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Understanding Kidney Disease in Dogs: The 4 Stages and What They Mean

Hearing that your dog has kidney disease can be scary. You may suddenly be facing new terms, lab numbers, and treatment plans—and wondering what it all means for your dog’s comfort and future.

Veterinarians often use guidelines from the International Renal Interest Society (IRIS) to “stage” chronic kidney disease (CKD). These stages help describe how advanced the disease is and guide decisions about diet, medications, and monitoring.

This guide walks through the 4 IRIS stages in plain language so you can better understand what’s happening in your dog’s body and how you can help.

What Are IRIS Stages in Dogs?

The IRIS staging system is a framework vets use to classify kidney disease based on:

  • Blood tests (especially creatinine and SDMA)
  • Urine concentration and protein levels
  • Blood pressure and other findings

Each stage (1–4) reflects a different level of kidney function:

  • Stage 1: Early changes, often no symptoms
  • Stage 2: Mild kidney dysfunction, subtle signs may appear
  • Stage 3: Moderate kidney failure, clear clinical signs
  • Stage 4: Severe kidney failure, advanced symptoms

Your veterinarian will explain your dog’s specific stage and tailor a plan to their age, overall health, and how they’re feeling—not just the numbers on the lab report.

Stage 1: Early Changes (Often No Obvious Symptoms)

In Stage 1, the kidneys are starting to struggle, but they’re still keeping up fairly well. Most dogs:

  • Look and act completely normal
  • Have normal or near-normal creatinine levels
  • May show a slight rise in SDMA (an early kidney marker)
  • Might have subtle changes in urine concentration or kidney imaging

Because your dog usually feels fine, Stage 1 is easy to miss without routine blood and urine testing—especially in senior dogs.

What your vet might recommend in Stage 1:

  • More frequent blood and urine checks
  • Monitoring blood pressure and urine protein
  • Early diet adjustments or supplements in some cases
  • Addressing any underlying issues (e.g., infections, dental disease, high blood pressure)

Catching kidney disease at this stage gives you and your vet the best chance to slow its progression.

Stage 2: Mild Kidney Disease – The First Red Flags

By Stage 2, the kidneys have lost more function, but many dogs still seem fairly well overall.

You may notice:

  • Drinking more water than usual
  • Peeing larger volumes or more often
  • Possibly mild weight loss or picky eating

Bloodwork usually shows a mild to moderate increase in kidney values, and your vet may be more confident that CKD is present rather than just “borderline” changes.

Common recommendations at Stage 2:

  • Transition to a kidney-supportive diet
  • Regular monitoring (bloodwork, urine tests, blood pressure)
  • Possible medications to:
    • Control blood pressure
    • Reduce protein loss in urine
    • Manage nausea or appetite changes if present

Many dogs can stay in Stage 2 for a long time, especially with early intervention and consistent care.

Stage 3: Moderate Kidney Failure – Managing Quality of Life

In Stage 3, the kidneys are significantly compromised. Their ability to filter waste and balance fluids and minerals is clearly reduced.

You may see more noticeable symptoms, such as:

  • Decreased appetite or reluctance to eat
  • Weight loss and muscle thinning
  • Lethargy or less interest in play and walks
  • Bad breath or mouth ulcers in some dogs
  • Occasional vomiting or nausea

Blood tests show higher levels of waste products (like creatinine and BUN), and your vet will typically shift focus to active management of both the disease and your dog’s comfort.

Typical Stage 3 care may include:

  • Strict adherence to a renal diet
  • Medications for:
    • Nausea and vomiting
    • Stomach acid reduction
    • Blood pressure and proteinuria control
  • Subcutaneous fluids at home in some cases (fluids given under the skin to support hydration)
  • More frequent rechecks to adjust the plan as needed

The goal at this stage is to maintain a good quality of life for as long as possible—keeping your dog comfortable, eating, and enjoying daily routines.

Stage 4: Advanced Kidney Failure – Focus on Comfort

Stage 4 represents severe kidney failure. At this point, the kidneys are no longer able to keep up with their job of filtering toxins and balancing fluids and electrolytes.

Common signs include:

  • Marked weight loss and muscle wasting
  • Persistent or frequent vomiting
  • Little to no appetite
  • Profound lethargy, weakness, or disorientation
  • Bad breath, mouth ulcers, or a chemical-like odor
  • Changes in urination (sometimes more, sometimes less)

Bloodwork in Stage 4 shows very high kidney values and signs that the body is struggling to cope.

Care at Stage 4 generally focuses on:

  • Keeping your dog as comfortable and nausea-free as possible
  • Supporting hydration and nutrition in whatever way is still tolerated
  • Carefully weighing the benefits and burdens of each treatment
  • Honest discussions about quality of life and end-of-life planning

A common question is: “How long can a dog live with Stage 4 kidney disease?”
There’s no single answer. Some dogs may only have weeks, while others can live for several months with attentive, individualized care. What matters most is how your dog feels each day.

How Fast Does Kidney Disease Progress in Dogs?

The speed of progression varies widely from dog to dog. Some stay in the earlier stages for years; others may move from mild to advanced disease more quickly.

Progression can be influenced by:

  • Age and breed
  • Other health issues (e.g., heart disease, infections)
  • Blood pressure and protein levels in the urine
  • Diet and hydration
  • How consistently medications and monitoring are done

Regular checkups and follow-up blood/urine tests help your vet spot changes early and adjust the plan before a crisis develops.

What This Means for You and Your Dog

A diagnosis of chronic kidney disease can feel overwhelming—but it does not mean your dog can’t still have good days, joy, and comfort.

You can help by:

  • Following your vet’s diet and medication recommendations
  • Encouraging drinking (fresh water, and sometimes broths approved by your vet)
  • Watching for changes in appetite, energy, vomiting, or bathroom habits
  • Keeping follow-up appointments and lab checks
  • Talking openly with your veterinary team about your goals and concerns

With early detection, thoughtful management, and a focus on quality of life, many dogs with kidney disease live happily for months or years after diagnosis.

Supporting You Through a Kidney Disease Diagnosis

Facing kidney disease in your dog can bring up a lot of emotions—worry, sadness, confusion, and love all at once. You don’t have to navigate it alone.

By understanding the 4 stages of kidney disease in dogs and working closely with your veterinarian, you can make informed, compassionate decisions that honor both your dog’s life and their comfort.