Basophils Level in Blood Test: What It Reveals About Your Health

If you've noticed basophils on your blood test, you might have wondered what they mean. Let's explore what we know so far

Tania Sultana
By Tania Sultana
Caitlin Snethlage
Edited by Caitlin Snethlage

Published March 6, 2024.

A doctor taking a sample for testing basophils levels.

White blood cells (WBCs), or leukocytes, are the body's primary defense against infections, diseases, and abnormal cell growth.

Basophils are the least common type of WBCs, but they are essential in maintaining immune system health—protecting the body from allergens, pathogens, and parasites. There is still much that is unknown about them. [1] So, let's find out what they may reveal about your health.

What are basophils?

Basophils—comprising around 0.5% to 1% of circulating WBCs—were initially overlooked due to their scarcity compared to other immune cells. However, recent research has unveiled their diverse and crucial roles in the immune system, particularly in orchestrating inflammatory responses. [2]

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What are the functions of basophils?

These WBCs release signaling molecules called cytokines [3], which recruit and activate other immune cells, promote blood vessel permeability, and make delivering antibodies and nutrients to infection or injury sites easier.

Basophils' role in vascular integrity

Basophils contain the anticoagulant heparin, crucial in preventing blood clot formation. It binds to a protein called antithrombin III (AT). This link induces a conformational change in AT, which activates it significantly. [4]

Activated AT is a potent inhibitor of thrombin—factor IIa—and factor Xa, which cause the chain of reactions that lead to clot formation. [5] By inhibiting them, AT maintains vascular health and reduces the risk of complications like thrombosis.

» Understand the meaning of your cholesterol tests

Allergic reactions and basophils

Histamine is an inflammatory mediator, contributing significantly to the initiation and modulation of certain types of inflammatory responses. It increases blood flow, redness, and swelling, attracting immune cells to the site of infection or injury. 

The most common example of its effect is when an allergen—like pollen or dust mites—enters the body. Mast cells release histamine, causing symptoms like runny nose, itching, and sneezing as an attempt to remove the invader. [6]

Did you know?

Mast cells reside in skin, lung, and digestive tract tissues—surviving for months or even years. On the other hand, basophils circulate in the bloodstream and migrate to tissues during allergic reactions. They are short-lived, typically lasting only a few days. [7]

» Dive into regenerative medicine and immunology with Dr. Jennifer Elisseeff

What does the basophil count in a blood test mean?

While abnormal basophil levels often don't cause specific symptoms, they can sometimes indicate an underlying health condition. It's important to consult with a healthcare professional to determine the cause.

You can get two different counts in a test report:

  • Relative basophil count—measured as a percentage—provides information about the relative distribution of basophils within the white blood cell population but does not indicate their actual number in the blood.
  • Complete basophil count identifies how many are present in a blood sample.

Decreased basophil levels

Known as basopenia, decreased basophil levels are still a developing area of research. Possible causes include post-corticosteroid treatment, chronic urticaria, lupus, and diabetes. [2]

» Learn what low white blood cell count means

Elevated basophil levels

High basophil levels in a blood test—also known as basophilia—indicate a temporary or ongoing response to various triggers. Some common causes include:

  • An allergic reaction due to pollen, venom, or food
  • Parasitic infection
  • Inflammatory bowel disease
  • Collagen vascular disease, an autoimmune disorder
  • Polycythemia vera
  • Chronic myelogenous leukemia—a type of cancer in blood-forming cells of the bone marrow [8]

» Find out everything about high white blood cell count

What should you do If your basophil levels are elevated?

Because there is still so much we don't know about basophils, it's essential to take a holistic approach when interpreting the results.

While elevated levels can indicate an underlying issue, they're also quite common and often not a cause for immediate concern. Before making any diagnosis, lifestyle factors, blood biomarkers, and possible symptoms should be considered.

In most cases, elevated basophils are temporary and resolve on their own. Distinguishing between a short-term increase in basophils and a more serious underlying health issue typically involves a combination of factors, including a thorough medical history, physical examination, and additional diagnostic tests.

What lifestyle changes could help decrease elevated basophils?

