in eGFR, heavy albuminuria (A3) alongside a reduced eGFR, or uncertainty about the cause. Local referral criteria vary and should be checked against KDIGO's risk-based thresholds.

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References

KDIGO 2024 Clinical Practice Guideline for the Evaluation and Management of Chronic Kidney Disease. Kidney Int. 2024;105(4S):S117–S314.
Levey AS et al. Nomenclature for kidney function and disease. Kidney Int. 2020;97(6):1117–1129.