Basophils
Blood count (CBC) ·Also called: BASO, basophil count, basophilia
What it is
Basophils release histamine and other mediators of allergic and inflammatory responses, working closely with the tissue-resident mast cells they resemble. Their numbers in blood are tiny, and analysers can miscount them, so a flagged value is often confirmed on a smear.
Why your vet measures it
Basophilia is uncommon enough that when it is real, it narrows the field quickly — most often to parasitic disease, heartworm, or a mast cell tumour. On its own, without other findings, it rarely changes management.
What a high result can mean
- Heartworm disease, classically with eosinophilia alongside
- Other parasitic infections
- Allergic or hypersensitivity disease
- Mast cell tumours and, rarely, myeloproliferative disease
What a low result can mean
- Not interpretable — a count of zero is normal in healthy dogs and cats
Questions worth asking your vet
- Was this confirmed on a blood smear, or is it an analyser count?
- Given where we live, is heartworm testing worth doing?
Related terms
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