Kidney failure is the phrase people hear after a cat starts drinking more, weeing larger clumps, losing weight, or going off food — and suddenly every quiet change feels urgent. Some causes are slow and age-linked. Others are sudden and time-critical, like toxin exposure, where waiting for symptoms can cost kidney function.
Below is a clear guide to what kidney failure in cats can look like, what usually causes it, how vets confirm it, and what day-to-day care tends to involve once a diagnosis is made. The aim is simple: recognise the patterns early, avoid common traps, and know when it’s an emergency.4, 5, 6
What “kidney failure” means in cats
Vets generally use “kidney failure” to describe kidneys that can no longer do their main jobs well enough: filtering waste products, balancing water and salts, and helping regulate blood pressure. In cats, this tends to show up in two broad ways:
- Chronic kidney disease (CKD): a gradual, usually irreversible decline over months to years, most common in older cats.
- Acute kidney injury (AKI): a sudden loss of kidney function (over hours to days), sometimes reversible if treated fast — often linked to toxins, severe dehydration, or serious infection/obstruction.
These two can blur. A cat with CKD can have an acute “crash” on top of it, and the signs may look similar at home.5, 6
Causes of kidney failure in cats
Chronic kidney disease (slow-burn causes)
In many cats, the exact trigger for CKD is never pinned to one single cause. What’s often seen is gradual loss of functional kidney tissue over time. Age matters, and so do conditions that quietly strain the kidneys over years.6
Acute kidney injury (sudden causes that need urgent care)
AKI can be triggered by a short, sharp event — and this is where speed changes outcomes. Important examples include:
- Toxins: exposure to true lilies (Lilium and Hemerocallis species) is a well-recognised emergency in cats and can cause severe, sometimes fatal kidney injury. Even small exposures (including pollen or vase water) can be dangerous.2, 3
- Severe dehydration or shock reducing blood flow to the kidneys.
- Urinary blockage (more common in male cats) leading to back-pressure and rapid illness.
If you suspect a toxin exposure (especially lilies), don’t wait for signs. Ring your vet or an animal poisons service straight away.2, 3
Breed, age, and genetics
CKD is particularly common in older cats, partly because kidney changes accumulate quietly. Some inherited or breed-associated kidney conditions exist, but for most household cats, age and individual history outweigh breed alone.6
Symptoms of kidney failure in cats
Early signs people notice at home
Early kidney disease can be subtle. Often it looks like “just ageing” until the pattern becomes hard to ignore. Common early signs include:
- Drinking more water than usual
- Urinating more (bigger litter clumps, more frequent trips)
- Weight loss and reduced muscle
- Reduced appetite or fussier eating
- Dull coat, dehydration, or bad breath
None of these signs are exclusive to kidney disease, which is why testing matters — but they’re enough to justify a vet visit.6
As kidney failure progresses
As waste products build up and hydration becomes harder to maintain, signs can become more obvious:
- Vomiting and/or diarrhoea
- Lethargy, weakness, hiding more
- Mouth ulcers or worsening breath
- Pale gums (anaemia)
- In severe cases: stumbling, seizures, or marked confusion
Advanced signs are a signal to seek veterinary care promptly, even if the cat has “good moments” between episodes.6
Diagnosis and testing
Kidney disease is diagnosed by combining history, physical exam findings, and lab testing — because no single number tells the whole story. Common components include:
- Blood tests to assess waste products and electrolytes (including creatinine and urea).
- SDMA, a blood marker that can help detect reduced kidney function earlier in some cats and is used alongside creatinine in staging guidance.1, 7
- Urinalysis to check urine concentration and look for evidence of protein loss or infection.
- Blood pressure measurement, because hypertension can be both a consequence of CKD and a driver of further damage.7
- Imaging (ultrasound and/or X-rays) to assess kidney structure and rule out obstruction or other disease.
