Kidney Failure in Cats: Symptoms, Diagnosis, & Treatment

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Kidney Failure in Cats Feature

With old age in cats comes age-related health problems. One of these problems is kidney failure, a progressive disease defined by a significant loss of kidney function.

Kidney failure in cats is a big topic, so we’re going to cover a lot of material in this article. We’ll start with some background about the kidneys, then take a deep dive into the nuts and bolts of kidney failure.

Kidney Basics

Cat Kidney Basics

The kidneys are bean-shaped organs responsible for several vital functions, including filtering toxins and waste out of your cat’s bloodstream, producing urine, regulating the blood’s levels of nutrients, and conserving water.

The kidneys are bean-shaped organs inside a cat’s abdomen. They’re not very big, but they pack a powerful punch in maintaining a cat’s health. Here are their major functions: (1) filter toxins and waste products out of the blood; (2) produce urine to get rid of those toxins and waste products; (3) regulate blood levels of essential nutrients, such as calcium and phosphorus; and (4) conserve water.

Different parts of the kidney’s anatomy carry out these functions. For example, nephrons (kidney cells) are responsible for the filtration. The ureters carry urine from the kidneys to the bladder.

Given these essential functions, you can imagine that kidney failure can be a serious blow to a cat’s overall health.

Fortunately, kidneys don’t fail easily. They have lots of reserve capacity, meaning that they can continue functioning relatively well despite suffering some damage.

How Does Kidney Failure Occur?

Kidney failure occurs when at least two-thirds of each kidney is damaged. With this much damage, the kidneys cannot perform their essential functions.

Kidney failure can be acute or chronic.

Acute kidney failure occurs when the kidneys suddenly stop working. Some of the many causes of acute kidney failure are toxin ingestion (e.g., antifreeze) and shock.

Chronic kidney failure, also called chronic kidney disease, develops over many years. It usually begins when cats are about six years old and becomes progressively worse as the nephrons slowly die. When more nephrons die than can be replaced, kidney failure becomes apparent.

Chronic kidney failure is much more common than acute kidney failure in cats, so we’ll focus on chronic kidney failure.

What Causes Chronic Kidney Failure?

The exact cause of chronic kidney failure remains unknown. However, many health conditions, such as those listed below, can significantly damage the kidneys over time.

  • Kidney cancer
  • Kidney stones
  • Bacterial infection
  • Hypertension (high blood pressure)
  • Systemic infection (e.g., bladder, lungs)
  • Polycystic kidney disease: fluid-filled cysts that replace a kidney’s normal internal anatomy

What Are The Clinical Signs Of Kidney Failure?

Kidney Failure in Cats Symptoms Cat in Litter Box

Excessive thirst and urination are among the most recognizable symptoms of kidney failure in cats.

Even when the kidneys are failing enough to cause clinical signs, kidney failure may not be the obvious diagnosis. Kidney failure’s clinical signs are non-specific, meaning that they don’t indicate a particular disease.

The clinical signs gradually worsen as kidney failure progresses.

Below Are Signs Of Early Kidney Failure, Also Called Compensated Kidney Failure:

At this stage, the kidneys compensate for their inability to filter out waste products by producing more urine.

  • Increased urination
  • Increased thirst

Below Are Signs Of Advanced Kidney Failure, Known As Uncompensated Kidney Failure:

At this point, the kidneys can’t compensate for their loss of function. Uremia, which is the life-threatening buildup of toxins and waste in the blood, develops and causes severe clinical signs.

  • Reduced appetite
  • Weight loss
  • Poor coat
  • Bad breath
  • Vomiting
  • Weakness
  • Lethargy
  • Depression
  • Pale gums
  • Mouth ulcers

How Is Kidney Failure Diagnosed?

Kidney Failure in Cats Diagnosis Cat at Veterinarian

Your veterinarian can diagnose your cat with kidney failure through bloodwork and urinalysis.

Because kidney failure affects older cats, the clinical signs listed above may be mistaken for normal old-age changes.

Diagnostic testing for kidney failure primarily involves bloodwork and a urinalysis.

Several Changes On The Bloodwork Suggest Kidney Failure:

  • Increased blood urea nitrogen (BUN) and creatinine levels: BUN and creatinine are waste products that normal-functioning kidneys easily eliminate.
  • Reduced potassium
  • Elevated phosphorus
  • Anemia (low red blood cell count)

A relatively new blood test that measures a substance called SDMA helps to diagnose kidney failure even earlier than can be done with routine bloodwork.

On a urinalysis, dilute urine would suggest kidney failure, especially if the bloodwork shows elevated BUN and creatinine. Protein may also be present in the urine.

Because hypertension can cause kidney failure, a veterinarian may also take a cat’s blood pressure to help confirm a kidney failure diagnosis.

What Are The Stages Of Kidney Failure?

An official staging system, developed by the International Renal Interest Society (IRIS), assigns a stage to chronic kidney failure according to fasting blood creatinine levels. There are also sub-stages, which consider blood pressure and protein in the urine.