While elevated basophils can sometimes cause allergic reactions, this is not always the case—other conditions can also cause similar symptoms. Consulting a healthcare professional for proper diagnosis and treatment is essential.

Food diaries and elimination diets can be helpful tools for identifying potential triggers under the guidance of a healthcare professional, but these methods shouldn't be used for self-diagnosis.

Note: If you suspect a clinical allergy, consulting with a healthcare professional like an allergist or immunologist is crucial. They can properly diagnose it, develop a personalized management plan, and recommend appropriate treatment.

» Discover the differences between food allergies, intolerances, and sensitivities

Basophils in blood: what's in store for the future?

By understanding how basophils contribute to inflammation, tissue damage, and tumor growth, researchers pave the way for more precise diagnoses, personalized therapies targeting these cells, and improved monitoring of disease progression. [9]

For instance, identifying unique markers on basophils could lead to earlier detection of autoimmune disorders, while modulating their activity might offer novel treatment options for allergies and even some cancers. [10]

InsideTracker's Ultimate Plan also dives deep into a range of biomarkers, including those essential for immune function. After purchasing, you can set your goal to "immunity" and get a personalized report with recommendations to improve your immune system based on your blood analysis.

InsideTracker doesn't diagnose or treat medical conditions. For any health-related concerns, consult your physician.


[1] M. C. Siracusa, B. S. Kim, J. M. Spergel, and D. Artis, “Basophils and allergic inflammation,” Journal of Allergy and Clinical Immunology, vol. 132, no. 4, pp. 789–801, 2013. doi:10.1016/j.jaci.2013.07.046

[2] H. Shah, S. Eisenbarth, C. A. Tormey, and A. J. Siddon, “Behind the scenes with basophils: An emerging therapeutic target,” Immunotherapy Advances, vol. 1, no. 1, 2021. doi:10.1093/immadv/ltab008

[3] G. A. Duque and A. Descoteaux, “Macrophage cytokines: involvement in immunity and infectious diseases,” Frontiers in Immunology, vol. 5, Oct. 2014, doi: 10.3389/fimmu.2014.00491.

[4] G. Izaguirre et al., “Conformational Activation of Antithrombin by Heparin Involves an Altered Exosite Interaction with Protease,” Journal of Biological Chemistry, vol. 289, no. 49, pp. 34049–34064, Dec. 2014, doi: 10.1074/jbc.m114.611707.

[5] E. A. Nutescu, A. Burnett, J. Fanikos, S. A. Spinler, and A. K. Wittkowsky, “Erratum to: Pharmacology of anticoagulants used in the treatment of venous thromboembolism,” Journal of Thrombosis and Thrombolysis, vol. 42, no. 2, pp. 296–311, May 2016, doi: 10.1007/s11239-016-1363-2.

[6] F. H. Falcone, D. Zillikens, and B. F. Gibbs, “The 21st Century renaissance of the basophil? current insights into its role in allergic responses and innate immunity,” Experimental Dermatology, vol. 15, no. 11, pp. 855–864, 2006. doi:10.1111/j.1600-0625.2006.00477.x

[7] S. Ducrest, F. A. Meier, C. Tschopp, R. Pavlovic, and C. A. Dahinden, “Flowcytometric analysis of basophil counts in human blood and inaccuracy of hematology analyzers,” Allergy, vol. 60, no. 11, pp. 1446–1450, Oct. 2005, doi: 10.1111/j.1398-9995.2005.00910.x.

[8] P. Valent et al., “Proposed diagnostic criteria and classification of basophilic leukemias and related disorders,” Leukemia, vol. 31, no. 4, pp. 788–797, Jan. 2017, doi: 10.1038/leu.2017.15.

[9] L. K. Oetjen, M. Noti, and B. Kim, “New insights into basophil heterogeneity,” Seminars in Immunopathology, vol. 38, no. 5, pp. 549–561, May 2016, doi: 10.1007/s00281-016-0567-z.

[10] K. Miyake, J. Ito, and H. Karasuyama, “Role of basophils in a broad spectrum of disorders,” Frontiers in Immunology, vol. 13, May 2022, doi: 10.3389/fimmu.2022.902494.