Warning Signs of Chronic Kidney Disease in Cats

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  • At a glance

    • Increased thirst
    • Increased urination
    • Nausea and vomiting
    • Loss of appetite
    • Weight loss
    • Bad breath
    • Mouth ulcers
    • Anemia
    • High blood pressure


    Kidney (renal) disease is a loss of function of the kidneys which are responsible for filtering toxins from the blood. It can be acute (sudden onset) or chronic (slow and progressive). Chronic kidney disease is one of the most common diseases of middle-aged to senior cats. Acute kidney can develop in cats of any age and is commonly associated with a kidney insult (such as a toxin), injury or interruption to the blood flow.

    Kidneys filter out waste products in the blood via the urine. Efficient kidneys can manage this process while preserving as much water as possible.

    By the time symptoms appear, approximately 70% of kidney function will have been lost. This highlights the importance of routine veterinary visits and testing as well as looking out for any changes, no matter how subtle.

    Chronic kidney disease can not be reversed, but it is possible to slow down the progression of the disease with early detection and treatment.

    Increased urination

    As the kidneys lose their ability to filter out toxins, blood flow to the kidneys increases to improve filtration. This, in turn, causes an increase in urination.

    Increased thirst

    The cat drinks more water to compensate for the loss of fluids in the urine, and the cycle continues.

    Nausea and vomiting

    As toxins build up in the blood due to inadequate filtration by the kidneys, nausea develops. Common symptoms of nausea include loss of appetite (below), drooling and vomiting. A one-off vomit, with no other symptoms, is usually of no significance, but any more than that warrants a visit to the veterinarian.


    Anemia is decreased numbers of red blood cells in the blood which are responsible for delivering oxygen to the body tissues. Low numbers of red blood cells can lead to lethargy, rapid breathing, increased heart rate, and pale gums. The kidneys are responsible for the production of erythropoietin, a hormone that instructs the bone marrow to produce red blood cells. Diseased kidneys no longer produce adequate levels of this hormone.

    Loss of appetite and weight loss

    Nausea impacts the cat’s appetite, and as the cat’s appetite wanes, weight loss follows. Weight loss can be subtle and easy to miss, particularly in cats with thick or long coats. I had had two cats lose a significant amount of weight and only picked it up when I picked them up. The cat’s veterinarian should always record the cat’s weight during their annual or bi-annual health checks. I also recommend pet owners evaluate their cat’s overall health every month which should include feeling along the spine and ribs, which reveal weight loss or weight gain.

    Bad breath

    As the kidneys are unable to filter out toxins, levels rise in the blood, which can lead to an ammonia-like smell on the cat’s breath.

    Mouth ulcers

    Open sores on the mucous membranes and tongue in the oral cavity due to toxins that cause pain, drooling and reluctance to eat due to pain.

    High blood pressure

    Unfortunately, most cases of high blood pressure are asymptomatic, but all cats cat over the age of seven should have their blood pressure checked during their annual or bi-annual examination. Left untreated, high blood pressure can further damage the kidneys, harden the arteries and cause a detachment of the retina, which can lead to blindness.

    What can you do?

    If you notice any of the above symptoms, schedule an appointment with your cat’s veterinarian. Early treatment slows down progression, which can extend the cat’s lifespan.

    Diagnostic workup:

    All cats over seven should have bi-annual veterinary checks so that age-related diseases can be picked up and managed in the early stages. We recommend you ask your veterinarian to include the following tests:

    • Blood pressure checks.
    • Biochemical profile, which may reveal elevated levels of blood urea nitrogen (BUN) as well as creatinine.
    • A complete blood count may reveal anemia, which can develop in cats with kidney disease.
    • Urinalysis may reveal a low urine specific gravity, which means the cat’s kidneys have lost their ability to concentrate the urine, and protein in the urine.


    The type of treatment will depend on the stage of kidney disease, and a multimodal approach is most common, to slow down the progression as well as manage symptoms.

    Prescription diet: Kidney diets contain less protein and phosphorus than regular cat food. Cats need protein every day for growth, building muscles and repairing tissue. Urea is a waste product of protein metabolism. Cats with kidney failure are not able to get rid of urea as effectively, which causes a build-up of toxins. Damaged kidneys are also not as efficient at removing phosphorous, which causes high phosphorous in the blood.

    Maintain hydration: Encourage water consumption by ensuring the cat has access to clean drinking water at all times. Some cats can be encouraged to drink more by providing them with a water fountain. If dehydration becomes an issue, it may be necessary to administer fluids subcutaneously (under the skin).

    Anti-nausea: Toxin build-up can cause nausea and loss of appetite. Anti-nausea medication can be prescribed to relieve symptoms.

    Appetite stimulants: This can help cats who have lost their appetite.

    Erythropoietin: Only the human form is available. Some cats may eventually recognise this substance as foreign create antibodies against it.


    • Julia Wilson, 'Cat World' Founder

      Julia Wilson is the founder of Cat-World, and has researched and written over 1,000 articles about cats. She is a cat expert with over 20 years of experience writing about a wide range of cat topics, with a special interest in cat health, welfare and preventative care. Julia lives in Sydney with her family, four cats and two dogs. Full author bio