Kidney function
CKD-EPI 2021 eGFR (creatinine, cystatin C, or both), Cockcroft–Gault creatinine clearance for drug dosing, and KDIGO CKD and AKI staging — from one set of labs.
1Patient
2Labs
3Acute change optional — for AKI staging
How it works
Which number to use
Staging CKD: eGFR (mL/min/1.73 m²). KDIGO 2024 recommends adding cystatin C when creatinine may mislead — extremes of muscle mass, amputation, frailty, high-protein diets, or when a decision hinges on the value. The combined creatinine–cystatin C equation is the most accurate.
Drug dosing: many labels were built on Cockcroft–Gault. KDIGO 2024 suggests eGFR not indexed to body surface area (mL/min) for dosing, especially at extremes of body size. Follow the product label or your pharmacy's protocol when they specify.
Not at steady state: any creatinine-based estimate is invalid while creatinine is changing (AKI). Use it to stage the injury, not to dose.
Equations
CKD-EPI 2021 (creatinine)
142 × min(Scr/κ,1)^α × max(Scr/κ,1)^−1.200 × 0.9938^age × 1.012 [female] · κ 0.7 F / 0.9 M · α −0.241 F / −0.302 MCKD-EPI 2021 (creatinine–cystatin C)
135 × min(Scr/κ,1)^α × max(Scr/κ,1)^−0.544 × min(Scys/0.8,1)^−0.323 × max(Scys/0.8,1)^−0.778 × 0.9961^age × 0.963 [female] · α −0.219 F / −0.144 MCKD-EPI 2012 (cystatin C)
133 × min(Scys/0.8,1)^−0.499 × max(Scys/0.8,1)^−1.328 × 0.996^age × 0.932 [female]Cockcroft–Gault
CrCl = (140 − age) × weight ÷ (72 × Scr) × 0.85 [female]Ideal body weight (Devine): 50 kg (M) or 45.5 kg (F) + 2.3 kg per inch over 60 in. Adjusted weight = IBW + 0.4 × (actual − IBW), used when actual weight is >120% of IBW. BSA (Mosteller) = √(height cm × weight kg ÷ 3600).
KDIGO staging tables
| GFR category | mL/min/1.73 m² | Albuminuria | UACR mg/g |
|---|---|---|---|
| G1 | ≥90 | A1 | <30 |
| G2 | 60–89 | A2 | 30–300 |
| G3a | 45–59 | A3 | >300 |
| G3b | 30–44 | ||
| G4 | 15–29 | ||
| G5 | <15 |
CKD requires abnormality present for >3 months. G1–G2 without markers of kidney damage is not CKD.
AKI (KDIGO 2012): Stage 1 — creatinine 1.5–1.9× baseline within 7 days, or ≥0.3 mg/dL rise within 48 h; or urine <0.5 mL/kg/h for 6–12 h. Stage 2 — 2.0–2.9×; or <0.5 mL/kg/h for ≥12 h. Stage 3 — ≥3.0×, or creatinine ≥4.0 mg/dL, or KRT started; or <0.3 mL/kg/h for ≥24 h, or anuria ≥12 h.
Sources
- Inker LA et al. New creatinine- and cystatin C–based equations to estimate GFR without race. N Engl J Med 2021;385:1737–49.
- KDIGO 2024 Clinical Practice Guideline for the Evaluation and Management of CKD. Kidney Int 2024;105(4S):S117–S314.
- KDIGO Clinical Practice Guideline for Acute Kidney Injury. Kidney Int Suppl 2012;2:1–138.
- Cockcroft DW, Gault MH. Prediction of creatinine clearance from serum creatinine. Nephron 1976;16:31–41.
- Inker LA et al. CKD-EPI cystatin C equations. N Engl J Med 2012;367:20–9.
Educational reference only — not a substitute for clinical judgment, institutional protocols, or specialist advice. Calculations run in your browser; nothing you enter is sent or stored.