What are basophils?
Of the five types of white blood cell, basophils are the smallest group: fewer than one in a hundred. Their granules stain dark blue under the microscope and are full of histamine and heparin. In an allergic reaction they recognise the allergen through antibodies on their surface, and release the histamine that widens the vessels, makes the nose run and the skin itch. They are the travelling relatives of the mast cells, which do the same from the tissue. Because there are so few, the count in your blood is coarse: the lab counts only a handful in an ordinary measurement, and the difference between zero and a few hundredths is measurement noise. Every band starts at zero, and that means a low count is never a finding. The count rises slightly with allergy, with an inflammation that has been running longer, such as a bowel inflammation, and with an underactive thyroid. Cortisol and prednisone suppress it, as with the eosinophils. Your report shows the count in ×10⁹/L. Normal is about 0 to 0.15 ×10⁹/L, where the labs overlap. Only a count that persistently sits far above the band is taken seriously, because that is the classic picture of a bone marrow disease in which the production of white cells goes astray.
Why are basophils relevant?
On their own basophils say little, and that is the honest message of this page. They are so scarce that an ordinary measurement can hardly tell normal from slightly raised, and most rises are a mild response to something you already know: an allergy, an inflammation that is running. Anyone reading their blood count and seeing a slightly raised basophil count may usually leave it alone. Where they do add something is in the pattern. With an allergy the eosinophils rise and the basophils sometimes along, while CRP stays normal. With an inflammation that has been running a while the monocytes rise and the basophils sometimes along, with a CRP that stays high. And with an underactive thyroid, which slows the whole body, they rise slightly beside a high TSH. In each of those cases they confirm what the other values already say. The one situation in which basophils play the lead is rare. In chronic myeloid leukaemia, a bone marrow disease in which the production of white cells goes astray, a persistently high basophil count is one of the first signs, beside a strongly raised total of white cells and immature cells on the report. Such a picture stands out in the count and a doctor assesses it the same day. It is the reason a count that repeatedly stays far above the band is checked, even without symptoms.
Basophils reference ranges
What counts beside the number:
- That a low count never means anything, because the band starts at zero
- The eosinophils: if they rise along with a normal CRP, it is an allergy
- The monocytes and CRP: if they rise along, it is an inflammation that has been running a while
- TSH, because an underactive thyroid lifts the count slightly
- Whether you take prednisone or measured in the pollen season
- The total of white cells and immature cells on the report, which say whether the bone marrow is involved
A low count is never a finding here: all labs start at zero. The lab counts only a handful of basophils in an ordinary measurement, so the difference between zero and a few hundredths is noise. Only a count that repeatedly sits far above the band counts, and then together with the total of white cells and the other types.
What Dutch labs actually use
Three labs publish a band here and all three start at zero. The difference sits in the ceiling: Star-shl stops at 0.15, Unilabs and Certe at 0.2. With such a scarce cell that difference is smaller than the measurement noise of an ordinary count.
0.0 – 0.15×10⁹/L
Between 0.15 and 0.2 it depends on the lab, because each sets its limits on its own method and population. Above 0.2 every lab calls it abnormal.
every lab calls 0.0 – 0.15 ×10⁹/L normal. Between 0.15 and 0.2 it depends on the lab.
Every age, per lab
| Laboratory | Group | Reference range |
|---|---|---|
| Unilabs(Saltro, Medlon, SHO, Atalmedial)2026 | Above 15 yrs | < 0.2 ×10⁹/L |
| Star-shl2026 | All ages | 0.0–0.15 ×10⁹/L |
| Certe2026 | Women from 18 yrs | 0–0.2 ×10⁹/L |
| Men from 18 yrs | 0–0.2 ×10⁹/L |
Each band as the lab publishes it, retrieved in 2026, unless marked otherwise.
Basophils high or low: what it means
A low count means nothing. Every band starts at zero, cortisol and prednisone suppress the count with stress, illness and an acute allergic reaction, and an ordinary measurement counts only a handful anyway. There is no lower limit that means anything. A high count usually means a mild response, and the other white cells say to what. With high eosinophils and a normal CRP it is an allergy. With high monocytes and a high CRP it is an inflammation that has been running a while. With a high TSH it is an underactive thyroid. A count that repeatedly stays far above the band, certainly with a strongly raised total of white cells and immature cells on the report, is the picture of a bone marrow disease, and that is assessed the same day. What you do about it: with a mild rise nothing to the basophils themselves, but to the reason. Anyone who treats their allergy sees eosinophils and basophils fall together. Anyone who tackles an inflammation, in the gut, the joints or the gums, sees them fall along with CRP. An underactive thyroid that is treated brings the count back. Measure outside the pollen season and not during a course of prednisone if you want to know your usual level. Never read basophils alone, but beside the eosinophils, which play the lead in an allergy, beside the monocytes and CRP, which show a longer-running inflammation, and beside the total of white cells and the neutrophils, which say whether the bone marrow as a whole is involved.
