KDIGO AKI Staging Calculator — Acute Kidney Injury Stage 1, 2 or 3
Stage acute kidney injury with the KDIGO 2012 criteria from baseline and current serum creatinine, urine output per kg per hour and renal replacement therapy — stage 1, 2 or 3 with the criterion that drives it.
How it works
Stage 1: creatinine 1.5–1.9 × baseline (within 7 days) or rise ≥ 0.3 mg/dL (≥ 26.5 µmol/L) within 48 h; or urine output < 0.5 mL/kg/h for 6–12 h. Stage 2: 2.0–2.9 × baseline; or < 0.5 mL/kg/h for ≥ 12 h. Stage 3: ≥ 3.0 × baseline, or creatinine ≥ 4.0 mg/dL (353.6 µmol/L), or start of renal replacement therapy; or < 0.3 mL/kg/h for ≥ 24 h or anuria for ≥ 12 h. The higher stage from either criterion applies. 1 mg/dL = 88.4 µmol/L.
The KDIGO Clinical Practice Guideline for Acute Kidney Injury (2012) unified the earlier RIFLE and AKIN systems. Patients are staged by whichever criterion — creatinine or urine output — gives the higher stage. Higher stages carry a stepwise increase in mortality and the need for dialysis. In patients under 18, a fall in eGFR to below 35 mL/min/1.73 m² also defines stage 3; that criterion is not included here.
Worked example
Baseline creatinine 1.0 mg/dL rising to 2.1 mg/dL within 48 hours is a ratio of 2.10 × and a rise of 1.10 mg/dL — stage 2 by creatinine. Urine output of 0.6 mL/kg/h does not meet a urine criterion and no dialysis has started, so the KDIGO AKI stage is Stage 2.
Sources: KDIGO Clinical Practice Guideline for Acute Kidney Injury (2012)
Frequently asked questions
What baseline creatinine should I use?
The lowest value in the previous 7 days, or a stable outpatient value from the past few months. If none is known, guidelines suggest the lowest value during the admission or a back-calculated value, which can misclassify AKI.
Why is urine output measured per kg per hour?
It adjusts for body size. Weight is usually actual body weight; in obesity, some use ideal body weight, which avoids over-diagnosing oliguria.
How is KDIGO different from RIFLE and AKIN?
KDIGO combines RIFLE’s 7-day window for the 1.5× rise with AKIN’s 48-hour 0.3 mg/dL rise, and puts the start of dialysis in stage 3.
Does stage 1 AKI matter?
Yes. Even small creatinine rises are linked with longer stays and higher mortality; KDIGO recommends reviewing nephrotoxic drugs, volume status and blood pressure at every stage.
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Clinical decision tool for education and for use by trained clinicians alongside clinical judgement — not a diagnosis and not a substitute for medical assessment. Formulas and cut-offs come from the cited sources; local protocols may differ.