The animals who do best long-term aren't necessarily the ones with the fewest problems — they're the ones whose problems are found early. Every week in my practice I see the difference that a timely blood panel makes: the cat whose kidney disease was caught at stage one and managed for years, versus the one who came in in crisis at stage four. The cat didn't become sicker faster; the disease was just never looked for.
Screening tests change that dynamic. Here are the key ones, what they actually look for, and when your pet should be having them.
1. Complete Blood Count (CBC)
The CBC is the cornerstone of any diagnostic panel and is typically included in every routine wellness screen.
It measures:
- Red blood cells (RBCs) — quantity (are there enough to carry oxygen?) and morphology (what shape and size are they?)
- Haemoglobin — oxygen-carrying capacity
- Packed cell volume (PCV) / haematocrit — the percentage of blood volume that is red cells
- White blood cells (WBCs) — total count and differential (which types, in what proportion)
- Platelets — important for normal clotting
Conditions the CBC can detect include anaemia (from blood loss, destruction, or underproduction), infection, inflammatory disease, leukaemia and some other cancers, immune-mediated disorders, and clotting abnormalities.
When to screen: From first wellness visit; at every annual exam for adults; more frequently for seniors or animals under treatment.
2. Biochemistry Panel (Organ Function Screen)
The chemistry panel is where organ health lives. It's a snapshot of how well the liver, kidneys, pancreas, and metabolic systems are functioning at the time of the blood draw.
Key markers include:
- ALT (alanine aminotransferase) — liver cell enzyme; elevated when liver cells are damaged
- ALP (alkaline phosphatase) — liver and bone; elevated in liver disease, Cushing's syndrome, and some medications
- Creatinine and BUN (blood urea nitrogen) — kidney waste products; elevated when kidneys aren't filtering adequately
- SDMA (symmetric dimethylarginine) — a more sensitive early kidney marker that detects dysfunction when approximately 25% of kidney function is lost, compared to roughly 75% loss typically required before creatinine rises above reference range
- Glucose — elevated with diabetes; low in some insulinomas or severe illness
- Total protein and albumin — nutritional status and protein loss
- Electrolytes (sodium, potassium, chloride) — critical for cardiac and muscular function
When to screen: Annually for pets over five to seven; baseline recommended for any pet starting a new long-term medication.
3. Urinalysis
Blood tests alone don't tell the complete story about kidney function. Urine must be evaluated alongside chemistry values to interpret them properly.
A full urinalysis assesses:
- Specific gravity — how concentrated the urine is; dilute urine in a cat or dog that's drinking excessively is significant
- pH — relevant for urinary crystal and stone formation
- Protein — persistent proteinuria indicates glomerular damage (the kidney's filtering units)
- Glucose — glucose in urine suggests blood glucose has exceeded the renal threshold, supporting diabetes
- Bilirubin — may indicate liver disease or haemolysis
- Sediment — examined under the microscope for cells, casts, crystals, and bacteria
A urine culture may follow if the sediment suggests bacterial infection — urinalysis alone can't identify the species or antibiotic sensitivity of the bacteria involved.
When to screen: Annually from middle age; whenever increased drinking or urination is reported; as part of monitoring for pets with known kidney, liver, or endocrine disease.
4. Thyroid Panel
Thyroid disease is common enough in both species to warrant routine screening in older pets — but it presents very differently.
In cats: Hyperthyroidism (overactive thyroid) is the most common endocrine disorder in cats over ten. It causes weight loss despite good appetite, vocalisation, restlessness, vomiting, a rapid heart rate, and a characteristic unkempt coat in advanced cases. A total T4 is the primary screening test; when borderline, a free T4 adds sensitivity.
In dogs: Hypothyroidism (underactive thyroid) is more common. Weight gain, lethargy, hair loss and poor coat, cold intolerance, and skin thickening are typical signs. A full thyroid panel — TSH plus free and total T4 — is needed for accurate diagnosis.
When to screen: Cats from age seven or eight onwards at every annual exam; dogs when clinical signs suggest hypothyroidism; certain breeds known to be predisposed to hypothyroidism (Golden Retrievers, Dobermanns, Cocker Spaniels) may warrant earlier screening, though screening guidelines vary between veterinary organizations.
