White blood cells (WBC)
Blood count (CBC) ·Also called: WBC, leukocytes, white cell count, white blood cell count
What it is
White cells are the body's defence and clean-up crew. The total count sums neutrophils, lymphocytes, monocytes, eosinophils and basophils. Most reports print the total first and then break it down, either as percentages or as absolute counts.
Why your vet measures it
Infection, inflammation, stress, and cancers of the immune system all move this number, and so does simple excitement. Because those causes pull in different directions and can cancel out, a normal total does not rule out a problem — which is why the breakdown matters more than the headline.
What a high result can mean
- Bacterial infection or inflammation anywhere in the body
- The stress or steroid pattern, which raises neutrophils while dropping lymphocytes and eosinophils
- Excitement during handling, especially in cats, which can briefly double the count
- Leukaemia or lymphoma, usually with a striking rise in one specific cell type
What a low result can mean
- Overwhelming infection consuming cells faster than they are produced, as in sepsis or a ruptured gut
- Viral disease — parvovirus in dogs, panleukopenia, FeLV or FIV in cats
- Bone marrow suppression from disease, chemotherapy, or certain drugs
Dogs and cats differ
Cats show a distinct physiological leukocytosis: adrenaline from a car journey and a strange consulting room can push both neutrophils and lymphocytes up within minutes, with no illness at all. In dogs, the steroid pattern is more common and goes the other way for lymphocytes.
Questions worth asking your vet
- Which cell type is driving the change in the total?
- Could stress or excitement at the appointment explain this?
- Is there a left shift — immature neutrophils — suggesting an active infection?
Related terms
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