IRIS Stage 3 · Moderate
IRIS Stage 3 kidney disease in cats: what it means
Kidney values are moderately raised and cats may start to show signs such as reduced appetite, weight loss, nausea or dehydration. Supportive care — fluids, anti-nausea medicine, phosphorus control — often becomes part of daily life.
Please read first
These are reference ranges, not a stage. Only your vet can stage CKD — in a cat that is clinically stable and well hydrated, using results from at least two occasions and the whole clinical picture. The values below describe the range IRIS associates with Stage 3. A single test result in this range does not mean a cat “is” Stage 3.
The values IRIS associates with Stage 3
| Blood creatinine | 2.9 – 5.0 mg/dL (251 – 440 µmol/L) |
|---|---|
| SDMA | 26 – 38 µg/dL |
| Phosphorus target | 2.5 – 5 mg/dL |
Source: IRIS Staging of CKD (modified 2023) — iris-kidney.com; phosphate targets: 2026 iCatCare consensus guidelines.
What care often looks like
Every cat is different, and your vet will tailor care to yours. At this stage, care often includes:
- Supporting appetite and treating nausea, which is common and very treatable. Many cats feel noticeably better with anti-nausea medicine your vet prescribes.
- Helping hydration, which may include subcutaneous fluids at home if your vet recommends them.
- Keeping phosphorus within the IRIS target with diet and binders, and checking potassium, which is often low.
- Watching for anemia, constipation, dental pain and high blood pressure, all of which are common and can be managed.
How long do cats live at Stage 3?
There is no single number that predicts how long an individual cat will live with values in the Stage 3 range. Some cats stay stable for a long time, especially when appetite, hydration and phosphorus are well managed. Ask your vet what they expect for your cat, and what would change their view.
Substaging: urine protein and blood pressure
IRIS also “substages” every cat with CKD by protein in the urine (UPC) and by blood pressure, because both affect care. These apply at any stage.
| UPC | Substage |
|---|---|
| < 0.2 | Non-proteinuric |
| 0.2 – 0.4 | Borderline proteinuric |
| > 0.4 | Proteinuric |
| Systolic (mmHg) | Substage |
|---|---|
| < 140 | Normotensive |
| 140 – 159 | Prehypertensive |
| 160 – 179 | Hypertensive |
| ≥ 180 | Severely hypertensive |
Questions to ask your vet
Ask your vet
- What can we do to support my cat’s appetite and comfort?
- Would subcutaneous fluids help, and can someone show me how?
- Are potassium, phosphorus and red blood cells where you want them?
- What signs should make me call you right away?
Not sure where the numbers sit?
Type your cat’s creatinine and SDMA into the free Lab Decoder to see them on the IRIS reference bars.
Frequently asked questions
What does IRIS Stage 3 mean for a cat?
Kidney values are moderately raised and cats may start to show signs such as reduced appetite, weight loss, nausea or dehydration. Supportive care — fluids, anti-nausea medicine, phosphorus control — often becomes part of daily life. Only your vet can stage your cat, using repeated tests on a stable, well-hydrated cat.
What creatinine level is IRIS Stage 3 in cats?
IRIS associates a blood creatinine of 2.9 – 5.0 mg/dL (251 – 440 µmol/L) with Stage 3 in cats, alongside an SDMA of 26 – 38 µg/dL.
What is the life expectancy for a cat with Stage 3 kidney disease?
There is no single number that predicts how long an individual cat will live with values in the Stage 3 range. Some cats stay stable for a long time, especially when appetite, hydration and phosphorus are well managed. Ask your vet what they expect for your cat, and what would change their view.
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