Kidney Disease in Cats
Kidney disease is the most common serious condition in older cats — and one of the most manageable when caught early. The problem is that cats rarely show obvious symptoms until they've already lost significant kidney function.
This guide covers what chronic kidney disease (CKD) actually is, the early signs most owners miss, how it's diagnosed and staged, and what management looks like in practice — so you know what you're dealing with and what to ask your vet.
What it is
What chronic kidney disease actually means.
The kidneys filter waste from the blood, regulate hydration, control blood pressure, and produce hormones that support red blood cell production. In CKD, the functional tissue of the kidneys is gradually replaced by scar tissue — a process that is irreversible but manageable.
Because kidneys have enormous reserve capacity, cats can lose up to 75% of kidney function before bloodwork shows significant abnormalities. By the time a routine blood panel flags CKD, the disease is often already well established.
Prevalence: Studies estimate that 30–40% of cats over 10 years old have some degree of chronic kidney disease. It is the leading cause of death in older cats.
Early signs
What to watch for before bloodwork shows it.
These signs are easy to attribute to normal aging — and that's exactly why they get missed. Any one of them in a cat over 7 is worth investigating.
1
Increased thirst and urination
Often the first noticeable sign. As the kidneys lose concentrating ability, cats produce more dilute urine and compensate by drinking more. Many owners don't notice until the litter box is unusually wet or the water bowl empties faster than usual.
2
Weight loss and muscle wasting
Gradual weight loss, particularly loss of muscle along the spine and hindquarters. This happens even when appetite appears normal, because failing kidneys disrupt protein metabolism.
3
Reduced appetite and nausea
Toxin buildup in the blood causes nausea and reduced appetite. Cats may appear interested in food but walk away after a sniff, or start leaving food they previously finished.
4
Lethargy and reduced activity
A cat sleeping more or engaging less is easy to attribute to age. In the context of CKD, it reflects the body working harder to compensate for reduced kidney function.
5
Poor coat quality
A dull, unkempt, or greasy coat — especially in a cat that was previously fastidious about grooming — often reflects systemic illness, including early kidney disease.
6
Bad breath with a chemical or ammonia odor
Uremic breath — a smell sometimes described as ammonia or nail polish remover — is a sign that waste products are building up in the bloodstream. This typically appears in more advanced disease.
Diagnosis and staging
How CKD is diagnosed and what the stages mean.
Diagnosis involves bloodwork (creatinine, BUN, phosphorus, SDMA) and urinalysis. The IRIS (International Renal Interest Society) staging system — Stages 1 through 4 — guides treatment decisions based on how much kidney function remains.
1
Early
Kidney damage present but bloodwork near normal. Best time to intervene. Often detected only via SDMA testing.
2
Mild
Mildly elevated creatinine. Subtle signs may begin. Dietary management and monitoring typically begin here.
3
Moderate
Moderate elevation. More obvious clinical signs. Active management required — diet, hydration, blood pressure, phosphorus control.
4
Severe
End-stage. Significant toxin buildup. Focus shifts to comfort care and quality of life management.
Saving Grace tip: SDMA — a newer kidney biomarker — can detect CKD up to 17 months earlier than creatinine alone. Ask your vet to include SDMA in annual bloodwork for any cat over 7.
Management
CKD is not curable — but it is manageable.
The goal of management is slowing progression, maintaining quality of life, and keeping your cat feeling as well as possible for as long as possible. Most cats with early-to-mid stage CKD can live comfortably for years with appropriate care.
Renal diet
Prescription kidney diets are lower in phosphorus and protein — both of which place extra load on diseased kidneys. This single intervention has the strongest evidence for slowing CKD progression.
Hydration support
Wet food, water fountains, and in moderate-to-advanced disease, subcutaneous fluids administered at home — often one of the most impactful interventions for maintaining quality of life.
Blood pressure management
Hypertension is common in CKD cats and accelerates kidney damage. Medication is often required and is highly effective at slowing progression when introduced at the right stage.
Regular monitoring
Bloodwork and urinalysis every 3–6 months depending on stage. Catching progression early allows treatment adjustments before symptoms worsen. Consistency matters more than any single value.
Concerned about your cat's kidney health?
Saving Grace offers in-home wellness visits including bloodwork and urinalysis across greater Los Angeles. For cats who find clinic visits stressful — which is most of them — being assessed at home produces more accurate results and a calmer experience.
