AKIN Classification for Acute Kidney Injury (AKI) online calculator

NB! Patients on renal replacement therapy (RRT) are considered to be stage 3 regardless of whether they meet formal criteria!

AKI severity

Serum creatinine

Normal creatinine, or < 1.5x from baseline
Absolute increase ≥ 0.3 mg/dL (≥ 26.4 μmol/L), or ≥ 1.5-2x from baseline
Increase to >2-3x from baseline
Increase to > 3x from baseline, or ≥ 4.0 mg/dL (≥ 354 μmol/L) with acute increase ≥ 0.5 mg/dL (≥ 44 μmol/L)

Urine output:
≥ 0.5 mL/kg per hour for > 6 hours
< 0.5 mL/kg per hour for > 6 hours
< 0.5 mL/kg per hour for > 12 hours
< 0.3 mL/kg per hour for ≥ 24 hours, or anuria for 12 hours

Patient	AKI severity
0	0

To be diagnosed with acute kidney injury by the AKIN definition, patient must have at least one of the following within the past 48 hours:

Absolute increase in serum creatinine ≥0.3 mg/dL (≥26.4 μmol/L).
Increase in serum creatinine ≥1.5x above baseline.
Oliguria (urine output <0.5 mL/kg per hour) for >6 hours.

Criteria for AKI (must have ≥1 within the past 48 hrs)

Absolute increase in serum creatinine ≥0.3 mg/dL (≥26.4 μmol/L)	No	Yes
Increase in serum creatinine ≥1.5x above baseline	No	Yes
Oliguria (urine output <0.5 mL/kg per hour) for >6 hours	No	Yes

Note: Patients on renal replacement therapy (RRT) are considered to be stage 3 regardless of whether they meet formal criteria.

Then, select the appropriate criterion leading to the highest possible stage, e.g. if serum creatinine is normal but urine output is <0.5 mL/kg/hour for >12 hours, AKIN Stage is 2.

AKIN Classification	Serum creatinine	Urine output
Not AKI according to AKIN	Normal creatinine, or <1.5x from baseline	≥0.5 mL/kg per hour for >6 hours
Stage 1	Absolute increase ≥0.3 mg/dL (≥26.4 μmol/L), or ≥1.5-2x from baseline	<0.5 mL/kg per hour for >6 hours
Stage 2	Increase to >2-3x from baseline	<0.5 mL/kg per hour for >12 hours
Stage 3	Increase to >3x from baseline, or ≥4.0 mg/dL (≥354 μmol/L) with acute increase ≥0.5 mg/dL (≥44 μmol/L)	<0.3 mL/kg per hour for ≥24 hours, or anuria for 12 hours

References:

Mehta, R.L., Kellum, J.A., Shah, S.V. et al. Acute Kidney Injury Network: report of an initiative to improve outcomes in acute kidney injury. Crit Care 11, R31 (2007). https://doi.org/10.1186/cc5713
Lopes JA, Jorge S. The RIFLE and AKIN classifications for acute kidney injury: a critical and comprehensive review. Clin Kidney J. 2013 Feb;6(1):8-14. doi: 10.1093/ckj/sfs160. Epub 2012 Jan 1. PMID: 27818745; PMCID: PMC5094385.
Xiong, J., Tang, X., Hu, Z. et al. The RIFLE versus AKIN classification for incidence and mortality of acute kidney injury in critical ill patients: A meta-analysis. Sci Rep 5, 17917 (2015). https://doi.org/10.1038/srep17917

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