Signs of Kidney Decline in Cats: Could the Changes You're Seeing Be Related to Kidney Health?

Is your cat drinking more water? Urinating more often? Eating less or losing weight?

These changes can have many causes, but they can also be signs of declining kidney function, a common health concern in older cats.

Up to 40% of cats over age 10
are affected

Up to 80% of cats over age 15
are affected

Early Signs May Include:

  • Increased thirst
  • Increased urination
  • Changes in appetite
  • Weight loss

As Kidney Decline Progresses, You May Notice:

  • Less energy or lethargy
  • Vomiting or nausea
  • Dehydration
  • Poor or unkempt coat
  • Weakness

More Serious Signs Can Include:

  • Pale gums
  • Disorientation
  • Vision changes
  • Significant changes in urination

Start Supporting Your Cat's Kidney Health Today

How Is Kidney Function Evaluated in Cats?

You cannot assess your cat’s kidney health based on symptoms alone. Your veterinarian will look at your cat’s overall health and use blood and urine testing to evaluate how well the kidneys are working.

The good news is that testing can identify changes in kidney function early, even when outward signs are still subtle.

Testing May Include:

  • Bloodwork: Measures markers such as BUN, creatinine, and SDMA that help show how well the kidneys are filtering waste.
  • Urinalysis: Evaluates how well the kidneys concentrate urine and checks for other abnormalities.
  • Blood Pressure: Checks for high blood pressure, which can be associated with kidney problems.
  • Urine Protein Testing: Checks for abnormal protein loss through the kidneys.
  • Additional Testing: Imaging or other tests may provide a more complete picture of your pet’s kidney health.

What Do Your Cat's Kidney Blood Test Results Mean?

Seeing BUN, creatinine, and SDMA on your cat’s lab report can be confusing. Each gives your veterinarian information about how well the kidneys are doing their job.

BUN: Blood Urea Nitrogen
Measures a waste product that the kidneys normally help remove from the blood. Higher levels can occur when kidney function declines, but BUN can also be affected by other factors.

Creatinine: A Marker of Kidney Filtration
Creatinine is a waste product normally filtered by the kidneys. Rising levels can be a sign of reduced kidney filtration, although hydration and muscle mass can affect the result.

SDMA: An Early Indicator of Kidney Changes
SDMA (Symmetric Dimethylarginine) is a marker of kidney filtration that may increase earlier than creatinine as kidney function declines and is less affected by muscle mass.

Your veterinarian won’t rely on one number alone.
Bloodwork, urine testing, clinical signs, and changes over time are considered together.

What Happens Next? Understanding Your Cat's Kidney Health

When a veterinarian confirms a chronic kidney condition, they may use the four-stage system developed by the International Renal Interest Society (IRIS) to assess its severity. Bloodwork, urine testing, and other findings help determine the stage and guide appropriate care.

Stage 1

Early Kidney Changes

Bloodwork may still appear normal, but urine testing or other findings can reveal early kidney changes. Few or no outward signs may be present.

Stage 2

Mild Kidney Decline

Waste levels may begin to rise in the blood. Some cats may drink or urinate more, while others show no obvious signs.

Stage 3

Moderate Kidney Decline

Waste buildup becomes more significant. Changes in appetite, weight, energy, or hydration may become noticeable.

Stage 4

Advanced Kidney Decline

The kidneys have significantly reduced filtering ability. Nausea, poor appetite, weakness, and dehydration may become more pronounced.

Why Does Staging Matter?

Knowing the stage, along with factors such as blood pressure and protein in the urine, helps your veterinarian determine the appropriate treatment, nutrition, and monitoring for your cat.

Support Your Cat's Kidney Health with Renaphil™

When you notice changes in your cat’s kidney health, it’s natural to wonder,“What can I do to help?”

You can take an active role in supporting your cat’s kidney health. Renaphil gives you a proactive way to start.

Developed for pets experiencing kidney decline or age-related changes in kidney health, Renaphil takes a gut-based approach to help maintain healthy kidney function and support long-term kidney health, helping your cat stay healthier and feel more like themselves longer.

And it’s easy to make Renaphil part of your cat’s daily routine. Available in convenient powder and pill forms, Renaphil is given twice daily to provide ongoing kidney support.

Frequently Asked Questions About Kidney Health in Cats

Why are kidney problems so common in older cats?

