Blood work is the most important diagnostic tool in veterinary medicine -- and the results sheet you get from your vet can be confusing. Understanding what each value means empowers you to be a better advocate for your cat's health and have more productive conversations with your veterinarian.
Complete Blood Count (CBC)
| Test | What It Measures | High Means | Low Means |
|---|---|---|---|
| RBC (Red Blood Cells) | Oxygen-carrying cells | Dehydration, bone marrow disease | Anemia (blood loss, chronic disease, bone marrow failure) |
| WBC (White Blood Cells) | Immune cells | Infection, inflammation, stress, leukemia | Bone marrow suppression, overwhelming infection, FeLV |
| Platelets | Clotting cells | Inflammation, iron deficiency | Bleeding risk, bone marrow disease, DIC |
| Hematocrit (HCT/PCV) | Percentage of blood that is red cells | Dehydration | Anemia |
Chemistry Panel
| Test | What It Measures | High Means | Low Means |
|---|---|---|---|
| BUN (Blood Urea Nitrogen) | Kidney waste product | Kidney disease, dehydration | Liver disease, low protein diet |
| Creatinine | Kidney waste product (more specific) | Kidney disease | Muscle wasting |
| SDMA | Early kidney marker | Early kidney disease (before creatinine rises) | N/A |
| ALT | Liver enzyme | Liver damage/inflammation | Usually not significant |
| ALP | Liver/bone enzyme | Liver disease, bone growth (kittens) | Usually not significant |
| Glucose | Blood sugar | Diabetes, stress (very common in cats) | Insulin overdose, sepsis, liver failure |
| Total Protein | Albumin + globulin | Dehydration, inflammation, FIP | Liver disease, kidney loss, malnutrition |
| T4 (Thyroid) | Thyroid hormone level | Hyperthyroidism | Hypothyroidism (rare in cats), sick euthyroid |
The Stress Glucose Problem
Cats are notorious for stress hyperglycemia -- blood glucose can spike to 300-400 mg/dL from the stress of a vet visit alone. This does NOT mean the cat is diabetic.
- Fructosamine test: Measures average blood sugar over 2-3 weeks, unaffected by stress
- If glucose is high on a single blood test: fructosamine differentiates stress from diabetes
How Often Should Cats Get Blood Work?
- Young healthy cats (1-6): Baseline, then every 2-3 years
- Mature cats (7-10): Annually
- Senior cats (11+): Every 6 months
- Cats on medication: As directed (often every 3-6 months)
- Sick cats: As needed for monitoring
Frequently Asked Questions
My cat's kidney values are slightly elevated -- should I panic?
Mildly elevated kidney values (especially BUN) can be caused by dehydration, recent high-protein meal, or early kidney changes. A single slightly elevated result does not confirm kidney disease. Your vet will likely recommend: recheck in 2-4 weeks (fasted, well-hydrated), SDMA test (catches early changes), and urinalysis (urine concentration is key). Trending values over time is more important than a single number. If SDMA is also elevated and urine is dilute, early CKD management should begin.
