Basophils
Smallest subgroup of white blood cells, measured in the blood differential
Also known as
Definition
Basophils are one of the five types of white blood cells and make up the smallest share. They release enzymes during allergic reactions and asthma attacks. They are measured in the blood differential, which breaks white blood cells down into neutrophils, lymphocytes, monocytes, eosinophils and basophils, as a percentage and often also as an absolute count.
| Parameter | Value |
|---|---|
| Unit | % of white blood cells; absolute count as /nl (= 10⁹/l) |
| Reference Range | About 0.5–1% of white blood cells in adults. Some labs use their own ranges and also report absolute counts; the reference range on your own report is what counts. Discuss any deviation with your doctor. |
Agree on your personal target range with your doctor.
↓ What a low value means
A lower share of basophils can be linked to acute infections, cancer or severe injuries. The percentage also drops arithmetically when another type of white blood cell rises sharply. That is why the value is always read together with the rest of the blood count. Discuss the result with your doctor.
↑ What a high value means
A higher share can be linked to allergic reactions, chickenpox, collagen vascular diseases (inflammatory connective tissue disorders), a past removal of the spleen or myeloproliferative bone marrow disorders such as chronic myeloid leukemia. An unusual value alone is not a diagnosis; further tests often follow. Discuss the result with your doctor.
When to test
Basophils are measured in a complete blood count with differential, for example during routine checkups, when an infection is suspected, with unexplained tiredness, weakness or bruising, or to monitor a known blood disorder. No special preparation is needed. Smoking, alcohol, injuries and severe stress can affect the white blood count.
Frequently asked questions
Why does my report show basophils as a percentage and as an absolute count? +
The percentage shows their share of all white blood cells, while the absolute count shows the amount per volume of blood. If another type of white blood cell rises sharply, the basophil percentage can fall even though their absolute count stays the same.
Are basophils related to allergies? +
Yes. Basophils release enzymes during allergic reactions and asthma attacks. A higher share can be linked to an allergic reaction, but it also has other possible causes.
Do I need to fast for a blood differential? +
No, no special preparation is needed. The sample is taken from a vein like any other blood draw.
Should a slightly unusual basophil value worry me? +
Unusual values do not always mean a condition that needs treatment. Doctors interpret them together with symptoms, medical history and other blood results; discuss your result with your doctor.
Basophils
Sources
Last updated: October 05, 2026
This information is for orientation only and does not replace medical advice. Reference ranges can vary by laboratory, method and country.