How to use this dog and cat CKD calculator
- Select dog or cat, because the IRIS thresholds differ by species.
- Enter the latest stable blood creatinine result and choose mg/dL or µmol/L.
- Add SDMA if available. Using both kidney markers gives more context than either value alone.
- Add UPC and systolic blood pressure to calculate the two recommended IRIS substages.
- Review the estimate with the veterinarian managing the patient. The number should never be interpreted without the history, hydration, urinalysis, examination and trends over time.
What the four IRIS CKD stages mean
IRIS stages help veterinarians describe the loss of kidney function, plan monitoring and tailor treatment after chronic kidney disease has been confirmed. A higher stage generally reflects lower kidney filtration, but the result is not a stand-alone prognosis.
| Stage | Dog creatinine | Cat creatinine | Dog SDMA | Cat SDMA |
|---|---|---|---|---|
| 1 | <1.4 mg/dL <125 µmol/L | <1.6 mg/dL <140 µmol/L | <18 µg/dL | <18 µg/dL |
| 2 | 1.4–2.8 mg/dL 125–250 µmol/L | 1.6–2.8 mg/dL 140–250 µmol/L | 18–35 µg/dL | 18–25 µg/dL |
| 3 | >2.8–5.0 mg/dL 251–440 µmol/L | >2.8–5.0 mg/dL 251–440 µmol/L | 36–54 µg/dL | 26–38 µg/dL |
| 4 | >5.0 mg/dL >440 µmol/L | >5.0 mg/dL >440 µmol/L | >54 µg/dL | >38 µg/dL |
Stage 1 requires other evidence of kidney disease; values in the Stage 1 range do not diagnose CKD on their own.
IRIS Stage 1
Creatinine may remain within the reference interval. Another persistent kidney abnormality, such as raised SDMA, renal proteinuria, poor urine concentration or abnormal imaging, is needed to support CKD.
IRIS Stage 2
Mild reduction in kidney function. Many dogs and cats have few or no obvious signs, so renal diet, hydration, phosphorus, UPC and blood-pressure planning become important.
IRIS Stage 3
Moderate kidney dysfunction. Increased thirst and urination, reduced appetite, nausea, weight loss, dehydration or anaemia may become more apparent and require active management.
IRIS Stage 4
Advanced kidney dysfunction with a higher risk of uraemic illness. Poor appetite, vomiting, weakness or dehydration needs prompt veterinary attention and close quality-of-life support.
Creatinine vs SDMA in kidney staging
Creatinine is a widely available marker of kidney filtration, but hydration, recent meat intake and muscle mass can affect the result. IRIS recommends a fasting sample and stable measurements from an adequately hydrated patient.
SDMA may identify reduced filtration earlier than creatinine and is less affected by muscle mass. It is still not a diagnosis by itself. Results should be persistent and interpreted alongside the species, breed, age, concurrent disease, urine findings and kidney imaging where indicated.
When creatinine and SDMA point to different stages, the calculator displays a conservative provisional estimate. A veterinarian should review possible reasons for the discrepancy and repeat stable results in approximately two to four weeks before the stage is finalised.
Why UPC and blood pressure matter
Every confirmed CKD stage should be further assessed for proteinuria and systemic hypertension. These problems may occur independently of the creatinine stage, contribute to ongoing renal injury and change the treatment plan.
- UPC substage: classifies a dog or cat as non-proteinuric, borderline proteinuric or proteinuric after pre-renal and post-renal causes of protein are excluded.
