Kidney Failure in Cats. The Warning Signs You Need to Know


Kidney failure, also known as renal failure, is a common condition in cats that occurs when the kidneys are no longer able to effectively filter waste products from the blood. This results in a buildup of toxins in the body which can make cats very sick.

It’s important for cat owners to recognize the early signs of kidney failure, as the sooner treatment begins, the better the outcome typically is. Identifying kidney failure early provides the best chance to slow progression of the disease and keep cats comfortable for as long as possible.

There are two main types of kidney failure in cats: acute kidney failure, which comes on suddenly, often caused by ingesting toxins or trauma; and chronic kidney disease, which comes on gradually over time as the kidneys slowly lose function. Both types have similar clinical signs but different causes and treatments.

This article will discuss the most common symptoms of kidney failure in cats so owners know what signs to look out for. Recognizing these symptoms early is key to getting cats the treatment they need.

Increased Thirst and Urination

One of the earliest signs of kidney failure in cats is increased thirst and urination. As the kidneys struggle to function properly, they are less able to concentrate urine. This leads to increased urination as the body tries to excrete more water. To compensate for the increased fluid loss, cats will drink more water. According to (, “excessive drinking and urinating are early signs as the kidneys struggle to function.” This increase in thirst and urination is known as polydipsia and polyuria.

Cat owners may notice their cat drinking significantly more water than usual. The litter box will also contain larger amounts of more dilute urine. Cats may start having accidents outside the litter box as they struggle to hold their urine. As the disease progresses, the increase in thirst and urination will become even more pronounced. Catching this symptom early is important, as it can indicate kidney dysfunction before other signs appear.

Weight Loss

Weight loss is a common symptom of kidney failure in cats. As the kidneys fail to properly filter waste from the bloodstream, toxic buildup often leads to nausea and loss of appetite. However, cats with kidney disease may also experience weight loss despite having a normal appetite and eating well. This is because the kidneys play an important role in metabolizing protein. Damaged kidneys allow protein to escape through the urine, depriving the body of this essential nutrient even when calorie intake remains stable. The resulting protein deficiency causes muscle wasting and rapid weight loss. According to the Ormond Cat Clinic, “This protein loss, along with a poor appetite, can lead to weight loss. Weight loss is often the first and only sign seen in cats with chronic renal disease.” [1] Restoring protein balance through diet is crucial, but difficult, as cats with kidney disease often have reduced appetites. Weight loss despite normal eating is a key sign of advanced kidney failure in cats.

Loss of Appetite

Kidney dysfunction can cause nausea and changes in taste that reduce appetite. Cats with kidney disease often eat less or stop eating because they feel too sick to eat. Toxins build up in the bloodstream when the kidneys aren’t working properly, which can make cats feel nauseous. Changes in taste are also common, as wastes accumulate in the mouth and alter the taste of food. According to, loss of appetite is one of the most obvious symptoms of kidney disease in cats.

As cited at, “Cats who are dealing with kidney disease or kidney failure will likely not feel like eating very much. They may be completely turned off to their favorite foods.”


One of the most common symptoms of kidney failure in cats is lethargy, or fatigue. As the kidneys fail to remove waste products from the bloodstream, it can make cats feel generally unwell. Toxins building up in the body contribute to overall weakness and a lack of energy. Cats with kidney disease often sleep more and have less interest in playtime or interactive toys and games.

Kidney failure contributes greatly to lethargy and fatigue in cats. The buildup of toxins often leaves cats feeling run down. They may have trouble getting up, moving around, and going about their normal activities. Lethargy from kidney failure can range from mild to severe depending on how far the disease has progressed. In the later stages, cats may spend most of their time sleeping and have very little interest in anything else.

If you notice your cat sleeping more often and not engaging in activities they used to enjoy, lethargy could signal an underlying kidney problem. It’s important to have your vet run tests if fatigue comes on suddenly or gets progressively worse. Addressing the kidney failure can help minimize toxins in the body and restore some energy levels in cats.

