Cat kidney stage calculator
For cats already diagnosed with chronic kidney disease. Have their latest blood test results handy.
Listed as CREA, CRE or Cre on the report. Skip BUN, the line next to it.
Where are these on the report?
| Test | Result | Unit | Reference |
|---|---|---|---|
| BUN | 38 | mg/dL | 16–36 |
| CRE | 1.8 | mg/dL | 0.8–2.4 |
| SDMA | 17 | µg/dL | 0–14 |
| ALT | 45 | U/L | 12–130 |
Leave blank if SDMA wasn't tested.
Add an earlier test (optional)
IRIS stages on two or more tests. If you have an earlier report, enter the same tests here, in the same unit as above.
Add urine protein and blood pressure (optional)
Listed as UPC or UPCR. It isn't reliable if the urine shows inflammation or blood.
Measured at the clinic: the higher of the two numbers. If they're on medication for it, use the reading on treatment.
Kidney stage
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Enter creatinine or SDMA to see the stage.
- Urine protein
- Blood pressure
Stages are based on fasting blood taken while your cat is stable and hydrated, on at least two occasions. With a single result, treat this as a guide and check with your vet.
What each stage means for care →Furwise · furwise.app
This only works out the stage. It can't tell whether a cat has kidney disease, and treatment is a conversation for your vet.
How it’s worked out
It follows the 2026 IRIS staging table. Creatinine below 1.6 mg/dL is stage 1, 1.6 to 2.8 is stage 2, 2.9 to 5.0 is stage 3, and above 5.0 is stage 4. SDMA's cut-offs are 18, 25 and 38 µg/dL.
With both numbers, creatinine sets the stage. If SDMA is above the top of that stage, the cat moves up one stage, never more. Older cats with little muscle can have low creatinine, and SDMA is less affected by muscle, so it fills that gap.
A urine protein:creatinine ratio below 0.2 is non-proteinuric, 0.2 to 0.4 is borderline, and above 0.4 is proteinuric. Systolic pressure below 140 is normal, 140 to 159 prehypertensive, 160 to 179 hypertensive, and 180 or more severely hypertensive.
Signs and care at each stage are covered in our guide to kidney disease in cats.
Before you read the report
Blood should be taken after fasting, and your cat shouldn't be dehydrated. Dehydration pushes kidney values up for a while, which makes the stage look worse.
The SDMA cut-offs are based on IDEXX's test method. Results from other methods may not line up exactly.
Healthy Birman cats naturally run higher SDMA and creatinine, and some sit above the reference range.
Related reading
Frequently asked questions
Creatinine is inside the report's reference range. Why is it stage 2?
Stage 2 starts at 1.6 mg/dL, which falls inside many labs' reference ranges. Creatinine only rises after a lot of kidney function is lost, so in a cat already diagnosed with kidney disease, a value near the top of the range counts as stage 2.
Creatinine and SDMA give different stages. Which one counts?
Creatinine leads. If SDMA stays higher, the cat moves up one stage. Thin cats with little muscle have lower creatinine, and SDMA reflects their kidney function better. If the two are far apart, ask your vet about retesting.
Does my cat need urine protein and blood pressure checked?
IRIS recommends both for every cat with kidney disease. They're linked to how fast the disease progresses, and your vet uses them to decide on treatment.