Most people start looking up pet blood work when a vet recommends it at a check-up, before anaesthetic, or after a worrying change at home. The question underneath is usually the same: what are they looking for, and what happens if something comes back “off”?
Blood tests don’t diagnose every condition on their own, but they do show how the body is coping—oxygen-carrying cells, signs of inflammation, hydration, and the workload on organs like the liver and kidneys. Used well, they help your vet make calmer, safer decisions, especially when a pet looks fine on the outside.1, 2
What pet blood work is (and what it isn’t)
“Blood work” is a general term for laboratory tests run on a small blood sample. In everyday practice it usually means a complete blood count (CBC) and a biochemistry (chemistry) panel, sometimes with extra tests added depending on age, symptoms, and risk factors.1, 2
It’s best thought of as a map, not a verdict. Results can point towards dehydration, infection, anaemia, organ stress, endocrine disease, and more—but interpretation depends on the whole picture: exam findings, history, medications, diet, and sometimes repeat testing.1, 2
Common blood tests your vet may recommend
- Complete blood count (CBC): measures red blood cells, white blood cells, and platelets (clotting cells). Helps screen for anaemia, inflammation/infection patterns, and platelet problems.1, 2
- Biochemistry (chemistry) panel: looks at chemical markers linked to organs and metabolism (for example kidney and liver markers, glucose, proteins, and electrolytes). Helps assess organ function and body chemistry.1, 2
- Targeted add-ons: thyroid hormones, pancreatitis markers, infectious disease testing, or other specific tests when clinically indicated.1
Why blood work matters for pets
Animals are good at carrying on as normal while illness develops quietly. Blood work helps catch problems that don’t announce themselves in obvious ways—especially early kidney disease, metabolic issues, and some causes of lethargy, weight loss, vomiting, increased drinking/urination, or poor recovery after exertion.1, 2
Diagnosis when something seems “not quite right”
When a pet is unwell, blood work can narrow the field. A CBC may show patterns consistent with inflammation, blood loss, or reduced red cell production. A chemistry panel can highlight dehydration, glucose changes, electrolyte imbalance, or markers suggesting liver or kidney involvement.1, 2
Monitoring ongoing conditions and medication safety
For chronic conditions, repeat blood tests help your vet see trends over time, not just a single number on a single day. Monitoring is also used to check how well a treatment plan is working, and to watch for side effects with medicines that can affect organs or blood cell lines.1, 2
Baseline testing, especially as pets age
A “normal-for-your-pet” baseline is useful. If results change later, your vet has something to compare against. Many senior-care guidelines recommend regular screening (often including CBC, chemistry, and urinalysis) once pets reach their senior years, with frequency guided by individual risk and health status.3
When blood work is usually done
Routine check-ups (wellness screening)
Blood tests aren’t automatically needed at every visit, but they’re commonly recommended during annual or senior health checks—particularly if a pet is older, has a known condition, or has subtle changes that are easy to miss in day-to-day life.4, 3
Before surgery or dental procedures (pre-anaesthetic testing)
Pre-anaesthetic blood work helps identify issues that may increase anaesthetic risk, particularly problems involving the kidneys, liver, red blood cells, and electrolytes. If something important is detected, your vet may adjust the anaesthetic plan, add intravenous fluids, schedule further testing, or postpone the procedure if needed.5, 6
When symptoms appear
If your pet develops vomiting, diarrhoea, lethargy, weight change, poor appetite, increased thirst/urination, pale gums, bruising, or unexplained pain, blood work is often one of the first steps. It helps your vet decide what to treat now, what to monitor, and what to investigate next.1, 2
What happens during the blood work process
How the sample is collected
A vet or nurse usually collects blood from a vein—commonly in a front leg, back leg, or the jugular vein in the neck. The collection itself is brief. Some pets need gentle restraint; a few need extra time, a quiet room, or a different approach if they’re anxious or wriggly.1, 7
What the lab does with it
Some clinics run common panels in-house; others send samples to an external laboratory. The lab measures cell counts and chemical markers, and flags results outside the expected range. Your vet then interprets what matters for your pet’s age, breed, history, and current signs.1, 2
How long results take
Timing varies. In-house tests can sometimes be available the same day (or within minutes for some pre-anaesthetic panels), while external lab work is often returned within a day or two, depending on the tests requested and transport times.6
Understanding results without getting lost in the numbers
Blood reports can look dense because they’re built for clinical comparison. The key is not a single highlighted value, but the pattern: which values moved together, by how much, and whether they fit the story your pet is telling on examination.1, 2
CBC: the cell side of the story
- Red blood cells: relate to oxygen delivery. Low counts can suggest anaemia (from blood loss, destruction, or reduced production).1, 2
- White blood cells: help interpret inflammation, infection, stress responses, and some immune conditions. High or low numbers can both matter, depending on context.1, 2
- Platelets: involved in clotting. Low platelets can raise concern for bleeding risk, and may change what procedures are safe today.2, 8
Chemistry panel: organs, hydration, and body balance
Chemistry results commonly include markers that help assess kidney and liver function, hydration status, protein levels, blood sugar, and electrolytes. Abnormal results can reflect disease, but they can also be influenced by stress, recent meals, medications, or dehydration—so your vet may recommend repeat testing or pairing results with a urinalysis for a clearer view.1, 2
Questions worth asking your vet
- Which results are most important for my pet right now?