Poor Coat Condition

As kidney disease progresses in cats, their coats often become dull, dry and unkempt. This is due to the kidneys’ inability to properly regulate nutrients and maintain hydration in the body. When the kidneys start to fail, they are unable to filter out waste products from the bloodstream efficiently. This causes an accumulation of toxins in the body that can lead to poor coat health.

Unkempt and dull coats in cats with kidney disease are typically caused by mineral and nutrient imbalances. Healthy kidneys produce erythropoietin, which stimulates red blood cell production. Kidney failure reduces erythropoietin, leading to anemia and reduced oxygen circulation. This contributes to poor skin and coat condition. The kidneys also regulate electrolyte levels like calcium and phosphorus. Imbalances in these minerals can make the skin dry and the coat brittle.

In addition, reduced appetite and nausea from uremic toxins lead to reduced protein intake. Protein is essential for skin and coat health. Without adequate protein, the cat’s hair quality deteriorates. Dehydration from increased thirst and urination also causes dry, flaky skin and a dull, unkempt coat.

If cat owners notice a dull, brittle coat or matted fur, it is important to have a veterinarian run tests for kidney disease. Addressing nutrient imbalances and hydration issues may help improve coat condition. However, the underlying kidney disease will continue to progress.


Bad Breath

As kidney function declines, toxins build up in the bloodstream. This can lead to mouth ulcers and very foul-smelling breath. According to AVIM (, the bad breath associated with kidney disease often has an ammonia odor due to the buildup of urea and other toxins.

VCA Animal Hospitals ( notes that halitosis (bad breath) is a common symptom of chronic kidney disease in cats. The foul odor is described as similar to urine or ammonia.

Mouth ulcers combined with the kidney’s inability to eliminate toxins leads to very foul breath in cats with kidney failure. Owners describe the breath as extremely pungent with an ammonia-like smell.


As kidney failure progresses in cats, toxins build up in the bloodstream. This condition is known as uremia. The uremic toxins can irritate the stomach lining and cause nausea and vomiting.

Uremia leads to increased stomach acid production which causes stomach ulcers. These ulcers make cats feel nauseous, resulting in vomiting and loss of appetite (PetMD).

Vomiting may happen sporadically or frequently in cats with kidney failure. The vomit may be clear or may contain food, bile or blood. Persistent vomiting can lead to weight loss, electrolyte imbalances and dehydration.

Medications can help control vomiting and make cats feel better. Anti-nausea drugs like maropitant (Cerenia) can reduce vomiting episodes. Drugs that reduce stomach acid like famotidine (Pepcid) can help heal ulcers and improve appetite (Iris Kidney).


One of the symptoms of kidney failure in cats is diarrhea. This is because the kidneys play an important role in regulating fluid balance in the body. When the kidneys start to fail, they are no longer able to maintain the correct balance of fluids. As a result, excess water ends up in the gut, leading to loose, watery stools. Cats with kidney failure often develop chronic diarrhea that may contain traces of blood.

According to Guilford-Jamestown Veterinary Hospital, diarrhea containing blood is a common symptom in cats with kidney failure. The kidneys are responsible for filtering waste products from the blood. When they are damaged, these waste products build up and may leak into the gut, resulting in bloody diarrhea.

In summary, difficulty regulating fluid levels is a major cause of diarrhea in cats with kidney failure. The kidneys are no longer able to maintain the correct balance of fluids, leading to excess water in the gut and chronic, watery diarrhea. This diarrhea may also contain blood due to waste products from the blood filtering into the gut.

When to See a Vet

If your cat is displaying multiple symptoms of kidney failure, it is important to schedule an appointment with your veterinarian as soon as possible. Some key signs that warrant a trip to the vet include:

Lethargy and lack of appetite for more than 24 hours (

Significant increase in water consumption and urination (

Repeated vomiting or diarrhea

Weight loss

Poor coat condition

Bad breath

Inability to walk properly

The combination of multiple symptoms is a clear sign that your cat requires medical attention. Kidney disease is progressive if left untreated, so early detection and treatment is key to slowing the disease and preserving kidney function for as long as possible.

Consulting your vet promptly when these signs arise can help avoid complications and improve your cat’s quality of life even in advanced stages of kidney failure.

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