🐈Cat Health🩺Chronic & Systemic

Cat Chronic Kidney Disease Stages: IRIS Staging Explained

5 min readUpdated Nov 3, 2026

General guidance — not a diagnosis. When in doubt, call your vet.

What Do Cat Chronic Kidney Disease Stages Mean?

Cat chronic kidney disease (CKD) has four IRIS stages. The stage describes the degree of kidney dysfunction and helps your vet plan care. It is not a countdown or a treatment prescription on its own.

CKD must be diagnosed before staging. IRIS uses fasting creatinine and/or SDMA, preferably both, measured on at least two occasions in a hydrated, stable patient. A single abnormal result during dehydration or acute illness is not enough to assign a reliable chronic stage.[1]

Ask your vet to explain which findings establish CKD, whether the results are stable, and what needs checking next. Keep copies of laboratory results so changes can be discussed together.

The Four IRIS Stages in Cats

These are the current feline blood-marker ranges. Read them with your vet; normal creatinine does not exclude early disease.[1]

Stage	Creatinine (mg/dl)	SDMA (μg/dl)
1	<1.6	<18
2	1.6–2.8	18–25
3	2.9–5.0	26–38
4	>5.0	>38

Stage 1 requires other evidence of kidney disease. Early stages may have few or no visible signs; later stages carry greater risk of systemic illness. Persistently higher SDMA can justify staging and treating above the creatinine-based stage.[1]

Care is individualized. In early disease, your vet investigates treatable contributors and complications. From stage 2, a clinical renal diet is considered; phosphorus management depends on testing and response. Later-stage care increasingly addresses nausea, appetite, hydration, anemia, and comfort. Nutritional support, including a feeding tube, may be discussed when needed.[2]

A controlled trial in cats with stage 2 or 3 CKD found fewer uremic episodes and renal-related deaths with the renal diet tested than with a maintenance diet.[3]

Ask which problem each treatment addresses and what improvement you should watch for. If your cat rejects food or cannot tolerate medication, contact the team so the plan can be adjusted.

Why Urine Protein and Blood Pressure Matter

Urine protein and blood pressure are substages, separate from the main blood-marker stage. Persistent renal protein loss and hypertension can require treatment even in early CKD. Your vet needs to establish persistence and interpret results in context; a single reading does not automatically mean medication is necessary. Evidence of hypertension-related organ damage changes the urgency.[2]

Ask for the main stage and both substages to be written down. Also ask whether your cat has complications that need attention before the next routine check.

Caring for Your Cat Between Visits

Home fluids are not automatic for a particular stage. AAHA notes that the ideal frequency has not been directly studied. The amount, fluid type, and schedule must come from your vet, especially if heart disease is present.[4]

Watch for a change in breathing during fluid treatment. Fluid overload can cause increased breathing effort or rate; this needs urgent veterinary assessment.[5]

Keep a simple daily record of meals, vomiting, drinking, urination, and comfortable activities. Bring questions and examples to rechecks. If weight loss is the main change you notice, see cat weight loss warning signs; hyperthyroidism in cats explains another condition your vet may investigate.

When to See a Vet

Go to an emergency vet now for labored or open-mouth breathing, particularly during or after fluids.
Seek emergency care now for collapse, seizures, sudden blindness, or repeated straining with little or no urine.
Contact your vet today if your cat stops eating, vomits repeatedly, or becomes markedly weaker or less responsive.
Book a prompt examination for increasing thirst or urination, unexplained weight loss, or a sustained drop in appetite; do not wait for severe illness.

For cat owners

Check your cat’s symptoms

Reading about a symptom? Describe what is happening to your pet to begin an assessment.

Frequently Asked Questions

Can stage 1 or 2 kidney disease be reversed?

CKD management aims to preserve remaining function and keep your cat comfortable; it does not promise a cure. Ask whether the diagnosis is confirmed and whether another treatable problem is contributing. A sudden deterioration also needs reassessment rather than an assumption that chronic disease has simply advanced.

How long can a cat live with stage 3 kidney disease?

A stage is useful for planning care, but it cannot give your cat an individual survival date. Ask your vet to discuss the trend in results alongside appetite, body weight, hydration, complications, and response to treatment. Revisit the plan when comfortable routines become harder to maintain.

Does every cat with CKD need a prescription renal diet?

Discuss a veterinary renal diet, particularly from stage 2 onward. A controlled trial in cats with stage 2 or 3 CKD found fewer uremic episodes and renal-related deaths with the renal diet tested, compared with a maintenance diet. That does not establish a benefit for every diet or predict an individual lifespan.[3]

Are subcutaneous fluids at home safe?

They can be appropriate when prescribed for your cat and taught by your veterinary team. Ask for written instructions, monitoring advice, and clear reasons to pause and call. AAHA cautions that underlying heart or kidney disease increases concern about fluid overload; giving fluids under the skin does not remove that risk.[4]

How often should my cat have kidney rechecks?

The schedule should reflect stability, symptoms, treatment changes, and your cat’s tolerance of visits. The current feline consensus recommends individualizing monitoring. Keep a record of appetite, weight, drinking, litter-box changes, and treatment difficulties to share with the team; deterioration should prompt contact before the planned appointment.[6]

What should I ask about treatment costs?

Request an itemized estimate for diagnosis, initial treatment, and follow-up rather than relying on a universal monthly figure. Ask which tests will change the immediate plan, which supplies are recurring, and how the clinic can prioritize care within your budget. Tell the team if giving medication or fluids at home is becoming difficult.