Why Your Cat’s Annual Bloodwork Catches What a Healthy Exam Can Miss
By Dan Gray, DVM | Gentle Vet, Green Bay, WI
An eight-year-old neutered male came in for his annual visit this spring — bright eyes, good appetite, no limp, no fuss in the carrier. By every outward sign, a completely normal cat. His owner almost skipped the bloodwork that year to save herself a trip. However after a bit of discussion she agreed to our annual wellness panel.
The CBC and chemistry came back unremarkable. The urinalysis didn’t. There was more blood sitting in the urine sediment than stress would explain — not the kind of thing you’d ever catch by watching a cat walk across a room. That single result sent us down a path of imaging that found an early bladder stone, still small enough to dissolve with a prescription diet rather than remove surgically. No symptoms. No litter box accidents. No limping. Just a test result that saw something the exam couldn’t.
Most importantly, since this cat was male, we potentially avoided a life-threatening, painful, and expensive urinary blockage!
That’s the case for routine bloodwork in cats generally. Cats are remarkably good at acting fine even when they’re not, and a basic blood and urine panel is often the only thing standing between a quiet problem and an expensive, painful or life threatening one. Below is what your cat’s panel actually checks, why we start watching it closely starting around age eight to ten, and why one good result doesn’t guarantee the next one will look the same.
Cats Are Built to Hide Being Sick
Cats evolved as both predator and prey — hunters of smaller animals, and prey to larger ones. That second role wired something permanent into their behavior: showing weakness invites a threat, so the instinct to mask pain and illness runs deep, even in a cat who’s never seen anything wilder than the back porch. Veterinary writers covering feline behavior have described this as cats being remarkably skilled at hiding pain to protect themselves — a survival habit that doesn’t turn off just because the cat in question sleeps on a heated bed and eats from a ceramic bowl (AAHA).
That instinct makes early disease nearly impossible to catch through observation alone. By the time an owner notices something real — less water in the bowl at the end of the day, less interest in food, a bit less energy on the stairs — the underlying problem has often been building for months. Routine bloodwork sidesteps that limitation. It screens for organ function and disease markers that a cat can’t communicate, and a physical exam can’t always reveal.
What’s Actually Being Measured in a Routine Panel
At Gentle Vet, a standard senior screening includes four pieces, each looking at a different system. None of them is optional padding — each one catches something the others can’t.
Complete Blood Count (CBC)
The CBC counts red blood cells, white blood cells, and platelets. A drop in red cells points toward anemia; a rise in white cells often signals infection or inflammation, though a gradual drift in white cells over a few years — even while staying inside the normal range — is one of the patterns we watch for, since it can be an early flag for chronic disease developing quietly in the background. Platelet counts matter too: too few raises bleeding risk, too many can raise the risk of clotting problems.
Full Chemistry Panel
The chemistry panel measures kidney values (creatinine, BUN), liver enzymes, blood glucose, electrolytes, and total protein. This is where early kidney disease most often shows up first, sometimes alongside a kidney-specific marker called SDMA, which we’ll come back to below. Trends in liver enzymes or glucose here can also flag problems — like early diabetes — well before a cat shows obvious symptoms. Our team reviews every value against both the standard reference range and your cat’s own history.
Thyroid Testing (T4)
Hyperthyroidism is one of the most common hormonal diseases in older cats, and it tends to develop gradually — a slow climb in T4 over a couple of years, often well before a cat shows the classic signs of weight loss despite a good appetite. Watching T4 trend upward, even while each individual result is still technically “normal,” is one of the more reliable early warnings we have for this disease.
Urinalysis and Urine Culture
The urine sample checks concentrating ability, protein levels, blood, crystals, and bacteria, and our in-house urine culture identifies infections precisely enough to choose the right antibiotic the first time. It’s also, as in the case above, where stones, early infections, and subtle kidney changes often show up first — frequently before anything else on the panel does.
Catching Kidney Disease Before It’s “Kidney Disease”
If there’s one area where annual bloodwork earns its cost most clearly, it’s chronic kidney disease. Cats are prone to it as they age, and by the time the traditional marker — creatinine — climbs above normal, a meaningful share of kidney function is often already gone.
