Chronic Kidney Disease: What the IRIS Stage Means
Your vet said stage 2 or stage 3. What the IRIS stages measure, what the extra labels for protein and blood pressure mean, and what treatment aims to do.
Written by thecanineledger
When a vet diagnoses chronic kidney disease (CKD) in a dog, they usually give it a stage from 1 to 4. The stages come from the International Renal Interest Society (IRIS), an independent group of veterinary kidney specialists, and they are used by vets around the world.
A stage is not a countdown. IRIS describes staging as a way “to facilitate appropriate treatment and monitoring of the canine or feline patient” (IRIS Staging of CKD, modified 2026). While the stage does say something about how far the disease has gone, it mostly tells your vet which treatments make sense now.
1. How common it is, and how it shows
In a study of more than 107,000 dogs at UK practices, kidney disease was diagnosed in 0.21% of dogs, with increasing age and certain breeds, including Cocker Spaniels and Cavalier King Charles Spaniels, as risk factors (O’Neill et al., J Vet Intern Med 2013).
The signs vets recorded included “halitosis, weight loss, polyuria/polydipsia, urinary incontinence, vomiting, decreased appetite, lethargy, and diarrhea.” Polyuria and polydipsia mean passing more urine and drinking more. Early on, many dogs show no signs at all.
2. What the stage is based on
The stage is based on two blood tests that reflect how well the kidneys filter: creatinine and SDMA. IRIS says staging uses “fasting blood creatinine or fasting blood SDMA concentration or (preferably) both assessed on at least two occasions in a hydrated, stable patient.”
That last part matters. A dog who is dehydrated or acutely ill can have high results that settle with treatment. One test isn’t enough to stage.
The IRIS 2026 cut-offs for dogs:
| Stage | Creatinine (mg/dl) | Creatinine (µmol/l) | SDMA (µg/dl) |
|---|---|---|---|
| 1 | under 1.4 | under 125 | under 18 |
| 2 | 1.4 to 2.8 | 125 to 250 | 18 to 35 |
| 3 | 2.9 to 5.0 | 251 to 440 | 36 to 54 |
| 4 | over 5.0 | over 440 | over 54 |
IRIS notes that the creatinine figures “apply to average size dogs”, and that greyhounds naturally run higher. Your lab report may use either unit.
Our note: Don’t stage your dog from a single result. Staging needs results from at least two occasions.
3. What each stage means
In IRIS’s descriptions:
- Stage 1: blood creatinine is normal, but there is another sign of kidney disease, such as protein in the urine or abnormal kidneys on a scan.
- Stage 2: “Clinical signs usually mild or absent.”
- Stage 3: “Moderate renal azotemia. Many extrarenal signs may be present, but their extent and severity may vary.” Azotaemia means waste products building up in the blood; extrarenal signs are signs outside the kidneys, such as poor appetite or vomiting.
- Stage 4: “Increasing risk of systemic clinical signs and uremic crises.” A uraemic crisis is a sudden worsening when waste products build up.
4. The two extra labels: protein and blood pressure
Your vet may add two more labels after the stage.
Proteinuria means protein leaking into the urine. IRIS says the urine protein-to-creatinine ratio (UP/C) “should be measured in all dogs and cats with CKD”, ideally on at least two samples. The labels are non-proteinuric, borderline or proteinuric.
Blood pressure. High blood pressure can cause further harm, which IRIS calls target organ damage. IRIS labels dogs from normotensive to severely hypertensive, based on several readings, “preferably done during repeated patient visits to the clinic on separate days.”
These labels matter because both can be treated, and treating them is part of slowing the disease.
5. What treatment aims to do
IRIS’s treatment recommendations for dogs divide treatment into two aims: “Those that slow progression of CKD and thereby preserve remaining kidney function for longer” and “Those that seek to improve the quality of life of the dog, reducing signs of CKD” (IRIS Treatment Recommendations for CKD in Dogs, 2026).
In early stages the focus is on slowing the disease. IRIS says that “By Stage 4, treatments that are directed towards mollifying clinical signs and improve quality of life assume greater importance”.
Some things IRIS recommends at every stage are simple:
- Water. Dogs with CKD should “have fresh water available at all times for drinking.”
- Medicines that can harm the kidneys should be stopped where possible. Tell your vet about everything your dog takes, including painkillers. → Ibuprofen, Paracetamol and Other Human Painkillers
Diet. From stage 2, IRIS advises vets to “Consider feeding a clinical renal diet: this may be accomplished more easily early in the course of CKD, before inappetence develops.” An older randomised trial in 38 dogs found that a renal diet “had a beneficial effect regarding uremic crises and mortality rate in dogs with mild and moderate renal failure” (Jacob et al., J Am Vet Med Assoc 2002). A home-made kidney diet needs to be formulated by a veterinary nutritionist. → Homemade Dog Food, Done Right: What the Evidence Actually Says
We don’t give medicine names or doses. IRIS itself notes that “Some of the treatment recommendations are not authorized for use in all geographical regions”. Your vet will choose.
Our note: We based “from stage 2” on where that line appears in the IRIS recommendations. Ask your vet whether a renal diet suits your dog, especially if it has protein in its urine.
Our note: Jacob 2002 is small (38 dogs), and its sample size is reported inconsistently elsewhere. We didn’t find anything newer.
6. How long dogs live with CKD
This is the question most owners ask, and the honest answer is that it varies widely. In the UK practice study, the median survival from diagnosis was 226 days, and the IRIS stage at diagnosis was linked to survival (O’Neill et al. 2013). A median means half lived longer, and half less. Dogs diagnosed early, and dogs whose blood pressure and protein loss are controlled, may do much better.
Our note: The 226-day median comes from UK general practices in 2010–11 and mixes all stages. It isn’t a forecast for a dog at stage 1 or 2.
For owners of a dog at stage 4: → Saying Goodbye: An Evidence-Based Guide to Your Dog’s Final Chapter
7. What we could not verify
| Commonly said | What we found |
|---|---|
| “Stage 3 means months to live” | Too simple. Stage is linked to survival, but treatment and other labels matter. |
| “Low-protein diets are needed from diagnosis” | IRIS says consider a renal diet, placed under stage 2 in its dog recommendations. |
| “One high creatinine means kidney disease” | No. IRIS stages on at least two tests in a hydrated, stable dog. |
| “SDMA results are the same at every lab” | Not yet. IRIS says the methodology “has not yet been standardized”. |
Sources
- International Renal Interest Society: IRIS Staging of CKD (modified 2026) (expert guideline, not peer-reviewed; read in full)
- International Renal Interest Society: Treatment Recommendations for CKD in Dogs (2026) (expert guideline; read)
- O’Neill DG, Elliott J, Church DB, McGreevy PD, Thomson PC, Brodbelt DC. Chronic kidney disease in dogs in UK veterinary practices: prevalence, risk factors, and survival (J Vet Intern Med 2013; abstract read)
- Jacob F, Polzin DJ, Osborne CA, et al. Clinical evaluation of dietary modification for treatment of spontaneous chronic renal failure in dogs (J Am Vet Med Assoc 2002; randomised controlled trial, 38 dogs; abstract read)
Always confirm with your vet before acting on anything on this page.