Quick Answer: The earliest signs of kidney disease in cats are increased thirst, more frequent urination, and subtle weight loss. These changes happen because the kidneys have already lost a significant portion of their function by the time they become noticeable, which is why regular bloodwork in senior cats matters more than watching for symptoms alone. Later signs include a dull coat, decreased appetite, occasional vomiting, and lethargy.
Noticed one of these signs in your own cat? You don’t have to figure this out alone. The Feline Kidney Message Board is a free community of other caregivers going through the same thing.
Why Early Signs Are So Easy to Miss
Cats are built to hide illness, and kidney disease is a slow, quiet process on top of that. In the early stages, a cat’s body compensates for the loss of kidney function well enough that most cats show no obvious signs at all. By the time a cat starts acting sick in a way an owner clearly notices, a large share of kidney function is often already gone.
That combination, a slow disease and an animal that hides discomfort well, is why so many cats are diagnosed later than caregivers would like. It is also why the changes worth watching for are subtle ones, not dramatic ones.
The Earliest Symptoms to Watch For
Drinking more water than usual. As kidneys lose the ability to concentrate urine, cats need to drink more to make up for the fluid they are losing. This is often the very first thing an owner notices, sometimes before anything else changes.
Urinating more, and larger volumes. This goes hand in hand with increased thirst. Litter box clumps may look noticeably larger, or you may find yourself scooping more often.
Subtle weight loss. A cat that looks the same day to day can still be quietly losing weight over weeks or months. Weighing your cat at home on a kitchen scale every few weeks, or checking their weight at each vet visit, catches this far more reliably than eyeballing it.
A slightly reduced appetite. Not refusing food outright, just eating a bit less enthusiastically or leaving food behind that they used to finish.
A duller coat. Cats with declining kidney function often groom less effectively, and the coat can start to look less sleek than usual.
Any one of these alone could mean nothing. Together, or in an older cat, they are worth a vet visit and bloodwork.
Symptoms That Show Up as Disease Progresses
As kidney function declines further and waste products build up in the bloodstream, symptoms tend to become harder to miss:
- Vomiting, which may start out occasional and become more frequent
- Lethargy and general malaise
- Noticeable weight loss and muscle loss
- Oral ulcers or discomfort while eating, related to elevated urea levels
- A chemical or ammonia-like smell to the breath
- Pale or white gums, which can point to the anemia that often develops alongside CKD
- Poor coat quality that is now obvious rather than subtle
These later signs are the ones most caregivers associate with kidney disease, but by the time they appear, the disease has usually progressed well past the early stage.
Why Bloodwork Catches This Before Symptoms Do
Standard kidney bloodwork looks at creatinine, BUN, and increasingly SDMA, along with a urinalysis to check how concentrated the urine is. SDMA in particular can rise before creatinine does, which means it sometimes flags reduced kidney function earlier than older testing methods could.
Even with these tools, a meaningful portion of kidney function is typically gone before any test reliably detects a problem. That is not a failure of the testing, it is simply how much reserve capacity the kidneys have. It is also the core reason vets recommend routine bloodwork for senior cats on a regular schedule, rather than waiting for symptoms to prompt a vet visit.
If you are looking to understand what a specific creatinine or BUN number on your cat’s results actually means, that is covered in our diagnosis and labs page. Or, post on our community forum, the Feline Kidney Message Board (FKMB).
When to Call Your Vet
Any combination of increased thirst, increased urination, or unexplained weight loss in a cat, especially one over seven years old, is worth a vet visit and bloodwork. You do not need to wait for your cat to seem obviously unwell. Given how much kidney function is typically already lost by the time symptoms are noticeable, earlier testing gives your cat, and you, more room to catch this early and start managing it.
FAQ
Can a cat have kidney disease with no symptoms at all? Yes. In the early stages, cats often show no obvious clinical signs because their body compensates for the reduced kidney function. This is why routine bloodwork matters more than watching for symptoms in senior cats.
How old does a cat typically need to be before kidney disease becomes a concern? Kidney disease becomes more common as cats age, particularly past seven to ten years old, though it can occur in younger cats too, especially after an acute kidney injury.
Is increased thirst always a sign of kidney disease? Not always. Increased thirst and urination can also point to diabetes or hyperthyroidism, both of which are also more common in older cats. This is exactly why bloodwork, not guessing based on symptoms alone, is the right next step.
My cat’s coat looks duller lately. Should I be worried? On its own, not necessarily, coats can change for many reasons. But paired with increased thirst, weight loss, or reduced appetite, it is worth mentioning to your vet.
Sources
Cornell University College of Veterinary Medicine, Feline Health Center, Chronic Kidney Disease Morris Animal Foundation, Chronic Kidney Disease in Cats, Symptoms, Diagnosis, and Treatment PetMD, Kidney Disease in Cats, Signs, Causes, and Treatment