What are the KDIGO CKD G-stages?

By eGFR in mL/min/1.73 m²: G1 is 90 or above (normal/high), G2 is 60–89 (mildly decreased), G3a is 45–59, G3b is 30–44, G4 is 15–29 (severely decreased), and G5 is below 15 (kidney failure).

Is a low eGFR alone enough to diagnose CKD?

For G3a and below, a persistently reduced eGFR is sufficient. For G1 and G2, a normal or mildly reduced eGFR is only classified as CKD when there is also a marker of kidney damage such as albuminuria, haematuria, or a structural abnormality.

How is the eGFR confirmed as chronic?

Chronicity requires the abnormality to persist for at least three months. A single reduced eGFR should be repeated on a sample taken at least 90 days later before labelling the patient with chronic kidney disease.

When should I refer to nephrology?

Referral is generally indicated for G4 and G5, rapidly declining eGFR, significant or rising albuminuria, resistant hypertension, recurrent stones, or a hereditary kidney disease. Earlier referral may be appropriate with heavy proteinuria.

Why does the albuminuria category matter?

Full KDIGO classification combines the G-stage with an albuminuria category (A1 below 3, A2 3–30, A3 above 30 mg/mmol ACR) to give a heat-map of cardiovascular and kidney risk. Two patients with the same eGFR can have very different prognoses depending on albuminuria.

What is the GFR-Based CKD Staging Tool?

Free CKD staging tool. Enter an eGFR value to map it to KDIGO chronic kidney disease G1–G5 staging, with clinical guidance on monitoring intervals, drug adjustments, and nephrology referral thresholds. Runs entirely in your browser. It runs free in your browser on Gera Tools, with nothing uploaded.

GFR-Based CKD Staging Tool

Name: GFR-Based CKD Staging Tool
Creator: Gera Tools
License: https://creativecommons.org/licenses/by/4.0/

The GFR-based CKD staging tool maps any estimated glomerular filtration rate (eGFR) to its KDIGO chronic kidney disease G-stage and surfaces the practical implications — how often to monitor, which drugs to adjust, and when to refer. It is built for GPs, nephrologists, and pharmacists.

How it works

KDIGO divides kidney function into six bands by eGFR in mL/min/1.73 m²:

eGFR (mL/min/1.73 m²)	Stage	Description
90 or above	G1	Normal or high
60–89	G2	Mildly decreased
45–59	G3a	Mildly to moderately decreased
30–44	G3b	Moderately to severely decreased
15–29	G4	Severely decreased
Below 15	G5	Kidney failure

Enter the eGFR and the tool returns the matching stage, highlights it in the reference table, and shows stage-specific clinical guidance.

Reading the result and acting on it

The guidance scales with severity:

G1 and G2: Unless a marker of kidney damage is present (albuminuria, haematuria, structural change), these stages do not constitute CKD. Management focuses on cardiovascular risk reduction, blood pressure control, and addressing reversible causes. Annual eGFR review is appropriate.

G3a: The stage where clinical attention typically begins in earnest. Review renally-cleared medications: metformin should be reviewed at G3a and reconsidered at G3b, DOACs need dose-adjustment checks, and gabapentinoids accumulate with lower clearance. Screen for anaemia of chronic kidney disease and mineral-bone disorder. Review frequency typically increases to every 6–12 months.

G3b: Tighter monitoring, more aggressive risk-factor control, and consideration of nephrology involvement for rapidly declining or complex cases. Ensure patients have had dietary advice appropriate to their stage.

G4: This stage typically triggers nephrology referral for preparation for renal replacement therapy (RRT) — whether transplant listing, fistula formation for haemodialysis, or peritoneal dialysis education. Even when not yet symptomatic, earlier referral means better-prepared patients and less emergency dialysis initiation.

G5: Kidney failure. If not on RRT or managed conservatively, urgent nephrology involvement is needed.

Why eGFR alone is not enough for G1 and G2

A single eGFR of 75 or 85 does not diagnose CKD by itself. KDIGO requires either:

A persistently reduced eGFR (below 60) confirmed on two samples at least 90 days apart, or
An eGFR of 60 or above plus a marker of kidney damage such as albuminuria (ACR above 3 mg/mmol), haematuria of renal origin, or an abnormality on imaging or biopsy.

This prevents over-diagnosing CKD in patients who have a transiently low eGFR (acute kidney injury, dehydration) or whose baseline is just below 90.

The albuminuria dimension

Full KDIGO staging combines the G-stage with an albuminuria category:

ACR (mg/mmol)	Category	Description
Below 3	A1	Normal to mildly increased
3–30	A2	Moderately increased
Above 30	A3	Severely increased

Two patients at G3a can have dramatically different cardiovascular and renal prognosis depending on whether their ACR is A1 or A3. The combined G-and-A heat-map is the complete KDIGO risk classification. This tool handles the G-staging; the A-category adds an additional layer of risk stratification beyond the scope of eGFR alone.

Important caveats

All logic runs locally in your browser; nothing is sent to a server. This tool is for clinical reference and educational use — it does not replace clinical judgement, local guidelines, or individual patient assessment. eGFR equations (CKD-EPI 2021, MDRD) each have known limitations in extremes of muscle mass, age, and acute illness.