Kidney Disease in Cats: Signs, Diagnosis and Long-Term Care

At a glance

What it is	A gradual loss of the kidneys' ability to filter waste from the blood and balance the body's water
Who's at risk	Mostly middle-aged and older cats, though younger cats can be affected
Main signs	Drinking and peeing more, weight loss, poor appetite, vomiting, a scruffy coat, bad breath
Contagious?	No
Can it be prevented?	Not reliably, but regular check-ups help catch it early, when management tends to work best

What it is

Your cat's kidneys do a lot of quiet, essential work. They filter waste products out of the blood, which then leave the body in urine. They also help keep the right amount of water in the body, balance important salts and minerals, help control blood pressure and make a hormone that tells the body to produce red blood cells.

In chronic kidney disease (often shortened to CKD), the kidneys slowly lose their ability to do these jobs. The word "chronic" simply means long-lasting. The change usually happens over months or years rather than days, and the kidneys are very good at compensating, so a cat may have lost a good deal of kidney function before anything looks wrong from the outside.

The exact cause is often never found. Age-related wear is a big part of the picture, and other things such as past infections, inherited conditions in some breeds, high blood pressure, kidney stones or exposure to toxins can play a role. It's worth knowing that lilies are extremely dangerous to cats and can cause sudden kidney damage, which is a separate emergency from the slow, age-related form described here. You can read more about household dangers on our toxic foods page.

Vets sometimes also see acute kidney injury, which comes on suddenly over hours or days. That is an emergency and is different from the gradual condition this article is mainly about.

Signs to watch for

Because kidney disease develops slowly, the signs often appear gradually and can be mistaken for "just getting older". Things you might notice include:

• Drinking more. You may find yourself refilling the water bowl more often, or see your cat drinking from taps, puddles or the shower.
• Peeing more. Litter trays get heavier or need changing more often, and clumps may be larger.
• Weight loss. This can be subtle at first. You might feel your cat's spine or hips more easily when you stroke them.
• Poor or fussy appetite. Your cat may show interest in food then walk away, or eat less than usual.
• Vomiting. Occasional sickness that becomes more frequent.
• A dull or unkempt coat. Cats who feel unwell often groom less.
• Bad breath. Waste products building up in the blood can give the breath an unpleasant, sometimes ammonia-like smell, and can cause mouth ulcers.
• Lethargy or weakness. Sleeping more, playing less, seeming flat.

None of these signs on its own means your cat has kidney disease. Increased thirst and weight loss, for example, also happen with other common conditions in older cats, such as hyperthyroidism and diabetes. That is exactly why a vet check matters. If you would like help thinking through what you're seeing, our symptom checker can help you organise your observations before you call.

When to see a vet

Book an appointment if you notice your cat drinking or peeing more than usual, losing weight, eating less, or vomiting more often than before. These are not usually emergencies on their own, but they are worth checking soon rather than waiting to see if they pass.

Contact a vet urgently if your cat:

• stops eating completely for a day or more
• is vomiting repeatedly or can't keep water down
• seems very weak, wobbly or collapses
• is not passing any urine, or is straining in the litter tray with little coming out
• may have chewed or brushed against lilies, or swallowed antifreeze or another toxin

A sudden worsening in a cat already diagnosed with kidney disease is also a reason to call promptly.

How vets diagnose it

Your vet will start by asking about your cat's history and doing a physical examination. They may feel the kidneys through the belly to check their size and shape, look at the gums for paleness, and check the mouth for ulcers.

The main tests are:

• Blood tests. These measure waste products that healthy kidneys normally clear, along with other markers of kidney function, red blood cell levels and important salts and minerals.
• Urine tests. These show how well the kidneys are concentrating urine and whether protein is leaking into it. Urine may also be checked for infection.
• Blood pressure. High blood pressure is common in cats with kidney disease and can harm the eyes, heart and brain, as well as the kidneys themselves, so many vets check it as part of the work-up.

Sometimes your vet may suggest imaging, such as an ultrasound, to look at the kidneys in more detail. Results are often used to "stage" the disease, which helps your vet decide on the most useful treatment and how often to recheck. A single test may not tell the whole story, so repeat tests over time are common.

Treatment and management

Chronic kidney disease usually can't be cured, because damaged kidney tissue doesn't grow back. The good news is that it can often be managed for a long time, and the aim of treatment is to slow its progress and keep your cat feeling as well as possible.

Your vet will tailor a plan to your cat, which may include:

• A vet-prescribed kidney diet. These diets are specially formulated to reduce the workload on the kidneys. Changing food gradually, and offering it warmed, can help fussy cats accept it. It's best to only switch to one of these diets on your vet's advice.
• Fluids. Some cats need fluids given by the vet during a flare-up. Others may benefit from fluids given under the skin at home, which your vet team can teach you to do if it's right for your cat.
• Medicines. Depending on test results, your vet may prescribe treatment to manage blood pressure, protein loss in the urine, nausea, poor appetite, mineral imbalances or anaemia. Always follow your vet's instructions and never give human medicines, as many are dangerous to cats.
• Regular monitoring. Repeat blood tests, urine tests and blood pressure checks help your vet see how things are changing and adjust the plan.

Every cat is different. Some stay stable for a long time with very little change, while others need more frequent adjustments. Your vet is the best person to guide you on what to expect for your own cat.

Prevention

There isn't a reliable way to prevent age-related kidney disease, but there is a lot you can do to give your cat the best chance:

• Regular check-ups. Many vets recommend more frequent health checks for older cats, often including blood and urine tests. Picking up kidney changes early gives the most options.
• Encourage drinking. Cats often don't drink much on their own. Wet food adds water to the diet, and many cats prefer moving water from a pet fountain. Placing several bowls around the house, away from food and litter trays, can also help.
• Keep toxins out of reach. Lilies of all kinds and antifreeze are particular dangers.
• Keep an eye on teeth. Good dental health supports general wellbeing, so ask your vet about it at check-ups.

Living with it

Learning that your cat has kidney disease can feel worrying, but many cats continue to enjoy a good quality of life for a long time. A few simple habits can make a real difference:

• Weigh your cat monthly. Gradual weight loss is one of the earliest signs that things are changing. A baby scale, or weighing yourself with and without your cat, works well. Write the numbers down so you can share them with your vet.
• Keep notes. Jot down appetite, water intake, vomiting and litter tray habits. Small changes are easier to spot on paper.
• Make food appealing. Warming food slightly, offering small fresh portions and keeping bowls clean can help a cat with a reduced appetite.
• Keep water easy to reach. Place fresh water in several quiet spots, especially for older cats who may be stiff.
• Stick to recheck appointments. These are the best way to catch changes before they cause problems.

Our guide to caring for a senior cat has more ideas for keeping an older cat comfortable. Above all, keep talking to your vet. You know your cat best, and your observations at home are a valuable part of their care.