What Are Basophils in a Blood Test? Normal Range & High Levels
Also known as: Absolute basophils, baso blood test, basophil count
Basophils are the least common type of white blood cell, involved in allergic reactions and inflammation by releasing histamine. They're counted on a complete blood count (CBC) with differential. A normal absolute basophil count is roughly 0–200 cells per microliter (0–1% of white blood cells); a high count can accompany allergies or, rarely, certain bone-marrow disorders.
Basophils normal range
| Category | Range (cells/µL) |
|---|---|
| Normal (absolute) | 0–200 cells/µL |
| Normal (percentage) | 0–1% of WBCs |
| Elevated (basophilia) | > 200 cells/µL |
Reference ranges vary by laboratory. Use the range printed on your own report as the definitive comparison.
What high Basophils can mean
- Allergic reactions
- Chronic inflammation
- Underactive thyroid (hypothyroidism)
- Rarely, myeloproliferative disorders such as chronic myeloid leukemia
What low Basophils can mean
- Low basophils are usually not significant
- Can occur with acute infection, stress, or steroid use
What to do about an abnormal result
- A mildly high basophil count is common and usually not concerning on its own.
- Persistent basophilia with other abnormal blood counts may prompt further evaluation.
- Always interpret with the full CBC and differential.
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Frequently asked questions
What does a high basophil count mean?
A high basophil count (basophilia) is most often linked to allergies, chronic inflammation, or an underactive thyroid. Rarely, persistently high basophils alongside other abnormal blood counts can signal a bone-marrow disorder, which is why the whole CBC is reviewed together.
Should I worry about a slightly elevated basophil percentage?
Usually not. Basophils are the rarest white blood cell, so small changes in the percentage are common and typically harmless, especially when the rest of your CBC is normal.
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Medically reviewed by Antonieta Rueda, MD and Ayham Shneker, MD · Last reviewed July 6, 2026
This article is for informational and educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition or your lab results.