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Senior Dog Bloodwork: What Each Test Catches, and How to Read the Results

Senior Dog Bloodwork: What Each Test Catches, and How to Read the Results

By Sarah Bennett · Last updated July 22, 2026 · 10 min read

I write as a researcher and owner, not a veterinarian. Bloodwork is read in the context of your dog, her history, and her exam, which is your vet's job. This guide helps you understand the panel and ask better questions, not diagnose from a printout.

The short version: Senior dog bloodwork is the single most useful early-warning tool you have, because it catches kidney disease, thyroid problems, diabetes, and liver changes months to years before you would notice anything at home. A standard senior panel is really four tests doing different jobs: a CBC (blood cells), a chemistry panel (organs), a thyroid test (T4), and a urinalysis (kidney concentrating ability). Two things most owners are never told: the urine test often flags kidney trouble before the blood does, and a single normal result matters less than the trend across visits, which is why building a baseline while your dog is well is worth so much. Ask whether SDMA, an early kidney marker, is included.

What Senior Dog Bloodwork Actually Tests

When your vet says "let's run senior bloodwork," they usually mean a bundle of tests, each watching a different system. Knowing what each one does turns a scary printout into something you can follow.

Complete Blood Count (CBC): the blood cells. The CBC counts red cells, white cells, and platelets. It catches anemia (low red cells, which can point to chronic disease, bleeding, or kidney disease), signs of infection or inflammation (white cell changes), and clotting problems (platelets). It tells you nothing about organ function, that is the next test's job.

Chemistry panel: the organs. This is the workhorse. A comprehensive chemistry panel measures kidney values (BUN, creatinine), liver enzymes (ALT, ALP), blood sugar (glucose), protein, and electrolytes. It is where early kidney disease, liver changes, and diabetes first show up in the blood.

SDMA: the early kidney marker worth asking for. SDMA is a newer kidney test, and it matters for seniors specifically. IDEXX, which developed the test, puts the gap like this: "Creatinine cannot identify kidney issues until almost 75% of kidney function is lost", while "SDMA increases when there is, on average, a 40% decrease in GFR". In a 2016 study of 19 dogs with naturally occurring chronic kidney disease, SDMA rose before creatinine in 17 of them, by a mean of 9.8 months and in one dog by more than two years. It also is not thrown off by low muscle mass, which is common in older dogs and can make creatinine misleadingly low. If your senior panel does not include SDMA, it is worth asking for.

Thyroid test (Total T4): the metabolism. Hypothyroidism is common in middle-aged and older dogs, and its signs (weight gain, low energy, coat changes, recurrent skin or ear infections) are easy to write off as "just aging." A T4 screens for it, and a full thyroid panel confirms. Our guide to hypothyroidism in senior dogs covers what a low result means.

Urinalysis: the test that often catches kidney disease first. This is the one owners most often skip, and it is a mistake. A urinalysis measures urine specific gravity, how well the kidneys are concentrating urine, and that ability drops before kidney values change in the blood. Failing kidneys lose the ability to concentrate urine early, so dilute urine can be the first hard sign of trouble. A urinalysis also catches urinary infections, protein loss, and diabetes (sugar in the urine). Blood and urine together see far more than blood alone.

What Those Codes on the Lab Slip Mean (Chem 24, CBC, T4, SDMA, HW/Tick)

The estimate a clinic hands you rarely spells any of this out. It lists panel names and abbreviations, and those names come from whichever laboratory the practice sends its samples to, so the same dog can get two differently worded invoices at two clinics for nearly identical testing.

What the slip says What it stands for What it is looking at
CBC Complete blood count Red cells, white cells, and platelets: anemia, infection, inflammation, clotting
Chem, Chem 10, Chem 17, Chem 24 Chemistry panel Organ function and electrolytes. The number is how many individual values the panel runs, not a grade of quality
T4 or TT4 Total thyroxine Thyroid function
SDMA Symmetric dimethylarginine Kidney function, and it moves earlier than creatinine
UA or Urine Urinalysis Concentrating ability, protein, infection, crystals
HW Heartworm Heartworm antigen, usually from the same blood draw
Tick Dz, 4Dx Tick-borne disease screen Exposure to Lyme, Ehrlichia, Anaplasma and similar, depending on the panel
KeyScreen KeyScreen GI Parasite PCR A stool test, not a blood test

Two things are worth knowing about the numbered panels. The number tells you how many separate values get measured, so a Chem 24 runs more individual tests than a Chem 10, but it says nothing about which ones, and panels sold under similar names can contain different values. If the difference matters to you, ask the clinic to print the itemized list rather than the panel name. Most practice software can do it while you wait.

The stool test is the one that surprises people on a bloodwork invoice. KeyScreen is a fecal PCR panel from Antech, and its product page states that "KeyScreen detects 20 intestinal parasites, benzimidazole resistance in hookworms, and determines the zoonotic potential of Giardia." For an older dog the resistance finding is the useful one, because a hookworm that shrugs off the usual dewormer is worth knowing about before you treat rather than after it fails.

How to Read Senior Dog Blood Test Results

You do not need to interpret the numbers yourself, that is your vet's job, but understanding the logic helps you ask the right questions.

  • In range vs out of range. Results are compared to a reference range printed beside each value. A value flagged high or low is a starting point for a conversation, not a diagnosis on its own.
  • The trend matters more than any single result. This is the part most owners are never told. A value sitting at the high end of normal is not alarming by itself, but if it has climbed steadily across the last three visits, that trajectory can reveal a developing problem while it is still early. A single panel is a snapshot; a series of panels is a story. This is the real reason to build a baseline while your dog is healthy: it gives every later result something to be compared against.
  • One odd value is rarely the whole picture. Vets read the panel as a pattern. A mildly elevated liver enzyme with everything else normal means something different from the same value alongside changes in kidney and protein. Resist the urge to diagnose from one flagged line.

