Chronic kidney disease in cats: symptoms, stages and care

Chronic kidney disease in cats is a progressive, irreversible decline in kidney function that mainly affects cats over 7 years old and that, when caught early, can be slowed down even though it has no cure.

If you have a cat older than seven, chances are your vet has mentioned the word “kidneys” at some point during a routine check-up. That’s no coincidence: chronic kidney disease is one of the most common conditions in older cats.

What makes this disease especially deceptive is how silent it is. The kidneys have an enormous functional reserve, which means a cat can lose a significant portion of kidney function without showing any visible symptoms at home. By the time clear signs appear — increased thirst, more urination, weight loss — the disease may have been progressing for some time already.

The good news is that this has a practical solution: it doesn’t depend on you spotting symptoms that simply don’t exist in the early stages, but on staying ahead of it with regular check-ups.

In this article we explain why cats are so prone to this condition, which signs you can actually observe at home — both early and advanced — how it’s diagnosed and staged, and what treatment options exist to help your cat maintain the best possible quality of life.

Why cats are so prone to chronic kidney disease

There’s no single cause that explains why cats develop this condition so frequently. In most cases, the specific origin is never identified: it’s thought to usually result from small lesions that accumulate in kidney tissue over the years — episodes of mild dehydration, minor infections, small inflammatory changes — which individually go unnoticed, but whose effect builds up over time.

Age is, by far, the most important risk factor. As a cat gets older, the kidneys accumulate more years of functional wear, which explains why prevalence rises so sharply from around 7-8 years of age. Some breeds also have a predisposition to specific hereditary forms of kidney disease — the best-known example being polycystic kidney disease in Persian cats and related breeds — but they represent a minority of all affected cats. In the vast majority of cases, we’re simply talking about a kidney that has accumulated more years of use.

Early warning signs you shouldn’t overlook

One of the keys to improving the prognosis of this disease is learning to tell the difference between the subtle signs of an early stage and the more obvious symptoms of an advanced one. The earlier it’s caught, the more room there is to act.

Early, subtle symptoms that are easy to miss

• Drinking more water than usual. This is probably the earliest and most important sign. Damaged kidneys lose their ability to concentrate urine, forcing the cat to drink more to compensate for the water loss.
• Urinating more, and more often. This is the flip side of the point above: if you notice the litter box filling up faster or need to change it more often, it’s worth paying attention.
• Slight weight loss, sometimes so gradual it’s only noticeable comparing photos taken months apart, or by feeling the spine and ribs.
• A slightly dull or less glossy coat, without other obvious signs of skin disease.

None of these signs alone confirms a kidney problem — they can have other causes — but any of them is reason enough to book a veterinary check-up, especially in cats over 7.

Symptoms of a more advanced stage

When the disease progresses without being caught earlier, symptoms become more obvious and often more worrying for the owner:

• Loss of appetite or gradually refusing food
• Lethargy and less interest in playing or interacting
• Vomiting, sometimes linked to meals
• Bad breath (uraemic odour)
• Dull coat, with less self-grooming
• General weakness and lower exercise tolerance

The 4 stages of feline chronic kidney disease (IRIS system)

The international veterinary community uses a classification system called IRIS (International Renal Interest Society) to establish which stage a cat with chronic kidney disease is in. This classification matters because the recommended treatment varies by stage: a cat newly diagnosed at an early stage isn’t managed the same way as one at an advanced stage.

The IRIS system is based mainly on blood creatinine and SDMA levels — once the disease has been confirmed as stable, not from a single one-off blood test — and is refined using two additional factors that help personalise the prognosis and treatment for each cat: the presence of protein in the urine (proteinuria) and blood pressure levels.

Within each stage, the vet also assesses proteinuria (how much protein is leaking into the urine, an indicator of damage to the kidney’s filters) and blood pressure (hypertension is common in cats with kidney disease and, if left uncontrolled, can cause further kidney damage as well as harm other organs, such as the eyes). These two sub-indices help personalise treatment beyond the numeric stage alone.

How it’s diagnosed

Diagnosing chronic kidney disease combines several complementary tests. None of them alone gives a complete picture: it’s the combination of results that allows the stage to be established and the right treatment plan to be designed.

Blood and urine tests

The blood test mainly measures urea and creatinine, two waste products that the kidneys normally filter out. When their levels rise, it indicates the kidneys are losing filtering capacity. The problem is that, with these two classic markers, the rise is only detectable once a considerable portion of kidney function has already been lost.

That’s why a more sensitive marker is playing an increasingly important role in diagnosis: SDMA (symmetric dimethylarginine), which can detect changes in kidney function at earlier stages than creatinine, allowing diagnosis to be anticipated in some cats.

The urine test is just as important. It assesses urine specific gravity (whether the kidneys are still able to concentrate urine) and the urine protein-to-creatinine ratio (UPC), which measures the proteinuria mentioned above. Dilute urine in a cat with elevated creatinine is one of the most characteristic patterns of the disease.

Blood pressure

Measuring blood pressure is part of the standard diagnostic protocol in cats with suspected or confirmed kidney disease. Hypertension can be both a cause and a consequence of kidney damage, and if left undetected and uncontrolled, it can accelerate disease progression and damage other organs, particularly the eyes.

Kidney ultrasound

Ultrasound allows the internal structure of the kidneys to be visualised: their size, shape, the differentiation between cortex and medulla, and the presence of cysts, stones or masses. It’s especially useful for distinguishing chronic kidney disease from other causes of altered kidney function, and for tracking how the kidney’s structure evolves over time.