The main stages are 1 (least severe) to 4 (most severe). Your cat’s stage of kidney failure will guide treatment.

You can find the most recent IRIS staging guidelines here.

How Is Kidney Failure Treated?

cat receiving subcutaneous fluids

While not curable, kidney failure in cats is treated using a range of therapies, with most aiming to reduce the kidneys’ workload, minimize waste products in the blood, replace lost nutrients, and manage clinical signs.  Subcutaneous fluids are often administered to cats who have become dehydrated.

Chronic kidney failure is not curable. Treatment goals include reducing the kidneys’ workload, minimizing waste products from the blood, replacing lost nutrients, and managing clinical signs.

Treatments can generally be grouped into dietary changes and medications. Be aware that not every cat in kidney failure will need every available treatment.

Dietary Changes

The ideal kidney diet is low in protein, phosphorus, and sodium. A low-protein diet is needed to reduce the kidneys’ workload, but the protein must be of high quality. Phosphorus must be kept low because it can accumulate in the blood when the kidneys are failing. Low sodium is necessary because hypertension can worsen kidney function.


Cats in kidney failure need easy access to plenty of fresh water to prevent dehydration. However, kidney failure can make a cat feel lousy and not in the mood to drink water. Adding some flavor to the water, such as some low-sodium flavored broth, can entice a cat to drink.

For cats with severe chronic kidney failure, daily subcutaneous fluids may be necessary to maintain adequate hydration. Don’t worry—giving subcutaneous fluids to your cat is easy to do and is comfortable for your cat.


In kidney failure, nutrients such as potassium and vitamins B and C are lost through the urine and need to be supplemented back into the diet. They can be given as daily supplements or included in the kidney diet.

Other supplements include antioxidants and fatty acids to reduce further kidney damage.

Your veterinarian will determine which supplements your cat will need and instruct you on how to add them to your cat’s diet.


An array of medications helps to manage kidney failure in cats. For example, anti-vomiting medications may be needed to control a cat’s vomiting.

Phosphate binders attach to phosphate in the intestine and prevent it from getting absorbed into the bloodstream.

Erythropoietin, which stimulates red blood cell production, improves anemia.

Blood pressure medications reduce blood pressure and improve blood flow through the kidneys.

As with your cat’s diet, your veterinarian will determine which additional medications your cat will need.

What’s The Prognosis For Kidney Failure?

The prognosis depends on the severity of kidney failure. Kidney failure will progressively worsen, but the treatments listed above can slow down the progression and give your cat a good quality of life even as their kidneys aren’t working so well.

Bringing It Together

Kidney failure is a complicated but manageable disease in older cats. If your cat is in kidney failure, work with your veterinarian and do your best to care for your cat.

Frequently Asked Questions

What are the symptoms of end-stage kidney failure in cats?

The symptoms of end-stage kidney failure reflect the kidneys’ inability to compensate for significant damage and loss of function. These symptoms include vomiting, weakness, depression, weight loss, and bad breath.

How long does a cat live with kidney failure?

This depends on the stage of kidney failure. A cat may live several years with early-stage kidney failure, but less than that if the kidney failure is advanced.

Is kidney failure painful in cats?

That can depend on the underlying cause of kidney failure. For example, antifreeze toxicity can lead to a painful swelling of the kidneys.

Is kidney failure reversible?

The kidneys can withstand a lot of damage before they start to fail. However, once kidney failure sets in, there’s little chance for the kidneys to recover. Therefore, kidney failure is not reversible.

JoAnna Pendergrass, DVM

About JoAnna Pendergrass, DVM

JoAnna Pendergrass, DVM, is a veterinarian and freelance medical writer in Atlanta, GA. After graduating from the Virginia-Maryland College of Veterinary Medicine with her veterinary degree, JoAnna completed a 2-year research fellowship in neuroscience at Emory University. During this fellowship, she learned that she could make a career out of combining her loves of science and writing. As a medical writer, JoAnna is passionate about providing pet parents with clear, concise, and engaging information about pet care. Through her writing, she strives not only to educate pet parents, but also empower them to make good health decisions for their pets. JoAnna is a member of the American Medical Writers Association and Dog Writers Association of America.

14 thoughts on “Kidney Failure in Cats: Symptoms, Diagnosis, & Treatment

  1. AvatarKelly Ingegniero

    I believe our kitty is at the very end of renal failure. He no longer eat no matter what we give him, even though a syringe.He’s
    always on my cushion so I have moved to a different place. He lays around all day doing nothing. He’s lost a lot of weight as well. We feel he has no quality of life left. He was diagnosed 1 1/2 years ago. He is 17 and think it’s time. Any thoughts would be greatly appreciated.

