Understand the four dog kidney disease stages, IRIS test values, symptoms and substages, plus what to discuss with your veterinarian about monitoring and care.
The International Renal Interest Society (IRIS) classifies chronic kidney disease in dogs into four stages based on stable-state blood markers (creatinine and SDMA). Each stage carries different symptoms, treatment goals and monitoring needs. Staging requires a confirmed CKD diagnosis in a hydrated, stable patient — a single blood test during illness does not assign a stage. Work with your veterinarian to understand what your dog's stage means for care, not to predict a fixed outcome.
For related guidance, see kidney disease blood tests for dogs.
Staging should only be done after CKD has been confirmed and the dog is adequately hydrated and in a stable clinical state. Values drawn from a dehydrated, vomiting or acutely ill dog may be artificially high and do not accurately reflect chronic kidney function. If your dog is ill at the time of the blood draw, your vet may recheck once the dog is stabilized before assigning a stage.
It is also important to know that the IRIS CKD staging system is not the same as acute kidney injury (AKI) grading. AKI is a sudden decline that may be reversible; CKD is a chronic, typically progressive condition. These two classifications should not be used interchangeably.
Creatinine is a waste product filtered by the kidneys. As kidney function declines, creatinine accumulates in the blood. IRIS uses specific creatinine ranges for each stage.
SDMA (symmetric dimethylarginine) is a newer biomarker that can detect kidney function loss earlier than creatinine — sometimes when only about 25–40% of function is gone. IRIS guidelines now include SDMA alongside creatinine for staging.
A dog may have CKD confirmed by other evidence even when creatinine is still normal. That evidence can include persistently dilute urine, structural changes on imaging, persistent proteinuria or an abnormal kidney biopsy.
Canine creatinine: < 1.4 mg/dL (< 125 μmol/L) SDMA: < 18 μg/dL
At Stage 1, creatinine and SDMA remain within or just at the top of normal ranges, yet there is already evidence of kidney disease — such as consistently dilute urine, kidney abnormalities on ultrasound or persistent proteinuria. Most dogs at this stage show no obvious outward signs. Some may drink and urinate slightly more than usual, but many owners notice nothing at all.
Because symptoms are absent or minimal, Stage 1 CKD is most often caught during routine senior wellness blood work. Early detection matters: management strategies started here — dietary adjustments, hydration support and treatment of contributing conditions — may help slow progression.
Canine creatinine: 1.4–2.8 mg/dL (125–250 μmol/L) SDMA: 18–35 μg/dL
Blood creatinine is now mildly elevated. Dogs at Stage 2 may begin showing subtle clinical signs:
These signs can be easy to overlook or attribute to normal aging. Stage 2 is often described as an important intervention window — proactive management, including a veterinarian-guided renal diet and monitoring for proteinuria and blood pressure, can help support remaining kidney function. However, the term "golden window" overstates what is guaranteed: the benefit of early intervention is real but varies by individual.
Canine creatinine: 2.9–5.0 mg/dL (251–440 μmol/L) SDMA: 36–54 μg/dL
At Stage 3, azotemia (waste buildup in the blood) becomes more pronounced and clinical signs are typically noticeable:
Management intensifies. Depending on the individual dog's lab work and clinical picture, the veterinarian may recommend a renal-specific diet, phosphorus binders, anti-nausea medication, subcutaneous fluids at home, antihypertensives or erythropoiesis-stimulating agents. The specific combination is tailored to the dog — there is no single standard Stage 3 treatment list.
Canine creatinine: > 5.0 mg/dL (> 440 μmol/L) SDMA: > 54 μg/dL
Stage 4 represents advanced CKD. Many dogs at this stage develop signs of uremic syndrome:
Some dogs may also develop neurological signs such as tremors or, less commonly, seizures.
Not every Stage 4 dog shows every symptom listed above — the clinical picture varies. The focus of care shifts toward maintaining comfort and quality of life, with close veterinary guidance.
When a dog's kidney disease reaches the point where medical management can no longer keep the animal comfortable, end-of-life discussions become part of the care plan. Signs that quality of life is declining may include uncontrollable nausea, refusal to eat or drink, severe weakness and progressive weight loss despite treatment.
Your veterinarian can help you assess your dog's comfort using quality-of-life tools and guide decisions about hospice care or humane euthanasia. These conversations are never easy, but they are an essential part of responsible care.
IRIS staging does not stop at the creatinine/SDMA-based stage number. Two additional substages refine the picture and change management:
Proteinuria substaging (based on urine protein-to-creatinine ratio, UPC):
| Classification | Dog UPC |
|---|---|
| Non-proteinuric | < 0.2 |
| Borderline proteinuric | 0.2–0.5 |
| Proteinuric | > 0.5 |
Proteinuria indicates ongoing kidney damage and is an independent risk factor for progression. Dogs classified as proteinuric typically benefit from treatment to reduce protein loss.
Blood pressure substaging:
| Risk category | Systolic blood pressure |
|---|---|
| Normotensive | < 140 mmHg |
| Prehypertensive | 140–159 mmHg |
| Hypertensive | 160–179 mmHg |
| Severely hypertensive | ≥ 180 mmHg |
High blood pressure accelerates kidney damage and can injure the eyes, brain and heart. Antihypertensive medication may be recommended depending on the substage and the presence of target-organ damage.
Both substages should be reassessed at each recheck visit because they can change independently of the creatinine-based stage.
This happens. SDMA can detect kidney function loss earlier than creatinine, and the two markers sometimes place a dog in different stages. When they disagree, the IRIS guidelines recommend considering the higher stage for management decisions and discussing the discrepancy with your veterinarian.
Owners understandably want to know how long a dog at a given stage will live. The honest answer is that stage alone does not determine life expectancy. Factors that influence outcome include:
A Stage 2 dog with severe proteinuria and uncontrolled hypertension may decline faster than a Stage 3 dog with stable values and good dietary compliance. Use the stage as a framework for discussion, not as a countdown.
Regular rechecks allow your veterinarian to detect changes early and adjust treatment before the dog feels worse. Monitoring frequency depends on the stage and clinical stability:
Your veterinarian will determine the right schedule based on your dog's trend, not just the stage label.
A typical recheck visit includes:
Tracking these values over time reveals whether the disease is stable, slowly progressing or rapidly worsening — information that is far more useful than a single snapshot.
Disclaimer: This article is for educational purposes only and does not replace professional veterinary advice or diagnosis. If your dog has been diagnosed with kidney disease, work with your veterinarian to develop an individualized care plan.