CONDITION

Chronic Kidney Disease in Cats

A progressive condition where kidney function declines over time, affecting fluid balance, waste filtration, and overall health.

Why this matters now

Chronic kidney disease is one of the most commonly diagnosed conditions in older cats, with prevalence increasing significantly after the age of ten. However, it can also develop in younger cats, sometimes as a consequence of congenital kidney abnormalities, previous urinary tract infections, or toxic exposures. Because the kidneys have substantial reserve capacity, clinical signs often do not become apparent until a considerable proportion of functional tissue has been lost.

The condition typically progresses over months to years, though the rate of decline varies considerably between individuals. Some cats remain relatively stable for extended periods with minimal intervention, while others experience a more rapid deterioration. Progression is often characterised by gradual changes in drinking and urination patterns, body condition, and appetite, punctuated by occasional acute episodes that may temporarily worsen kidney function before stabilising.

Signals & patterns

Early signals

Increased water consumption

A cat that begins drinking noticeably more water than usual, seeking out unusual water sources such as taps or glasses, or spending more time at the water bowl. This reflects the kidneys' reduced ability to concentrate urine, requiring more fluid intake to maintain hydration.

Increased urination

Larger or more frequent urine clumps in the litter tray, or a cat that begins urinating outside the tray. The increased volume is a direct consequence of the kidneys producing more dilute urine as their concentrating ability declines.

Subtle weight loss

A gradual reduction in body condition that may initially be noticed as a more prominent spine or hip bones when stroking the cat. This can develop slowly enough to be overlooked in cats seen daily, and may first be noticed by visitors or during veterinary examinations.

Mild appetite changes

Slight reduction in food intake, increased selectivity about food, or occasional skipped meals. Cats may show interest in food but eat less than usual, or develop new preferences for different textures or flavours.

Later signals

Persistent poor appetite or food refusal

A more consistent reduction in eating, sometimes accompanied by nausea behaviours such as lip-licking, turning away from food after sniffing, or vomiting. This often relates to the build-up of waste products in the blood affecting the gastrointestinal system.

Dull or unkempt coat

Cats may reduce or stop grooming, leading to a dry, rough, or matted coat. This can reflect general malaise, dehydration, or reduced flexibility from muscle wasting, particularly noticeable in cats that were previously fastidious groomers.

Lethargy and withdrawal

Reduced interaction with family members, sleeping more, seeking out quiet or hidden locations, and less interest in activities that previously engaged the cat. These changes may develop gradually and can be attributed to normal ageing.

Oral changes

Bad breath with a distinctive chemical quality, mouth ulceration, or brownish discolouration of the tongue can develop as uraemic toxins accumulate. These signs typically indicate more advanced disease.

Click to read about the biological mechanisms

How this is usually investigated

Investigation of chronic kidney disease in cats typically combines blood and urine testing with imaging to assess kidney structure. A staged approach helps determine the degree of kidney impairment and identify any contributing or complicating factors.

Blood biochemistry

Purpose: Measurement of creatinine, urea, and symmetric dimethylarginine (SDMA) levels in the blood provides an indication of how effectively the kidneys are filtering waste products. SDMA may detect reduced kidney function earlier than traditional markers.
Considerations: Results can be influenced by hydration status, muscle mass, and recent food intake. A single measurement provides a snapshot, and trends over time are often more informative than individual values. Dehydration can make kidney values appear worse than the underlying condition warrants.

Urinalysis

Purpose: Assessment of urine concentration (specific gravity), protein content, and sediment examination helps evaluate the kidneys' ability to concentrate urine and identifies protein loss, infection, or other abnormalities.
Considerations: Urine concentration can vary throughout the day and may be affected by recent water intake. Protein-to-creatinine ratio measurement provides a more standardised assessment of protein loss than a single dipstick reading.

Blood pressure measurement

Purpose: Hypertension is a common complication of chronic kidney disease in cats and can accelerate kidney damage while also affecting the eyes, brain, and heart.
Considerations: Obtaining accurate blood pressure readings in cats can be challenging due to stress in the clinical environment. Multiple measurements and a calm approach help improve reliability. White coat hypertension may produce falsely elevated readings.

Abdominal ultrasound

Purpose: Provides information about kidney size, shape, and internal architecture. Can identify structural abnormalities such as cysts, stones, or tumours, and helps assess whether one or both kidneys are affected.
Considerations: Ultrasound findings provide structural information but do not directly measure function. Small, irregular kidneys are commonly seen in chronic disease, but the appearance does not always predict the rate of progression.

