Understanding IRIS staging for kidney disease
11 March 2026 · 6 min read · Dr Jasmine Kay Ching Tung
IRIS staging is an international system for classifying chronic kidney disease. It exists so that treatment decisions are consistent, and so that owners get the same advice regardless of which clinic they walk into.
The stage (1 to 4) is set by creatinine, ideally supported by SDMA, measured on a well-hydrated, stable, fasted patient — never during a dehydration crisis.
Two substages refine it. Proteinuria is measured by urine protein:creatinine ratio, and blood pressure defines the risk of end-organ damage. Both are independently treatable and both affect prognosis.
Stage 1 and 2 are the ones worth catching. Interventions there — a renal-appropriate diet, phosphate control, treating proteinuria and hypertension — buy meaningful, good-quality time.
The IRIS Staging tool on this site reproduces the published cut-offs for dogs and cats. It is a reference aid; your vet interprets it alongside urine specific gravity, imaging and the individual patient.
This article is general education and cannot replace an examination of your individual animal. If your pet is unwell, contact your veterinarian.