What lowers it
Not a finding: the band starts at zero.
| Cause | How often |
|---|---|
| CorticosteroidsPrednisone suppresses the count to zero, as with the eosinophils; after the course it comes back | Often |
| Acute allergic reaction or infectionDuring a fierce allergic reaction the cells are emptied and gone from the blood, and with a severe infection your own cortisol suppresses them | Sometimes |
What raises it
Usually a mild response, and the other white cells say to what.
| Cause | How often |
|---|---|
| AllergyHay fever, asthma or eczema; usually the eosinophils lead and the basophils rise slightly along | Often |
| Longer-standing inflammationA bowel inflammation or rheumatoid arthritis; then the monocytes rise too and CRP stays high | Often |
| Underactive thyroidA slight rise beside a high TSH, which disappears when the thyroid is treated | Rare |
| Bone marrow diseaseChronic myeloid leukaemia often begins with persistently high basophils, a strongly raised total of white cells and immature cells on the report | Rare |
How does a basophils blood test work?
- Referral
- Not needed. Basophils are in every blood count with differential, and you can have that measured yourself; requesting them separately makes no sense.
- Fasting
- Not needed; the count does not respond to food or to the time of day.
- When
- Outside the pollen season and not during a course of prednisone if you want to know your usual level. Otherwise the moment matters little.
- The draw
- One tube of blood from a vein in your arm. The lab counts the white cells and sorts them into five types; with such a scarce cell the difference between zero and a few hundredths is measurement noise.
- Repeating
- Only with a count far above the band, after four to six weeks, to see whether it persists. Otherwise it comes along with every blood count by itself.
- Which test
- Basophils is in the comprehensive test (€229) and in .
- Where to draw
- You can draw at 250+ locations near you, no referral needed. See the locations
Frequently asked questions
What are basophils?
The rarest white blood cells, fewer than one in a hundred. Their granules are full of histamine and heparin. In an allergic reaction they recognise the allergen through antibodies on their surface and release the histamine that widens the vessels, makes the nose run and the skin itch. They are the travelling relatives of the mast cells in the tissue.
What is a normal basophil value?
Between 0 and 0.15 ×10⁹/L, where the labs overlap. All labs start at zero, so zero is just as healthy as any other number in the band. Because there are so few, the lab counts only a handful in an ordinary measurement, and the difference between zero and a few hundredths is measurement noise.
What does a high basophil count mean?
Usually a mild response, and the other white cells say to what. With high eosinophils and a normal CRP it is an allergy. With high monocytes and a high CRP it is an inflammation that has been running a while. With a high TSH it is an underactive thyroid. A count that repeatedly stays far above the band, with a strongly raised total of white cells and immature cells, is the picture of a bone marrow disease and is assessed the same day.
What does a low basophil count mean?
Nothing. All labs start their band at zero, cortisol and prednisone suppress the count with stress, illness and an acute allergic reaction, and an ordinary measurement counts only a handful anyway. There is no lower limit that points to a deficiency or a condition.
Why do basophils say something only in the pattern?
Because they are so scarce that an ordinary measurement can hardly tell normal from slightly raised, and because with allergy and inflammation they track cells that play the lead. Eosinophils carry the allergy, monocytes and CRP the inflammation. Basophils confirm what those already say, and only in a bone marrow disease do they stand at the front themselves.
How do I bring my basophils down?
By tackling the reason, not the cell. Anyone who treats their hay fever, asthma or eczema sees eosinophils and basophils fall together. Anyone who tackles an inflammation in the gut, the joints or the gums sees them fall along with CRP. An underactive thyroid that is treated brings the count back. A mild rise on its own asks for nothing.
What is the difference between basophils and eosinophils?
Both take part in allergy, but with a different role. Eosinophils are ten times as many and attack parasites and, in allergy, the body's own tissues with toxic proteins. Basophils release histamine, the substance that gives the acute reaction: the running nose, the itch, the swelling. In an allergy the eosinophils lead and the basophils rise slightly along.
When is a high count a reason for investigation?
When it repeatedly stays far above the band and the total of white cells is strongly raised, with immature cells on the report. That is the picture of chronic myeloid leukaemia, a bone marrow disease in which the production of white cells goes astray, and in which persistently high basophils are one of the first signs. The lab sees that picture and passes it on the same day. It is rare, and it is very treatable.
Which tests include basophils?
Basophils is in the Biological age test (€69, also as an add-on for €15), in the comprehensive test (€229) and in .
Related biomarkers
Sources
- 1.Unilabs, test catalogue (Dutch): white cell differential. 2026. bepalingenklapper.nl
- 2.Star-shl, test catalogue (Dutch): basophils. 2026. star-shl.nl
- 3.Certe, test catalogue (Dutch): basophil granulocytes. 2026. bepalingenwijzer.certe.nl
- 4.LESA Laboratory diagnostics (Dutch primary-care laboratory agreement). 2026. richtlijnen.nhg.org
Educational information only, not medical advice. Consult a healthcare professional for clinical decisions.
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