What I'm Actually Looking For in a Senior Pet's Bloodwork
Bloodwork on an older pet isn't an upsell. It's how I catch the silent stuff (kidney, liver, thyroid, diabetes, anemia) months before your pet looks sick, while we still have options. Pets hide illness. Numbers don't.
Written by Dr. Steve Pelton, DVM · 26 years in practice
The honest version
When a 12-year-old comes in for a senior checkup, the exam tells me a lot. But a lot of the most important diseases in older pets don't show up under my hands or in the room. They show up in the numbers first. That's what the blood draw is for.
Here's the part the chains won't always say plainly: senior bloodwork is not a way to pad the bill. It's the single best tool I have for finding kidney disease, liver trouble, thyroid problems, and diabetes while they're still small. By the time your pet looks sick, the disease has usually had a head start. I'd much rather find it while your dog or cat is still bouncing around the house, because that's when I have real options.
A senior dog is around 7 to 8 years old, and cats are about the same. Big-breed dogs get there a little sooner. The exact age matters less than the idea: once a pet is older, I want a baseline I can compare against year to year, every year.
Pets hide illness. That's the whole problem.
Dogs and cats are wired to act normal even when they feel awful. It's survival instinct. A cat with early kidney disease will eat, purr, and curl up in the sun like nothing's wrong, sometimes for a long time. You won't see it. I won't always see it on exam either. But the blood and urine will start to whisper before your pet ever shows you a thing.
I've caught thyroid problems, kidney disease, and liver issues this way, often while the pet still looked perfectly fine. The one that really drives it home is splenic tumors. A dog comes in looking okay, the bloodwork shows a low hematocrit, we take X-rays, and there's a tumor on the spleen we would never have found until it ruptured. I've seen that play out more than a few times, and catching it early is the whole ballgame.
What each value tells me
I don't run a panel to drown you in numbers. I run it to answer a short list of questions. Think of it the way I think about an itchy dog: it usually comes down to fleas, food, or atopy. Senior bloodwork has its own short list. Here's what I'm reading.
Reading the panel
Value → what it tells me
Kidney values: BUN, creatinine, SDMA
These tell me how the kidneys are holding up. SDMA is the one I lean on, because it tends to rise earlier than the older values, so it can catch kidney decline sooner. Early kidney disease is common in older pets, cats especially.
Liver enzymes: ALT, ALP
When these climb, the liver is under stress or there's disease brewing. They don't tell me the whole story by themselves, but they tell me where to look next.
Thyroid: T4
In older cats I'm watching for an overactive thyroid, which is one of the most common quiet problems in senior cats. In some dogs it's the opposite, an underactive thyroid. Either way, T4 is how I start that conversation.
Blood glucose
High blood sugar points me toward diabetes. Caught early, that's a manageable disease. Caught late, it's a crisis. The number is how I tell which way we're heading.
CBC: red and white cells
The red cells flag anemia, which is often a clue to something bigger going on. The white cells hint at infection or inflammation. Together they're a quick read on whether the body is fighting something.
Urine: USG and urinalysis
I almost always want a urine sample with the blood. It shows me how well the kidneys are concentrating, catches infection, and can surface diabetes markers. Blood and urine together tell me far more than either one alone.
Why I look at trends, not just one report
A single panel is a snapshot. The real power comes from comparing this year to last year. A value that's still inside the normal range but drifting in the wrong direction can be the earliest warning I get. That's why I push for a baseline while your pet is healthy, so the numbers mean something later.
Senior bloodwork pairs naturally with the rest of the senior plan. It's part of our senior wellness care and fits inside our wellness panels, and the results often shape what I recommend for weight and nutrition, because diet does real work in managing kidney, thyroid, and blood-sugar issues once we know what we're dealing with.
None of this is about fear. It's about staying ahead. The pets who do best in their senior years are usually the ones whose owners let me peek at the numbers before anything looks wrong.
Common questions
Senior bloodwork, answered straight
Does my senior dog really need bloodwork?
Most of the time, yes. By the time a senior pet acts sick, the disease has usually been brewing for a while. Bloodwork lets me see kidney, liver, thyroid, and blood-sugar trends before your dog looks off, which is exactly when we still have good options. It isn't an upsell. It's how I catch the quiet stuff early.
What does senior bloodwork actually check for?
The big ones: kidney function (BUN, creatinine, and SDMA), liver enzymes (ALT, ALP), thyroid (T4), blood glucose for diabetes, and a CBC that flags anemia or signs of infection and inflammation. I pair it with a urine sample to see how well the kidneys are concentrating and to catch infection or diabetes markers. Each value tells me something different.
What is SDMA?
SDMA is a kidney marker that tends to rise earlier than the older values like BUN and creatinine. The older numbers often don't move until a good chunk of kidney function is already gone. SDMA can flag decline sooner, which matters a lot in older cats especially, because earlier means more options.
How often should an older pet get bloodwork?
I recommend it once a year for senior pets. That gives me a fresh baseline and lets me compare numbers year over year, which tells me far more than any single snapshot.
My pet seems fine. Why test?
Because pets hide illness. It's instinct. A dog or cat can feel rotten and still wag, purr, and eat. Numbers don't pretend. Bloodwork on a pet that looks fine is the whole point: we find the problem while it's small and manageable instead of after it's an emergency.
What's in your senior panel and what does it cost?
Our senior panel is $285, and you can see exactly what's included on our wellness panels page. I'll always tell you the price up front and what each part is for before we run anything. No surprises. If you want to see how I think about pricing in general, read why my exam costs what it costs.
What if the bloodwork comes back normal?
Then that's a win, and it isn't wasted money. A normal panel becomes your pet's baseline. Next year, when I run it again, I'm comparing against your pet's own healthy numbers instead of a generic range. A value that's still technically normal but drifting from last year can be the first hint something's starting.
Does my senior cat need bloodwork too?
Especially cats. Older cats are the classic case for two silent problems: early kidney disease and an overactive thyroid. Both can run quietly for a long time. Cats are also masters at hiding how they feel, so the bloodwork often knows before you do.
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If your pet is 7 or older, let's get a baseline
The best time to run senior bloodwork is before anything looks wrong. Let's check the numbers while your pet is still feeling good, so we catch the quiet stuff early.