5. Blood Pressure Measurement
Hypertension in pets is a consequence rather than a cause — it almost always occurs secondary to kidney disease, hyperthyroidism, hyperadrenocorticism (Cushing's), or diabetes. But its secondary effects are severe: hypertensive retinopathy can cause sudden blindness, and sustained high pressure accelerates kidney damage.
Measuring blood pressure in a clinic setting requires patience — anxious animals have transient blood pressure elevations that don't reflect their resting state. Multiple readings, taken after the animal has settled, give a more reliable picture. High-definition oscillometric devices designed for veterinary use have made this much more practical.
When to screen: At annual exams for all senior pets; routinely for any animal with kidney disease, hyperthyroidism, diabetes, or Cushing's syndrome.
6. Faecal Parasite Screening
Intestinal parasites — roundworms, hookworms, whipworms, giardia, coccidia — shed eggs or cysts in faeces. Faecal flotation concentrates and identifies these under the microscope. PCR-based faecal panels detect a wider range of pathogens, including some that don't show up reliably on standard flotation.
Animals can carry intestinal parasites without overt diarrhoea or weight loss. Roundworms and hookworms are also zoonotic — transmissible to humans — which adds a public health dimension beyond pet wellness.
When to screen: Annually for all dogs and cats; every six months for dogs with outdoor exposure or those in multi-dog households; immediately for any new pet before introduction to resident animals.
7. Heartworm Testing
Heartworm disease is a mosquito-transmitted parasitic infection that establishes in the pulmonary arteries and, in later stages, the right side of the heart. Annual antigen testing for dogs detects the presence of adult female heartworms — a critical check even for dogs on prevention, since no preventive is 100% reliable and a lapse in dosing may not be immediately obvious.
Testing in cats is more complex — standard antigen tests have lower sensitivity in cats, and antibody tests may be more informative. Discuss the appropriate approach with your vet.
When to screen: Annually for all dogs in endemic areas before continuing prevention; at least once as a baseline for cats in endemic areas.
8. Orthopaedic and Screening Radiographs
For high-risk breeds, elbow and hip radiographs before breeding or during early adulthood can detect dysplasia before clinical signs develop.
Chest radiographs serve a different role — as part of a staging workup when a mass is found, to evaluate cardiac enlargement identified on auscultation, or to assess lung health in animals with respiratory signs.
Building a Screening Schedule
The annual wellness examination is the anchor point for most of these tests. Your vet will help you decide which tests are appropriate given your pet's age, species, breed, lifestyle, and medical history.
Understanding these diagnostics as part of a preventive care program — rather than as responses to illness — is the mindset shift that makes the difference. Once you understand what each value in a blood panel actually means, these results go from intimidating numbers to genuinely useful information about your animal's health.
Frequently Asked Questions
At what age should pets start getting blood panels?
Young, healthy pets may not need full blood panels at every visit, though a baseline panel in young adulthood is useful for comparison later. Most vets recommend routine annual bloodwork from age five to seven in dogs and cats. For breeds with known predispositions to early organ disease, earlier screening is reasonable.
Can screening tests give false results?
Yes, both false positives and false negatives occur. Single elevated values don't diagnose disease — they direct further investigation. A mildly elevated kidney marker, for instance, is a reason to retest and assess urine concentration, not to conclude kidney disease. Context — the full panel, the clinical exam, the patient history — always matters more than a single number.
How much does a full wellness screening panel cost?
Costs vary considerably between practices and regions. A CBC plus biochemistry panel plus urinalysis is the core of most wellness screens. Some practices offer discounted wellness packages. The cost of treatment for late-stage disease — kidney failure, uncontrolled diabetes, advanced cardiac disease — typically far exceeds the cumulative cost of the screening panels that would have caught the condition earlier.
Are there screening tests specific to cats?
Yes. Cats have several unique priorities: total T4 for hyperthyroidism from middle age onward, SDMA as an early kidney marker (cats are particularly susceptible to chronic kidney disease), blood pressure measurement, and in some cases FIV/FeLV antibody testing if there's any outdoor exposure or unknown history. Cat and dog wellness panels often look similar but the interpretive thresholds and clinical significance of specific values differ between species.