- Could stress, fasting status, dehydration, or medication have shifted these numbers?
- Do we need a recheck to confirm a trend, or a different test (like urinalysis or imaging) to explain the change?1, 3
Conditions blood work commonly helps detect or monitor
Blood work is used to detect or support diagnosis of many common problems, including:
- Anaemia and other blood cell disorders (CBC patterns).1, 2
- Inflammation/infection patterns (white blood cell changes).1, 2
- Kidney and liver disease (chemistry markers, often alongside urinalysis).1, 2, 3
- Diabetes and some other metabolic issues (glucose and related markers).2
- Thyroid disease (with specific hormone tests, especially in older pets).3
If a result is abnormal, the next step isn’t always treatment straight away. Sometimes it’s a repeat test after hydration, a urine test, or a more specific blood test to confirm what the first panel hinted at.1, 3
Preparing your pet for blood work
Keeping the visit low-stress
- Keep arrivals calm and unhurried; stress can affect some readings and can make sampling harder.2
- Bring a familiar blanket or towel to help your pet settle on the table or in your lap.
- If your pet is very anxious, ask the clinic about quieter appointment times or fear-minimising handling options.
Fasting: when it matters
Some tests are best done fasting (often around 8–12 hours), particularly those affected by recent food intake. Your clinic will tell you when fasting is needed for the specific panel being run. Water is usually allowed, but always confirm for your pet and situation.2
If your pet takes regular medication, ask whether to give it as normal before the test. The right answer depends on what’s being measured and why.1
Cost and access in Australia (what’s realistic)
Pricing varies widely by clinic, location, and what’s included (in-house vs external lab, “mini” pre-anaesthetic panels vs full profiles, and whether urinalysis or other add-ons are needed). The most useful figure is the one your vet can quote for your pet’s specific plan, before the sample is taken.
Access is usually straightforward in metropolitan areas. In rural and regional areas, blood can still be collected locally, but some clinics may send samples to external laboratories, which can add time for results depending on transport schedules.1
Final thoughts
Blood work is one of the quiet, practical tools of veterinary care. It can reveal strain and imbalance long before the body runs out of ways to compensate, and it can also confirm when things really are steady. The best results come when the numbers are read alongside the living animal in front of your vet—breathing, blinking, shifting weight, and telling its own story.1, 4
References
- Merck Veterinary Manual (Pet Owner Version) — Veterinary medical tests
- Merck Veterinary Manual (Pet Owner Version) — Common laboratory tests in veterinary medicine
- AAHA — Diagnostic tests and recommended frequencies for senior dogs and cats (2023 Senior Care Guidelines table)
- The University of Sydney Veterinary Teaching Hospital — Routine health care
- Karingal Veterinary Hospital — Preanaesthetic blood testing
- Weston Creek Veterinary Hospital — Pre-anaesthetic blood tests
- RSPCA Knowledgebase — Why do pets need blood transfusions and how can my dog or cat help?
- Doyalson Animal Hospital — Blood testing (full blood count and biochemistry overview)
Veterinary Advisor, Veterinarian London Area, United Kingdom