Kidney problems become more common as cats age, although veterinarians do not always know exactly why. In many cases, the underlying cause of declining kidney function is never identified.

Several factors may contribute, including genetics, inherited kidney conditions, and gradual damage to the kidneys over time. As cats live longer, they are also more likely to experience age-related changes that affect how well their kidneys work.

Kidney function can decline for several reasons, including aging, genetics, infections, high blood pressure, exposure to toxins, and other underlying health conditions. In some cats, the exact cause may never be known.

As cats get older, their kidneys may gradually become less efficient at filtering waste from the bloodstream and maintaining the body’s fluid and mineral balance. Because these changes often develop

Kidney decline refers to a reduction in how effectively the kidneys perform their normal functions, including filtering waste and maintaining fluid balance. This decline can range from mild changes to more advanced loss of function.

Kidney failure generally refers to a more serious loss of kidney function, when the kidneys can no longer adequately perform these essential tasks. Kidney failure may develop gradually or occur suddenly.

Recognizing changes in kidney function early can help your veterinarian recommend appropriate care and monitoring.

Yes. Cats can experience changes in kidney function long before showing noticeable signs. In fact, cats are particularly good at hiding signs of illness.

Routine veterinary examinations, blood tests, urine tests, and blood pressure measurements can help identify changes before obvious symptoms develop. Tests may include creatinine, blood urea nitrogen (BUN), and symmetric dimethylarginine (SDMA), a marker that can help detect reduced kidney function earlier in some cats.

Regular screening is especially important for senior cats and those with risk factors for kidney problems.

Yes. Many cats with declining kidney function continue to enjoy a good quality of life, especially when changes are identified early and managed appropriately.

Veterinary care, proper nutrition, hydration, and ongoing monitoring can help support your cat’s comfort and overall health.

Renaphil™ offers an additional way to support kidney health. Its patented probiotic formula works in the gut to help reduce certain waste compounds, supporting the kidneys as part of a comprehensive kidney health routine.

There is no single answer. Some cats live for several years with declining kidney function, while others experience more rapid changes.

Life expectancy depends on several factors, including the extent of kidney function loss, your cat’s age, other health conditions, and how well your cat responds to care.

Early detection, appropriate nutrition, veterinary treatment, and regular monitoring can help support quality of life and may improve long-term outcomes.

Taking an active interest in your cat’s kidney health is an important first step. Because kidney changes can develop without obvious signs, even attentive pet owners may not recognize a problem right away.

Regular veterinary visits, appropriate nutrition, fresh water, and awareness of changes in drinking, urination, appetite, or weight can all make a difference.

You can also ask your veterinarian about additional nutritional support, including Renaphil, a daily kidney probiotic scientifically formulated to help maintain healthy kidney function.

Supporting your cat’s kidney health starts with a few important habits:

  • Schedule regular veterinary checkups to monitor kidney health and identify changes early.
  • Encourage proper hydration by providing fresh water and considering wet food.
  • Provide appropriate nutrition based on your cat’s age, health, and individual needs.
  • Watch for changes in drinking, urination, appetite, weight, and activity.
  • Consider additional kidney support. Ask your veterinarian about Renaphil, a patented kidney probiotic formulated to support kidney health by working in the gut.

While not all causes of kidney decline can be prevented, proactive care can help support your cat’s overall health and address problems early.

The right diet depends on your cat’s age, overall health, and kidney function.

For cats with reduced kidney function, veterinarians may recommend a specially formulated diet with controlled phosphorus levels, appropriate amounts of high-quality protein, and balanced minerals. These diets are designed to help manage the demands placed on the kidneys while maintaining proper nutrition.

Adequate hydration is also important. Wet food can help increase water intake, particularly for cats that do not drink much water on their own.

Before making significant dietary changes, talk with your veterinarian to determine what is best for your cat.

What Else Should You Do For Your Pet’s Kidney Health? Talk to Your Veterinarian.

It’s never too early to talk to your veterinarian about your cat’s kidney health.

Noticing changes in your cat? Kidney decline can develop gradually, often before obvious signs appear. A veterinary exam and testing can help determine what may be happening and identify steps you can take to support your cat’s kidney health.

No signs of kidney problems? Kidney health still matters. Renaphil was developed for pets experiencing kidney decline or age-related changes in kidney health, as well as those who may benefit from proactive kidney support. Ask your veterinarian whether Renaphil may be right for your cat.

Help Support Your Cat's Kidney Health Today

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