Basophils
Also written as: absolute basophil count, basos
The rarest white blood cell, involved in allergic and inflammatory responses.
What it measures
The number of basophils in the blood. Basophils are the least numerous type of white blood cell and are normally present in very small numbers. They release histamine and other chemicals during allergic and inflammatory responses.
Why a doctor orders it
It is not ordered on its own - it arrives as part of the white cell differential on a complete blood count and is mostly reviewed for completeness alongside the other white cell types.
What is generally associated with a higher result
Broadly associated with allergic responses, some forms of chronic inflammation. A persistent, marked elevation is one of the findings that can prompt evaluation for certain chronic blood disorders, but small fluctuations are common and rarely meaningful.
What is generally associated with a lower result
Broadly associated with acute stress, acute infection, an overactive thyroid, and corticosteroid medicines. Because the normal count is already very small, low values are generally not pursued.
Everyday things that move this number
Not every shift in a value reflects disease. These are ordinary factors known to affect this particular measurement:
- Analyzer imprecision - automated counters are least accurate for the rarest cell types
- A recent allergic flare or allergy season
- Corticosteroid medicines
- Recent illness or physical stress
Questions to take to your appointment
- Was this an automated count, and would a manual review of the blood smear confirm it?
- Is this isolated, or are other white cell types shifted too?
- Could allergies or my thyroid be relevant to this value?
Build a printable questionnaire with your own results →
Where to read more
MedlinePlus, from the US National Library of Medicine, publishes patient-facing pages on individual lab tests and is a reliable next stop: medlineplus.gov/lab-tests .
Support this site
This site is free, has no paywall, and takes no money from hospitals, insurers, or billing companies. If it helped, a coffee keeps it going.
Buy us a coffee