Why Senior Bloodwork Catches So Much

The reason bloodwork earns its place is simple: dogs hide illness, and their bodies compensate for a long time. A dog can lose a large share of kidney function, or run an underactive thyroid for months, while looking and acting essentially normal at home. Bloodwork sees the change underneath before the dog shows it. The four conditions most often caught early this way, kidney disease, thyroid dysfunction, diabetes, and liver changes, are all far more manageable when found early than when found after symptoms appear. The same panel earns its keep before a procedure, too: a pre-anesthetic blood test screens organ function so your vet can plan safe anesthesia for a senior dog.

How Often Should a Senior Dog Have Bloodwork?

Frequency scales with age and health, rather than being one-size-fits-all.

  • Around ages 7 to 10 (healthy): most vets recommend a wellness exam and a blood panel once a year, establishing the baseline the later years will be measured against.
  • Over about age 10, or any dog with a chronic condition: the recommendation usually shifts to twice a year. Semi-annual testing catches a developing problem earlier than annual testing does, simply because there are more chances to see a trend turn.
  • Dogs already managing a disease (kidney disease, diabetes, Cushing's) often need bloodwork every 3 to 4 months to track the condition and adjust treatment, on a schedule your vet sets.

The through-line: the older or sicker the dog, the more value there is in checking more often, because early detection depends on catching a trend before it becomes a crisis.

What Does Senior Dog Bloodwork Cost?

Pricing varies widely by region, clinic, and how comprehensive the panel is, so treat any number as a ballpark and check with your clinic. A basic senior wellness panel (CBC plus chemistry) is typically a moderate add-on to the exam fee; adding a urinalysis, SDMA, thyroid testing, or blood pressure raises it. It is worth asking your vet for an itemized estimate, and asking which tests they consider essential versus optional for your particular dog. Set against the cost of treating a disease caught late, a wellness panel is usually the cheaper path, but the honest answer to "how much" is: ask your clinic, because it genuinely varies.

Frequently Asked Questions

What does senior dog bloodwork show? A senior panel shows how the organs and blood cells are doing. The chemistry panel reveals kidney, liver, blood sugar, and electrolyte status; the CBC shows anemia, infection, and clotting; a thyroid test screens for hypothyroidism; and a urinalysis assesses kidney concentrating ability, often flagging kidney disease before the blood does. Together they catch kidney disease, thyroid problems, diabetes, and liver changes, often before symptoms appear.

How do I read my dog's blood test results? Each value is compared to a reference range printed on the report, and flagged high or low values are starting points for discussion, not diagnoses. The most useful thing to look at is the trend across visits rather than a single result, and to let your vet read the panel as a pattern, since one odd value rarely tells the whole story. Bring prior results so the current ones can be compared.

How often should a senior dog have bloodwork? Healthy dogs around 7 to 10 usually have a panel once a year; over about 10, or with a chronic condition, most vets recommend twice a year. Dogs managing a diagnosed disease often need testing every 3 to 4 months. More frequent testing catches a developing problem earlier by giving the trend more chances to show.

What is SDMA, and should I ask for it? SDMA is a kidney marker that rises earlier than the traditional creatinine test, at around a 40% decrease in GFR versus almost 75% for creatinine (IDEXX), and it is not skewed by low muscle mass, which matters in older dogs. Because it catches kidney disease earlier, it is worth asking whether your senior panel includes it.

Can bloodwork be normal and my dog still be sick? Yes. Bloodwork is powerful but not all-seeing. Some conditions, including certain cancers, early heart disease, and some hormonal problems, may not show on a standard panel, which is why bloodwork is paired with a physical exam, urinalysis, and sometimes imaging. Normal results are reassuring but not a guarantee, and any ongoing symptom still deserves a look.

Sources

  • IDEXX Laboratories, SDMA. Source of the 40% and 75% figures quoted above. idexx.com
  • Hall JA, Yerramilli M, Obare E, Yerramilli M, Almes K, Jewell DE. Serum Concentrations of Symmetric Dimethylarginine and Creatinine in Dogs with Naturally Occurring Chronic Kidney Disease. Journal of Veterinary Internal Medicine, 2016;30:794-802. Reports that serum SDMA increased before creatinine in 17 of 19 dogs, mean 9.8 months, range 2.2 to 27.0 months. Authors, journal, volume, pages and finding re-checked against the published record on 2026-09-10; PMC hosts the open-access full text but answers automated requests with a captcha, so the finding is transposed rather than quoted. doi.org/10.1111/jvim.13942
  • Antech Diagnostics, KeyScreen GI Parasite PCR Fecal Test for Dogs & Cats (panel contents and hookworm resistance marker).
  • AAHA 2023 Senior Care Guidelines for Dogs and Cats (senior wellness screening, semi-annual exams and diagnostics). https://www.aaha.org/resources/2023-aaha-senior-care-guidelines-for-dogs-and-cats/

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About the Author

Sarah Bennett researches senior dog care from a home centered on her Border Collie, Lucy. I am not a veterinarian; I write from a researcher and owner's perspective and check what I can against published veterinary sources, including the IDEXX material on SDMA cited above. The reason I keep coming back to the trend and to the urine test with senior dog bloodwork is that they are the two things most owners are never told, and for catching disease early in an older dog, they are where the value hides.

Leo Bennett co-writes Senior Dog Daily with Sarah, sharing the research and the writing.