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Direct answer
A kidney disease progression calculator uses eGFR slope: (now − prior) ÷ (months ÷ 12). Demo 52 → 45 over 18 months → -4.67/yr, stage G3a, linear teaching ~ 3.2 yr to eGFR 30, ~6.4 yr to eGFR 15. Not dialysis timing.
CKD stage (by current eGFR)
G3a
G3a — eGFR 45–59
Annualized eGFR change
-4.67 / year
Negative values mean average loss per year over the window you supplied (or the assumed slope).
Linear teaching projection (not a clinical date)
Rough years to 15 mL/min/1.73 m² if slope stayed constant: 6.4
Rough years to 30: 3.2
If the same straight line continued 5 years: eGFR ≈ 21.7
Linear extrapolation is a teaching simplification. Your nephrology team uses trends, proteinuria, comorbidities, and shared decision-making—not a single projected date.
Educational linear model only. CKD progression is often nonlinear. Dialysis and transplant timing depend on symptoms and labs—not crossing eGFR 15 on a calculator. Always add urine albumin-to-creatinine ratio with your clinician.
| Scenario | Mode | ΔeGFR/yr | G-stage | To 30 | To 15 | eGFR @ 5y |
|---|---|---|---|---|---|---|
| Default — eGFR 52→45 over 18 months | Two labs | -4.67 / yr | G3a | ~3.2 yr | ~6.4 yr | 21.7 |
| Slow decline — 72→68 over 24 months | Two labs | -2 / yr | G2 | ~19 yr | ~26.5 yr | 58 |
| Assumed −3/yr — current eGFR 38 | Assumed decline | -3 / yr | G3b | ~2.7 yr | ~7.7 yr | 23 |
| Rapid — 35→22 over 12 months | Two labs | -13 / yr | G4 | — | ~0.5 yr | 5 |
| Stage | eGFR (mL/min/1.73 m²) | Teaching meaning |
|---|---|---|
| G1 | ≥90 | Normal or high; kidney damage may still exist (albuminuria, hematuria, imaging) |
| G2 | 60–89 | Mildly decreased; monitor trend and cardiovascular risk |
| G3a | 45–59 | Mild to moderate decrease; many guidelines discuss nephrology co-management |
| G3b | 30–44 | Moderate to severe; medication dosing and complication screening intensify |
| G4 | 15–29 | Severe; prepare for renal replacement therapy education when appropriate |
| G5 | <15 | Kidney failure range; dialysis/transplant decisions are clinical, not formula-based |
This progression tool uses eGFR only. Ask your clinician for urine ACR on the same lab requisition as creatinine.
| Category | Urine ACR | Progression context |
|---|---|---|
| A1 — Normal to mildly increased | <30 mg/g | Lower progression risk when eGFR stable |
| A2 — Moderately increased | 30–300 mg/g | Moderate risk; ACEi/ARB and BP targets often emphasized |
| A3 — Severely increased | >300 mg/g | Higher progression and cardiovascular risk—needs specialist input |
| Slope (approx.) | How teams often frame it |
|---|---|
| 0 to −2 mL/min/1.73 m²/yr | Relatively slow in many cohorts—still monitor cause and albuminuria |
| −2 to −5 | Common “moderate” decline range in teaching examples—therapy may bend curve |
| −5 to −10 | Faster decline—often warrants expedited evaluation and adherence review |
| < −10 | Rapid loss—exclude AKI on CKD, obstruction, relapse; urgent nephrology context |
Annualized ΔeGFR = (eGFR_now − eGFR_prior) ÷ (months_between ÷ 12)
If ΔeGFR < 0 and current > target: years_to_target ≈ (current − target) ÷ |ΔeGFR|
The calculator answers three teaching questions: (1) What G-stage is this eGFR today? (2) What was the average yearly change between two labs? (3) If that straight line continued, when would eGFR cross 30 or 15? Step 3 is the least clinically reliable but helps students understand why a −4.7 mL/min/1.73 m²/year slope feels “faster” than −2.
Estimate a single eGFR first with our GFR calculator, then return here when you have two comparable timed results.
Stage: G3a — eGFR 45–59
Annualized change: -4.67 mL/min/1.73 m² per year
Linear teaching horizons: ~3.2 years to eGFR 30, ~ 6.4 years to eGFR 15; eGFR in 5 years ≈ 21.7 if slope unchanged
Linear extrapolation is a teaching simplification. Your nephrology team uses trends, proteinuria, comorbidities, and shared decision-making—not a single projected date.
Share for nephrology and primary care teaching
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