SDMA, a newer kidney marker, tends to rise earlier. In one published feline study tracking cats that went on to develop chronic kidney disease, SDMA climbed above the normal range an average of 17 months before creatinine did — in some cats, more than a year and a half earlier (Today’s Veterinary Practice). Paired with urine protein levels from the urinalysis, SDMA gives us a meaningfully earlier window to start managing kidney health through diet and monitoring, rather than reacting once a cat is already feeling the effects.
None of this requires a sick cat or an owner who suspects something is wrong. It just requires showing up for the annual draw.
Why One Snapshot Isn’t Enough — It’s the Trend That Talks
A single “normal” result is reassuring, but it’s the comparison across years that does the real diagnostic work. A white cell count that’s technically within range but has been quietly dropping for three years tells a different story than the same number appearing for the first time. The same goes for a platelet count drifting downward, or a thyroid value creeping up year over year. None of these would trigger a flag on a single report — but lined up side by side, they often tell us exactly where to look next (AAHA).
This is also why we don’t love skipping a year just because a cat seems fine. A skipped year isn’t just a missed test — it’s a gap in the trend line that makes the next abnormal result harder to interpret with confidence.
When We Start Recommending Annual Bloodwork
The 2021 AAHA/AAFP Feline Life Stage Guidelines recommend that mature adult cats, ages seven to ten, have baseline screening roughly every one to two years, increasing to at least yearly — with every six months suggested — once a cat reaches senior status past age ten (AAHA/AAFP Feline Life Stage Guidelines). At Gentle Vet, we start the conversation a little earlier than the guideline minimum: we recommend annual bloodwork beginning around age eight to ten, specifically because kidney and thyroid disease both tend to begin their slow climb in this window, long before a cat reaches the formal “senior” label.
If a screening turns up something worth tracking — an early kidney trend, a thyroid value on the move — we’ll usually shift to rechecking every three to six months until things stabilize. Earlier screening is always welcome if you’d like the baseline sooner, and it’s something worth raising at any wellness visit, regardless of your cat’s age.
Two Small Things That Help Between Visits
Fasting requirements depend on which parts of the panel we’re running, so if possible try avoiding food being provided to your pet 8-12 hours prior to a blood test.
The other thing worth mentioning, even if it feels too minor to bring up: any small shift in water intake, litter box habits, or appetite. These are exactly the kinds of details that connect to a trend on paper, and you’re the only one who'd notice them happening at home.
Frequently Asked Questions: Cat Bloodwork and Early Detection
What’s included in my cat’s annual bloodwork at Gentle Vet?
Our standard senior screening includes a complete blood count (CBC), a full chemistry panel, T4 thyroid testing, a urinalysis, and an in-house urine culture. Together, these check organ function, blood cell health, thyroid activity, and urinary tract health in a single visit.
My cat seems perfectly healthy. Why does she need this test every year?
Cats hide illness well, even from people who know them best. Bloodwork can pick up early changes in kidney function, thyroid activity, or blood cell counts long before any outward symptoms appear — and a normal year is itself useful information, since it gives us a true baseline to compare against later.
What is SDMA, and why do you test for it?
SDMA (symmetric dimethylarginine) is a kidney marker that often rises before the traditional marker, creatinine, climbs out of the normal range. In published research, SDMA increased an average of 17 months before creatinine in cats that went on to develop chronic kidney disease, giving us a meaningfully earlier opportunity to start management with diet and monitoring.
Does my cat need to fast before bloodwork?
It depends on which tests are being run but as a general rule if you can, please have your cat fasted for 8-12 hours.
What happens if something on the panel looks abnormal?
Most abnormal results don’t mean an emergency — they mean a conversation. We’ll walk through what we’re seeing, whether repeat testing or imaging makes sense, and what monitoring or treatment plan fits your cat and your household.
The Bloodwork Appointment That Might Catch the Thing You’d Never Guess
If it’s been a year or more since your cat’s last bloodwork — or your cat just turned eight and you haven’t started yet — now’s a good time to get on the schedule. It’s a short blood draw and a urine sample that can save months of guessing later, and it’s one of the simplest things you can do for a cat who’d never tell you something was wrong in the first place.
Gentle Vet Animal Hospital
2560 University Ave, Green Bay, WI
(920) 435-5000
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