    1. JoAnna Pendergrass, DVMJoAnna Pendergrass, DVM Post author

      Hi Kelly,

      I’m so sorry to hear about your cat. Quality of life is a big consideration when a pet has become very ill. I suggest that you talk with your veterinarian about your cat’s declining quality of life. Unfortunately, it’s never easy to talk about the end of a pet’s life. Your veterinarian would be the best person to talk to because they know your cat so well and can help you make a decision. Remember that it is your decision to make; your vet is simply there to help guide you through the decision-making process.

  2. Avatarsheldon abrams

    My cat is 13 year old Maine Coon with less than 25% kidney function. He howls a lot when getting ready to drink his water.
    He drinks a great deal and urinates many times a day.
    His appetite is still good but I’m concerned he may be in pain.

    1. JoAnna Pendergrass, DVMJoAnna Pendergrass, DVM Post author

      Hi Sheldon,

      Cats often vocalize when they are in pain or have discomfort. However, pain is not typically associated with kidney failure. I recommend notifying your veterinarian about the behavior. It could be that your cat has some underlying pain that hasn’t yet been diagnosed.

  3. Avatarnancy l elston

    My cat has been diagnosed with kidney failure. He had one seizure 3 days ago. Is that a symptom of kidney failure and will he have more.


    1. JoAnna Pendergrass, DVMJoAnna Pendergrass, DVM Post author

      Hi Nancy,

      Seizures can occur with kidney failure. They can occur because, as kidney function worsens, toxins build up in the blood (‘toxemia’). Toxemia could eventually lead to neurologic problems, such as seizures. There’s not a good way to know for sure whether your cat will have more seizures. If you have not done so already, let your vet know that your cat has had a seizure. Your vet will be able to provide the best way to move forward, which may include additional medical therapy.

  4. AvatarPam

    Can we get the suppliments ourselves or does it have to be through a vet? My cat is 18 and I just can’t put her through the stress of taking her to the vets office.

    1. JoAnna Pendergrass, DVMJoAnna Pendergrass, DVM Post author

      Hi Pam,

      It’s understandable that you don’t want to increase your cat’s stress with a vet visit. I recommend calling your vet and asking them which specific supplements your cat needs, and which brand of supplement that they recommend. Your vet can also instruct you on how much of each supplement to give your cat, and how to administer it. If you want to purchase the supplements online, go to trustworthy websites, such as Chewy.

  5. AvatarJoy Morgal

    My cat is at least17 years old.He was diagnosed about 54years ago. He was a stray who showed up one cold winter day.He was pretty fat had been neutered an am just assuming had been vaccinated.He wss super thirsty ANF needed or demanded moving water from the tap.I took him for a check up and we made it. Barely thru that. I didn’t take hi back much.Worst visit he was in kidney make sure begets plenty of water his appetite is hood.his belly is very big and he has lost a lot of his teeth but for an old cat with issues he is pretty good.Taking him yo the vet usually results in me bleeding and crying I am 75 and just want to know if you think my Perry is in pain or misery He is an amazing cat except at the vets.

    1. JoAnna Pendergrass, DVMJoAnna Pendergrass, DVM Post author

      Hi Joy,

      From your description, I’m not able to say definitively if Perry is in pain or misery. Because it seems that visits to the vet could be causing Perry a lot of stress, you could try to find ways to make the visits less stressful. For example, you could make the car ride to the vet comfortable, such as by making sure Perry is secure in his crate and playing calming music in the car. At the vet’s office, your vet could try different things to keep Perry’s stress level down. I recommend talking to your vet before your next visit to come up with a plan make the visit more pleasant for you and Perry.

  6. AvatarKatherine Boyd

    I adopted my 5-year-old cat, who has FIV, from a rescue two months ago. He was on the street before the rescue found him. A recent blood test revealed that his kidneys are functioning at only 25% capacity. His creatinine and BUN levels were off the charts. He was in the hospital on IV fluids for 3 days and a subsequent blood test showed his levels had “improved.” Now that he’s off the IV, however, his appetite and energy have again decreased. He refuses to eat the canned Royal Canin kidney food; he does eat a bit of the dry. To the best of my knowledge, he hasn’t ingested any toxins. I know kidney failure is incurable and irreversible. The vet doesn’t know why a young cat would get kidney disease and wants to perform an ultrasound to find out if it’s congenital or if it’s cancer. What else could an ultrasound tell us? Is there any point to his having one if he isn’t going to get any better?

    1. JoAnna Pendergrass, DVMJoAnna Pendergrass, DVM Post author

      Hi Katherine,

      I’m sorry to hear about your cat. An abdominal ultrasound can be used to see if there are any visible abnormalities with the kidneys, such as smaller-than-normal size, mineralization (calcium buildup, for example), and damage to the soft tissue inside the kidneys. Although your cat won’t necessarily get better because of the ultrasound, your vet may be able to adjust your cat’s treatment management according to how the kidneys look on the ultrasound. I think that it would be worth it to have the ultrasound performed to, quite literally, get a better look at the kidneys and more fully understand your cat’s kidney disease.


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