If you’d like to understand this test better and how it’s carried out in practice, we cover it in detail in our article on ultrasound and X-ray in veterinary practice: when and why. At Rovira Veterinary Clinic we offer this diagnostic imaging test on-site, allowing the kidney work-up to be completed in the same visit.

Treatment and management: what can be done

Chronic kidney disease has no cure: damaged kidney tissue doesn’t regenerate. But that doesn’t mean there’s nothing to be done. The goal of treatment is to slow progression, manage associated symptoms, and maintain the best possible quality of life for as long as possible. The specific plan depends on the stage, the imbalances detected on testing, and how each individual cat responds, so it should always be tailored by the vet on a case-by-case basis.

Renal diet

Switching to a diet specifically formulated for kidney disease, with reduced phosphorus and high-quality, reduced protein levels, is usually the first and most important therapeutic step. Reducing the phosphorus and nitrogenous waste load that a damaged kidney has to process helps slow disease progression and reduce symptoms linked to the build-up of uraemic toxins. When blood phosphorus levels remain elevated despite the diet, the vet may add phosphate binders, substances given with food that reduce its intestinal absorption.

This is also one of the reasons why nutrition plays such an important role in managing this condition: it’s not a complement to treatment, it’s a central part of it. If you’d like to understand how that balance between protein and phosphorus is fine-tuned, and why you shouldn’t choose a therapeutic diet without supervision, we cover it in detail in our guide on feeding dogs and cats with chronic illness.

Managing blood pressure and other imbalances

When hypertension is detected, specific treatment is started to control it and protect both the kidneys and other organs sensitive to high blood pressure, such as the eyes. Similarly, some cats with kidney disease develop hypokalaemia (low blood potassium levels), which is corrected with specific supplements once confirmed by testing. Regular follow-up blood work is what allows these imbalances to be caught in time and the treatment plan adjusted accordingly.

Subcutaneous fluid therapy at home (advanced stages)

In more advanced stages of the disease, when a cat struggles to stay adequately hydrated on their own, the vet may recommend subcutaneous fluid therapy: administering fluids under the skin to improve hydration without the need for hospitalisation. Many owners learn to administer this at home after receiving the right training at the clinic, helping to keep these cats more comfortable and hydrated in their own environment.

Can it be prevented? Why check-ups from age 7-8 onwards matter

There’s no guaranteed way to prevent feline chronic kidney disease, precisely because in most cases there’s no single identifiable cause that can be avoided. But there is an effective strategy for minimising its impact: catching it as early as possible, ideally at stage 1, when there are still no visible symptoms and there’s more room to act.

That early detection depends almost entirely on routine check-ups from age 7-8 onwards, with regular blood and urine tests even when the cat appears perfectly healthy. It’s the only way to identify a change in kidney function before it translates into loss of appetite, weight loss or lethargy — in other words, before the cat has already felt a real impact on their day-to-day wellbeing.

If you’d like to know exactly how often these check-ups are recommended based on your cat’s age, we cover it in detail in our guide on how often your pet should visit the vet.

Specialist follow-up at Rovira

Catching a kidney abnormality at stage 1 requires interpreting blood work with clinical judgement, not just checking whether a value falls “within range”. Dr. Lídia Adell, a dedicated feline medicine specialist with IFEVET training at Rovira Veterinary Clinic, designs a personalised follow-up plan for every senior cat, combining blood work, blood pressure monitoring and kidney ultrasound whenever the case calls for it.

Frequently asked questions

Is chronic kidney disease in cats curable?

No, it’s an irreversible condition: damaged kidney tissue doesn’t regenerate. But that doesn’t mean it’s a death sentence. With early diagnosis and treatment tailored to each stage, most cats can maintain a good quality of life for quite some time. The goal of treatment isn’t to cure it, it’s to slow its progression and manage the symptoms.

How long can a cat live with chronic kidney disease?

It depends on many factors: the stage at diagnosis, the underlying cause if known, how the individual cat responds to treatment, and how consistent the veterinary follow-up is. Some cats diagnosed in early stages live for years with a good quality of life, while others diagnosed in advanced stages have a shorter window. There’s no universal figure that applies to every case — your vet is best placed to guide the prognosis for your specific cat, based on their evolution and regular check-ups.

Is it hereditary or does it just come with age?

In most cats, no specific cause is ever identified: it’s considered the cumulative result of small insults to the kidney over the years, which is why age is the main risk factor. Some breeds, such as Persians and Maine Coons, do have a higher predisposition to hereditary forms of kidney disease (polycystic kidney disease), but these represent a minority of cases. In the vast majority of older cats, we’re talking about progressive wear, not a genetic condition.

Does my indoor cat have a lower risk?

No. Chronic kidney disease isn’t linked to outdoor access or lifestyle in that sense — it’s a condition tied mainly to age. A cat that lives exclusively indoors carries exactly the same risk as one with access to a terrace or garden. Prevention comes down to regular check-ups from age 7-8 onwards, not limiting their time outside.

If your cat is over 7, or you’ve noticed them drinking or urinating more than usual, don’t wait for more symptoms to appear. At Rovira Veterinary Clinic we can assess their kidney function with a full check-up and, if needed, design a follow-up plan tailored to their case. Book an appointment and let’s take the first step together.