- Blood-pressure substage: estimates the risk of damage to organs such as the eyes, brain, kidneys and heart. A single stressed reading may need confirmation unless target-organ damage or severe hypertension is present.
| Species | Non-proteinuric | Borderline proteinuric | Proteinuric |
|---|---|---|---|
| Dog | UPC <0.2 | UPC 0.2–0.5 | UPC >0.5 |
| Cat | UPC <0.2 | UPC 0.2–0.4 | UPC >0.4 |
Renal proteinuria should be distinguished from pre-renal and post-renal proteinuria. IRIS ideally confirms persistence using at least three urine samples collected over two or more weeks.
| Systolic pressure | IRIS substage | Target-organ-damage risk |
|---|---|---|
| <140 mmHg | Normotensive | Minimal |
| 140–159 mmHg | Prehypertensive | Low |
| 160–179 mmHg | Hypertensive | Moderate |
| ≥180 mmHg | Severely hypertensive | High |
When not to use IRIS CKD staging
Do not use this calculator for a dehydrated or haemodynamically unstable patient, urinary obstruction, rapidly changing kidney values, suspected toxin exposure, acute kidney injury or acute-on-chronic decompensation. Those situations require direct veterinary assessment and may use the separate IRIS acute kidney injury grading system.
What to discuss with your veterinarian
- Whether the history and repeat results confirm stable chronic kidney disease rather than pre-renal, acute or post-renal disease.
- Creatinine and SDMA trends, body weight, muscle condition and hydration.
- Urinalysis, urine specific gravity, urine culture where indicated and confirmation of persistent renal proteinuria.
- Standardised systolic blood-pressure measurements and any evidence of target-organ damage.
- Phosphorus, potassium, bicarbonate, haematocrit and other complications that do not assign the stage but may change management.
- An individual monitoring, nutrition and treatment plan appropriate for the species, CKD stage, substages and concurrent disease.
Kidney disease staging FAQs
Can creatinine or SDMA alone diagnose chronic kidney disease?
No. IRIS staging starts after CKD has been diagnosed in a stable, adequately hydrated patient. Results should be persistent and interpreted with the history, examination, urinalysis and diagnostic imaging where appropriate.
Can a dog or cat have Stage 1 CKD with normal creatinine?
Yes, but normal creatinine alone does not mean Stage 1 CKD. Another persistent renal abnormality must establish the diagnosis, such as a persistent SDMA increase above 14 µg/dL, renal proteinuria, inappropriate urine concentration, an increasing kidney-marker trend or abnormal kidney imaging.
What if creatinine and SDMA indicate different IRIS stages?
Factors such as muscle mass, age, breed and concurrent disease can create a discrepancy. IRIS advises repeating stable values in approximately two to four weeks. If the difference persists, using the higher stage is a conservative approach while the veterinarian interprets the complete clinical picture.
Can dehydration make the CKD stage look worse?
Yes. Dehydration and reduced circulation can increase kidney markers without representing a stable CKD stage. Staging should use results from an adequately hydrated, clinically stable patient after pre-renal and post-renal causes have been excluded.
Can this calculator be used for acute kidney injury?
No. This is an IRIS CKD staging calculator for stable chronic disease. Acute kidney injury has a separate IRIS grading system and can require urgent treatment.
What do UPC and blood-pressure substages mean?
UPC classifies renal protein loss, while systolic blood pressure estimates the risk of target-organ damage. Both affect monitoring and may create a specific treatment target at any CKD stage.
Does one high blood-pressure reading confirm hypertension?
Not always. Stress, technique, cuff selection and patient movement can alter a reading, so standardised repeat measurements are usually important. Evidence of acute target-organ damage may require immediate treatment without waiting to demonstrate persistence.
Are BUN and phosphorus used to assign the IRIS stage?
No. IRIS Stage 1–4 is assigned from stable creatinine and/or SDMA. BUN, phosphorus, potassium, bicarbonate, haematocrit, urinalysis and other findings help assess the whole patient and guide management.
Should kidney values be repeated before assigning an IRIS stage?
Yes. Stable kidney function should be documented. Creatinine and SDMA are ideally measured on at least two occasions in a fasted, adequately hydrated patient, with the interval guided by the clinical situation.
Does an IRIS stage predict how long a dog or cat will live?
No single stage can predict an individual pet's survival. Trends over time, complications, concurrent disease, appetite, body condition and response to treatment all matter.