Staging matters because treatment priorities change by stage. The widely used IRIS approach stages CKD using creatinine (with SDMA as support), then “sub-stages” based on protein in the urine and blood pressure.7
Treatment options for kidney failure in cats
The main goals
Treatment usually aims to slow progression where possible, reduce nausea and dehydration, manage blood pressure and protein loss, and keep the cat eating. Plans are adjusted over time as the disease shifts.6
Diet: one of the biggest levers for CKD
For cats with CKD, therapeutic renal diets are typically formulated to restrict phosphorus and provide modest amounts of high-quality protein. Evidence-based veterinary guidance notes improved outcomes for cats with CKD fed renal diets, and these diets are commonly recommended from IRIS stage 2 onwards (your vet will match this to the full clinical picture).6
Food acceptance matters. A renal diet that’s eaten reliably is more useful than a “perfect” diet that sits untouched. If appetite is low, your vet may recommend gradual transitions, warming food, trying different textures, or medical support for nausea and appetite.6
Medications and supportive care (common categories)
- Anti-nausea and appetite support when eating becomes difficult.6
- Blood pressure control if hypertension is present.7
- Proteinuria management if urine protein loss is contributing risk.7
- Phosphate binders may be added if blood phosphorus remains high despite diet changes.6
- Fluid therapy (IV in hospital for acute crises; sometimes guided subcutaneous fluids at home for selected CKD cats).
Medication choices vary by country, stage, and the cat’s other conditions, so the safest plan is the one built from that cat’s bloodwork, urine results, blood pressure, and body condition over time.6, 7
Managing chronic kidney disease day to day
Living with CKD often looks ordinary from the outside: a cat in a warm patch of light, choosing short bursts of movement, eating in small sessions. Management is mostly quiet repetition.
- Hydration: offer multiple water stations; consider a fountain; favour wet food where appropriate.
- Regular monitoring: rechecks help track trends (weight, muscle, blood pressure, urine concentration, creatinine/SDMA, phosphorus), not just single results.7
- Watch the small signals: appetite, litter habits, vomiting frequency, and how quickly the cat recovers after activity.
Prevention and early intervention
What you can do that genuinely helps
- Reduce toxin risk at home: avoid bringing true lilies into a cat household, and check plants before they come through the door.2, 3
- Book check-ups for older cats and ask what screening is sensible for their age and history, particularly if thirst/urination patterns change.
- Act early on appetite change (especially if paired with weight loss or increased drinking), because cats can decline quickly once they stop eating well.
Quality of life and end-of-life care
Many cats with CKD still have long stretches of comfort. The aim is not perfection, but steadiness: good days that outweigh the hard ones, and a plan for when the balance changes.
Consider a conversation about palliative care if you’re seeing persistent vomiting, refusal of food despite support, severe weight loss, repeated dehydration crises, or signs of distress that don’t settle with treatment. Your vet can help you assess pain, nausea, hydration, and day-to-day function in a clear, compassionate way.6
Is kidney failure in cats always fatal?
Kidney disease is serious, but many cats with CKD live for months to years with careful management. Acute kidney injury can sometimes be reversible if the cause is identified and treated early, especially with prompt fluid therapy and monitoring.6
What are the first signs of kidney disease in cats?
Common early signs include increased thirst and urination, gradual weight loss, and a drop in appetite. Because these signs overlap with other illnesses, confirmation relies on blood and urine testing.6
What should I do if my cat has been near lilies?
Treat it as an emergency. Remove access and contact a vet immediately — true lilies (Lilium and Hemerocallis) can cause severe kidney injury in cats, and early treatment offers the best chance of survival.2, 3
Why do vets measure SDMA as well as creatinine?
SDMA is used alongside creatinine because it can help identify reduced kidney function earlier in some cats, and it’s included in guidance used for CKD staging and interpretation.1, 7
References
- IDEXX Laboratories — SDMA added to IRIS CKD staging guidelines (announcement and context)
- RSPCA NSW — Toxic plants (cats and lilies)
- Lort Smith Animal Hospital — Lilies toxicity information (includes feline kidney injury emergency guidance)
- Animal Poisons Helpline (Australia) — Pet poison advice service
- Veterinary Ireland Journal — Chronic kidney disease in cats (overview; IRIS staging concepts)
- Merck Veterinary Manual — Renal dysfunction in dogs and cats (nutrition and management)
- Toray Animal Health — Diagnosing feline CKD (IRIS staging; substaging by proteinuria and blood pressure)
- Journal of Veterinary Internal Medicine (PubMed) — Study referencing IRIS stages 1–4 CKD in cats
Veterinary Advisor, Veterinarian London Area, United Kingdom