Blood Tests for Dogs and Cats: What Results Can Tell You
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By Dr Duncan Houston
A blood-test report can contain dozens of abbreviations and a few worrying red flags. Those numbers are useful, but they are only part of the picture. Understanding why your vet chose the tests and what decisions the results might change makes the report easier to discuss.
Quick Answer
Blood tests help assess blood cells, body chemistry and selected diseases in dogs and cats. Results must be interpreted alongside symptoms, examination findings, medications and sometimes urine tests or imaging. A flagged value does not automatically diagnose disease, while results within the reference interval do not rule out every problem.
Why might your pet need blood work?
Your vet may recommend testing to investigate signs such as weight loss, increased thirst, vomiting or weakness. Testing can also monitor a known condition, check the effects of medication or establish a baseline during preventive care.
Before anaesthesia, appropriate tests may identify abnormalities that influence the plan or require treatment first. They cannot guarantee a risk-free procedure. AAHA's preanaesthetic guidance places laboratory testing within an individual assessment that also considers history, examination and other risks.
The useful question is not simply “Should every pet have every test?” Ask what the proposed panel is intended to investigate and how the findings could change care.
Common tests explained
| Test | What it examines | Important limitation |
|---|---|---|
| Complete blood count, or CBC | Red cells, white cells and platelets | Changes suggest categories of problems but often need further interpretation. |
| Biochemistry panel | Measures such as glucose, proteins, electrolytes and organ-related markers | The contents vary between panels, and a marker is not always specific to one disease. |
| Hormone testing | Selected endocrine conditions, such as thyroid disorders | Some diagnoses require several measurements or specialised testing. |
| Infectious-disease testing | Evidence relating to a particular infection or exposure | Timing, geography and confirmation requirements matter. |
| Drug-level testing | Concentration of certain prescribed medicines | Sample timing relative to the dose can be crucial. |
What a CBC can show
Red blood cells carry oxygen. A reduced red-cell measure may indicate anaemia, but the cause could include blood loss, destruction or reduced production. White-cell patterns can change with inflammation, stress and other conditions. Platelets participate in clotting, although platelet count alone does not assess every part of the clotting system.
Sometimes the laboratory examines a blood smear to check cell appearance or investigate an analyser result. Platelets may clump in a sample, particularly in cats, producing a misleadingly low automated count. Your vet may therefore request a manual review or repeat sample before drawing conclusions.
AAHA's dog blood-work explanation outlines the main CBC components, while its cat blood-work guidance describes common feline testing considerations.
What chemistry results can and cannot mean
A chemistry panel provides clues about several body systems. Kidney-related values need context such as hydration and urine concentration. Increased liver enzymes do not, by themselves, mean liver failure. Glucose can be affected by disease, medication and stress, especially in cats.
A normal panel cannot exclude every cancer, heart problem, early disease or local source of pain. If your pet remains unwell, further assessment may still be needed. Conversely, a mildly unusual result in a comfortable pet may be checked again rather than treated immediately.
Understanding reference intervals
The comparison range on a report comes from a reference population and depends on the laboratory's methods. It is not a sharp boundary between health and disease. Age, breed, physiological state and the size and pattern of a change can all affect interpretation.
Cornell's explanation of reference intervals notes that some healthy animals fall outside them. Use the interval supplied with your pet's report rather than a range found on another website. Trends over time may be more informative than one isolated number.
Preparing for the appointment
- Ask whether fasting is necessary and follow the clinic's exact instructions.
- Do not withhold food from a puppy, kitten or diabetic pet, or change insulin or other medication, without specific advice.
- Bring a medication list, previous results and a record of symptoms.
- Ask whether a urine sample is needed and how it should be collected or stored.
- Tell the team about fear of handling so they can plan a calmer visit.
Cornell's urinalysis guidance explains why urine findings often add important information when interpreting blood chemistry. Do not restrict water to make collection easier.
After collection and when to expect results
A small clipped patch and brief pressure over the collection site are common. Follow instructions about removing any temporary bandage. Contact the clinic if bleeding continues, swelling increases or the limb seems painful.
Some tests are available during the visit; others go to an external laboratory. Before leaving, confirm who will contact you, when to expect an update and what to do if your pet worsens while you wait.
Collapse, breathing difficulty, inability to urinate, severe weakness or uncontrolled bleeding need urgent care regardless of whether blood tests have already been booked.
Costs and useful questions
Prices vary with the panel, laboratory, location and whether consultation or sample collection is included. Ask for an itemised estimate rather than relying on a universal online price. If finances are limited, explain that early so your vet can discuss which tests are most likely to change the immediate plan.
Frequently Asked Questions
Does one high result mean my pet is seriously ill?
Not necessarily. Ask how abnormal it is, whether related results support it and what follow-up is recommended.
Why repeat a test?
A repeat can confirm a finding, track change or assess treatment. Ask what interval and sample conditions are needed.
Are dog and cat ranges interchangeable?
No. Species and laboratory methods matter, and young animals may differ from adults.
Can I request a copy?
Yes. Keep the complete report with units, reference intervals and dates, alongside your vet's interpretation.
If you would like help understanding the terminology in your pet's report or preparing follow-up questions, ASK A VET™ can support that conversation with your treating vet.
