FrançaisWhat a CBC measures
The CBC is run on blood collected in an EDTA tube (usually purple-topped), which keeps the cells from clotting [1]. An analyser counts and sizes the cells, and a blood smear examined under the microscope checks their appearance and confirms counts the machine can get wrong, such as platelets [2].
The report has three blocks: the red cells (erythrogram), the white cells (leukogram) and the platelets. It is often paired with a chemistry panel, which measures substances dissolved in the blood, such as ALT or ALP.
Units can look different from one laboratory to another, but many are equivalent: 10⁹/L, G/L and 10³/µL (K/µL) give the same number for white cells and platelets [3].
How to read a CBC line
Every line follows the same pattern. Here is an example from the red cell block.
- Abbreviation HCT, or PCV (packed cell volume): the share of the blood volume occupied by red cells.
- Result 31% of the blood volume is made of red cells in this sample.
- Unit %. Some laboratories write it as L/L (0.31 L/L = 31%).
- Laboratory interval The example uses the dog interval of the Merck Veterinary Manual [3]. Your laboratory’s interval applies to your dog.
- Flag L: below the interval. A low haematocrit describes anaemia; it does not say why.
Red cells: RBC, HGB, HCT and the indices
| Line | What it measures | Example dog interval [3] |
|---|---|---|
| RBC | Number of red blood cells. | 4.95–7.87 × 10⁶/µL |
| HGB (haemoglobin) | The protein that carries oxygen. | 11.9–18.9 g/dL |
| HCT / PCV | Share of the blood occupied by red cells. | 35–57% |
| MCV | Average size of the red cells. | 66–77 fL |
| MCHC | Average haemoglobin concentration in the red cells. | 32.0–36.3 g/dL |
| RETIC (reticulocytes) | Young red cells just released by the bone marrow. | 0–1.0% |
When the haematocrit is low, the reticulocyte count helps tell whether the bone marrow is responding by producing new red cells. A high haematocrit is often seen with dehydration, because the same cells are in less fluid.
White cells: WBC and the differential
The total white cell count (WBC) is followed by the “differential”: the number of each type. Absolute counts (in 10⁹/L or 10³/µL) are more useful than percentages, because a percentage can change only because another type has changed.
| Line | Main role | Example dog interval [3] |
|---|---|---|
| WBC | All white cells together. | 5.0–14.1 × 10³/µL |
| NEUT (segmented neutrophils) | First line of defence against bacteria; increase with inflammation. | 2.9–12.0 × 10³/µL |
| LYMPH (lymphocytes) | Immune memory and antibodies. | 0.4–2.9 × 10³/µL |
| MONO (monocytes) | Cells that clean up tissue damage. | 2–10% of white cells |
| EOS (eosinophils) | Involved in allergies and parasites. | 0–9% of white cells |
| BASO (basophils) | Rare cells linked to allergic reactions. | 0–1% of white cells |
The patterns vets look for
Values that move together often tell more than any single line. Two patterns are especially common in dogs.
- The stress leukogram. Cortisol, released by the body during illness or given as a medicine, typically raises neutrophils and monocytes and lowers lymphocytes and eosinophils. Not every change is present; a low lymphocyte count is the most consistent one [4]. In dogs it often comes with a higher ALP [4]. Its absence in a sick dog can be one reason to check cortisol with an ACTH stimulation test.
- The inflammatory pattern. Neutrophils rise, sometimes with young “band” neutrophils released early by the bone marrow, a sign of strong demand [4].
- Anaemia with or without response. A low haematocrit with many reticulocytes suggests the marrow is replacing lost or destroyed red cells; without them, the marrow may not be keeping up. See anemia in dogs.
- Low platelets. Checked first on the smear, because clumps in the tube are a frequent cause of falsely low counts [2]. See our article on low platelets in dogs.
What can skew a CBC
- Excitement during sampling: adrenaline can briefly raise neutrophils and lymphocytes, an effect seen most often in young animals and in cats [4].
- Dehydration, which concentrates the red cells and raises the haematocrit.
- A sample that clotted or waited too long before analysis: platelet counts fall with storage, and a clotted tube invalidates the count [2].
- Recent medicines, especially corticosteroids [4].
Results often read with the CBC
See how a full blood count is explained in Monty’s sample report. The white cells are detailed in white blood cell count in dogs and eosinophils in dogs and cats. En français : la prise de sang du chien.
Questions to ask your veterinarian
- Which lines are outside the interval, and do they form a pattern?
- Was a blood smear examined, and did it confirm the counts?
- Could stress, dehydration or a medicine explain part of the results?
- Do we need to repeat the CBC, and when?
- How do these results fit with the chemistry panel and the examination?
Get your dog’s full blood count explained, line by line.
AI DiagAnimals reads every line of the report with your laboratory’s own intervals, groups the values that belong together and prepares the questions for your vet. The service opens soon: leave your email to be told first.
Frequently asked questions
What does a CBC test show in dogs?
It counts and describes red cells, white cells and platelets. It can show anaemia, signs of inflammation or infection, a stress pattern or a low platelet count, which your vet then interprets with the examination and other tests [1, 4].
When should I worry about CBC results?
Talk to your vet about any flagged value, but the context matters more than the flag. Values just outside the interval in a well dog are common. Several related changes, a marked change or any symptoms deserve prompt attention.
What is a normal CBC range for a dog?
Each laboratory sets its own intervals. As an example, the Merck Veterinary Manual lists a haematocrit of 35–57%, white cells of 5.0–14.1 × 10³/µL and platelets of 211–621 × 10³/µL for dogs [3].
Can a CBC detect leukaemia in dogs?
A CBC can show very high counts or abnormal cells that make the vet suspect a blood cancer, but confirming it needs further tests such as a smear review by a pathologist [4]. A normal CBC does not rule out every cancer.
Do dogs need blood work every year?
Your vet recommends a schedule based on age, breed, medicines and health. Senior dogs and dogs on long-term medication are usually tested more often, which also gives a baseline for comparison.
Sources
- eClinPath, Cornell University College of Veterinary Medicine. Sample collection (chemistry and hematology tubes). eclinpath.com/chemistry/sample-collection-chem
- eClinPath, Cornell University College of Veterinary Medicine. Platelet number. eclinpath.com/hemostasis/tests/platelet-number
- Merck Veterinary Manual. Hematology (complete blood count) reference ranges. merckvetmanual.com/reference-values-and-conversion-tables/reference-guides/hematology-reference-ranges
- eClinPath, Cornell University College of Veterinary Medicine. Leukogram patterns. eclinpath.com/hematology/leukogram-changes/leukogram-patterns
Laboratory methods and reference intervals vary. This article explains; it does not diagnose. For a decision about your pet, use the original report and talk to your veterinarian. Our editorial policy.