CKD stages (IRIS) explained for owners
This guide is general information and not a substitute for your veterinarian. Your pet's stage and treatment are set by your vet from their own tests.
When your vet mentions your pet's kidney disease is "stage 2" or "stage 3," it helps to know what that means and, just as importantly, what it doesn't. The short version: IRIS staging is a system vets use to describe how far chronic kidney disease has progressed, from the earliest stage to the most advanced, so they can tailor treatment and monitoring. It is not a countdown or a life expectancy.
Below is what the staging is based on, what each stage tends to change about daily care, why it isn't a timer, and what to ask and track after a staging result. IRIS stands for the International Renal Interest Society, the group whose system most vets use.
What IRIS staging is based on
Your vet sets the stage mainly from two blood values: creatinine and SDMA, both markers of how well the kidneys are filtering. A key detail is that staging is done when your pet is stable and well-hydrated, and usually confirmed on more than one occasion, because a single reading taken when a pet is dehydrated or unwell can look worse than the real, settled picture.
On top of the stage, your vet adds two sub-stages that shape treatment:
- Urine protein, often measured as a UPC ratio, showing how much protein is leaking into the urine.
- Blood pressure, since high blood pressure is common in CKD and can speed up damage.
So a full staging isn't just one number. It's the stage plus the protein and blood pressure picture, which is why your vet may run several tests before settling on it. The specific value ranges behind each stage are your vet's to apply, and they differ between dogs and cats.
Stage by stage: what changes for daily care
The stages run from 1 to 4, roughly earliest to most advanced. Every pet is different, and your vet's plan for your pet always wins over any general description, but broadly:
- Stage 1 is the earliest, often with no outward signs, picked up on blood or urine tests before you'd notice anything. Care is usually about a baseline, monitoring, and catching anything treatable early, like protein in the urine or high blood pressure.
- Stage 2 is still mild. This is often where the first everyday signs can appear, such as drinking and urinating more. Diet, hydration, and regular rechecks typically come into focus here.
- Stage 3 is moderate, where more noticeable signs tend to show, appetite changes, weight loss, low energy, and where treatment usually broadens to manage them and keep your pet comfortable.
- Stage 4 is the most advanced, with the most significant signs, and the most hands-on care, often including things like subcutaneous fluids at home alongside close support for appetite and comfort.
Across every stage, the daily levers are similar, the right diet, good hydration, and steady monitoring. What shifts is the intensity and how much active support your pet needs.
Why staging isn't a countdown
This is the part worth holding onto. A stage describes your pet's kidney function right now. It is not a forecast of how long they have. Many pets sit at an early stage for a long time, some for years, especially when the disease is caught early and managed well.
A stage can also stay put. The point of staging isn't to watch a number climb, it's to match the care to where things are and to notice change early enough to act. And because staging is done when your pet is stable, a scary value during an illness or a dehydrated spell often isn't the true stage, it can settle once your pet is treated. Ask your vet what your pet's stable baseline is, rather than reading a one-off result as fate.
Questions to ask after a staging result
A staging appointment is a good moment to leave with a clear plan. Worth asking:
- What stage is my pet, and was it measured when they were stable and well-hydrated?
- What do the protein and blood pressure results add to that?
- What changes now, in diet, fluids, or medication?
- What should I watch for at home that would mean calling sooner?
- When is the next recheck, and what will it compare against?
Writing the answers down turns a dense appointment into something you can act on all week. It also gives the next visit a reference point.
Tracking between rechecks
Staging happens a few times a year at most. What fills the gap is what you notice at home, and it's what makes each recheck meaningful. Keep a light, steady record of:
- Weight, weekly if you can, since slow loss is easy to miss without numbers.
- Appetite, how keen your pet is and how much they finish.
- Thirst and urination, the direction and any sudden change.
- Energy and mood, the everyday sense of how your pet is doing.
- Medications and fluids given, so the plan and the results line up.
This is the same tracking the CKD monitoring guide sets out, and it's what lets you and your vet see whether your pet is holding steady at their stage or drifting, long before a single test would show it. With a slow condition, the trend is the whole story.
Common questions
My pet jumped a stage after being ill. Is it permanent?
Not necessarily. A value measured during an illness or when your pet is dehydrated can read worse than their stable state. Vets usually recheck once your pet is well again to find the true stage. Ask about a repeat test before treating a crisis reading as the new normal.
Is a higher stage always worse?
A higher stage means more advanced disease and usually more hands-on care, but it isn't a verdict. Plenty of pets live comfortably with support at a later stage. What matters most is how your pet is doing day to day and whether things are stable, which is exactly what your tracking shows.
How often should my pet be re-staged?
That's your vet's call, and it depends on the stage and how stable your pet is, more often early or after a change, less often when steady. If you're not sure when the next one is due, ask, and note it so it doesn't slip.
Felova does exactly this, a calm place to track weight, appetite, and thirst so the trend between rechecks is there when your vet needs it. It's on Android now.
Get it on Android →