IRIS staging

Purpose: The International Renal Interest Society staging system classifies chronic kidney disease into stages (1-4) based on blood creatinine or SDMA levels, with sub-staging for proteinuria and blood pressure. This helps guide management decisions and monitoring frequency.
Considerations: Staging should ideally be performed when the cat is well-hydrated and clinically stable, as illness or dehydration can temporarily shift values. The stage provides a framework but does not capture the full complexity of each individual cat's situation.

Options & trade-offs

Management of chronic kidney disease in cats typically involves a combination of dietary, medical, and supportive approaches. The emphasis between these options often shifts as the condition progresses, and the most appropriate combination varies between individuals.

Dietary modification

Therapeutic kidney diets are formulated with controlled levels of protein, phosphorus, and sodium, and are often supplemented with omega-3 fatty acids and potassium. These diets aim to reduce the workload on the kidneys and slow the accumulation of waste products.

Trade-offs: Some cats resist dietary changes, particularly if introduced abruptly or during periods of poor appetite. Transitioning gradually and offering multiple kidney diet formulations can help. Forcing a cat onto a diet it refuses may result in inadequate calorie intake, which can be more harmful than the benefits of the specific diet.

Fluid supplementation

Subcutaneous fluid administration at home can help maintain hydration in cats whose fluid intake is insufficient to compensate for their increased urinary losses. This is typically given several times per week using a fluid bag and giving set.

Trade-offs: Home fluid administration requires the owner to learn the technique and the cat to tolerate the process. Some cats accept it readily while others find it stressful. Over-supplementation can occasionally occur, particularly in cats with concurrent heart conditions. Regular monitoring helps determine the appropriate volume and frequency.

Phosphorus management

Dietary phosphorus restriction is usually the first approach, supplemented with intestinal phosphate binders if blood phosphorus levels remain elevated despite dietary control. Phosphorus management aims to slow the progression of kidney damage and prevent secondary hyperparathyroidism.

Trade-offs: Phosphate binders need to be given with meals, which can be challenging with cats that graze throughout the day. Some cats object to the taste or texture of certain binders, and finding an acceptable formulation may require trying several options.

Blood pressure management

Antihypertensive medication, most commonly amlodipine, may be prescribed if blood pressure is consistently elevated. Controlling blood pressure helps protect the kidneys, eyes, and other organs from hypertensive damage.

Trade-offs: Regular blood pressure monitoring is needed to adjust the dose and confirm effectiveness. Some cats experience mild side effects, and the medication represents an additional daily treatment alongside other management components.

Anti-nausea and appetite support

Medications to control nausea and stimulate appetite can help maintain food intake and body condition. Options may include maropitant for nausea, mirtazapine for appetite stimulation, or capromorelin as an appetite stimulant.

Trade-offs: These medications address symptoms rather than the underlying condition. They can be valuable for maintaining quality of life and nutrition, but their effectiveness may diminish as the condition progresses. Appetite stimulants should complement rather than replace efforts to identify and address causes of reduced appetite.

Common misconceptions

Misconception:

"Chronic kidney disease means the cat is in immediate danger"

Reality:

Many cats live comfortably for months to years after diagnosis, particularly when the condition is identified early and managed appropriately. The rate of progression varies significantly between individuals, and some cats with early-stage disease may remain stable for extended periods.

Misconception:

"Drinking more water is a good sign in cats"

Reality:

While adequate hydration is important, noticeably increased water consumption in cats is often a significant clinical sign rather than a positive behaviour. Cats are naturally efficient at concentrating their urine, so a marked increase in drinking typically warrants investigation rather than encouragement.

Misconception:

"Kidney disease is always caused by a poor diet"

Reality:

The underlying cause of chronic kidney disease in cats is often not identified. While some cases may relate to previous infections, toxin exposure, or other identifiable factors, many develop without a clear precipitating cause. The condition appears to have a strong association with ageing processes in the feline kidney, and certain breeds may carry a genetic predisposition.

Understanding the patterns of chronic kidney disease in an individual cat often develops over time through monitoring and observation. Changes in drinking habits, appetite, weight, and general demeanour can all provide useful information. Many cats with kidney disease can maintain a good quality of life for considerable periods, and the approach to management often evolves as the condition and the cat's responses become better understood.

Last reviewed: 24 April 2026 · Dr Alastair Greenway MRCVS