Also Known As
WBC Count
Leukocyte Count
White Count
This article was last reviewed on
This article waslast modified on September 19, 2019.
At a Glance
Why Get Tested?

To screen for or diagnose a variety of conditions that can affect the number of white blood cells (WBCs), such as an infection, inflammation or a disease that affects WBCs; to monitor treatment of a disorder or to monitor therapy that is known to affect WBCs

When To Get Tested?

As part of a complete blood count (CBC), when you have a routine health examination; when you have signs and symptoms that may be related to a condition affecting the number of WBCs; when you have a condition or are receiving treatment that is known to affect WBCs

Sample Required?

A blood sample drawn from a vein or by a fingerstick (children and adults) or heelstick (newborns)

Test Preparation Needed?

None

What is being tested?

White blood cells, also called leukocytes, are cells that exist in the blood, the lymphatic system, and tissues and are an important part of the body's defense system. They help protect against infections and also have a role in inflammation, and allergic reactions. The white blood cell (WBC) count totals the number of white blood cells in a sample of your blood. It is one test among several that is included in a complete blood count (CBC), which is often used in the general evaluation of your health.

Blood is made up of three main types of cells suspended in fluid called plasma. In addition to WBCs, there are red blood cells and platelets. All of these cells are made in the bone marrow and are released into the blood to circulate.

There are five types of WBCs, and each has a different function:

  • Three types of WBCs are referred to as "granulocytes" because of the granules present in their cytoplasm. These granules release chemicals and other substances as part of the immune response. Granulocytes include:
    • Neutrophils (neu) normally make up the largest number of circulating WBCs. They move into an area of damaged or infected tissue, where they engulf and destroy bacteria or sometimes fungi.
    • Eosinophils (eos) respond to infections caused by parasites, play a role in allergic reactions (hypersensitivities), and control the extent of immune responses and inflammation.
    • Basophils (baso) usually make up the fewest number of circulating WBCs and are thought to be involved in allergic reactions.
  • Lymphocytes (lymphs) exist in both the blood and the lymphatic system. They are divided into three types:
    • B lymphocytes (B cells) produce antibodies as part of the body’s natural defense (immune) responses.
    • T lymphocytes (T cells) recognize foreign substances and process them for removal.
    • Natural killer cells (NK cells) directly attack and kill abnormal cells such as cancer cells or those infected with a virus.
  • Monocytes (mono), similar to neutrophils, move to an area of infection and engulf and destroy bacteria. They are associated more often with chronic rather than acute infections.

When there is an infection or an inflammatory process somewhere in the body, the bone marrow produces more WBCs, releasing them into the blood, and through a complex process, they move to the site of infection or inflammation. As the condition resolves, the production of WBCs by the bone marrow subsides and the number of WBCs drops to normal levels again.

In addition to infections and inflammation, there are a number of conditions that can affect the production of WBCs by the bone marrow or the survival of WBCs in the blood, such as cancer or an immune disorder, resulting in either increased or decreased numbers of WBCs in the blood. The WBC count, along with the other components of the CBC, alerts a healthcare practitioner to possible health issues. Results are often interpreted in conjunction with additional tests, such as a WBC differential and a blood smear review. A differential may provide information on which type of WBC may be low or high, and a blood smear may show the presence of abnormal and/or immature WBCs.

If results indicate a problem, a wide variety of other tests can be performed to help determine the cause. A healthcare practitioner will typically consider an individual's signs and symptoms, medical history, and results of a physical examination to decide what other tests may be necessary. For example, as needed, a bone marrow biopsy will be performed to evaluate the bone marrow status.

You may be able to find your test results on your laboratory's website or patient portal. However, you are currently at Lab Tests Online. You may have been directed here by your lab's website in order to provide you with background information about the test(s) you had performed. You will need to return to your lab's website or portal, or contact your healthcare practitioner in order to obtain your test results.

Lab Tests Online is an award-winning patient education website offering information on laboratory tests. The content on the site, which has been reviewed by laboratory scientists and other medical professionals, provides general explanations of what results might mean for each test listed on the site, such as what a high or low value might suggest to your healthcare practitioner about your health or medical condition.

The reference ranges for your tests can be found on your laboratory report. They are typically found to the right of your results.

If you do not have your lab report, consult your healthcare provider or the laboratory that performed the test(s) to obtain the reference range.

Laboratory test results are not meaningful by themselves. Their meaning comes from comparison to reference ranges. Reference ranges are the values expected for a healthy person. They are sometimes called "normal" values. By comparing your test results with reference values, you and your healthcare provider can see if any of your test results fall outside the range of expected values. Values that are outside expected ranges can provide clues to help identify possible conditions or diseases.

While accuracy of laboratory testing has significantly evolved over the past few decades, some lab-to-lab variability can occur due to differences in testing equipment, chemical reagents, and techniques. This is a reason why so few reference ranges are provided on this site. It is important to know that you must use the range supplied by the laboratory that performed your test to evaluate whether your results are "within normal limits."

For more information, please read the article Reference Ranges and What They Mean.

White Blood Cell Count Reference Range

The reference ranges1 provided here represent a theoretical guideline that should not be used to interpret your test results. Some variation is likely between these numbers and the reference range reported by the lab that ran your test. Please consult your healthcare provider.

Age Conventional Units2 SI Units3
0-18 years Not available due to wide variability. See child's lab report for reference range.
Adult 4,500-11,000 white blood cells per microliter (mcL) 4.5-11.0 x 109 per liter (L)

1 from Wintrobe's Clinical Hematology. 12th ed. Greer J, Foerster J, Rodgers G, Paraskevas F, Glader B, Arber D, Means R, eds. Philadelphia, PA: Lippincott Williams & Wilkins: 2009.

2 Conventional Units are typically used for reporting results in U.S. labs

3 SI Units are used to report lab results outside of the U.S.

Accordion Title
Common Questions
Health Professionals – LOINC

Logo for LOINC from RegenstriefLOINC Observation Identifiers Names and Codes (LOINC®) is the international standard for identifying health measurements, observations, and documents. It provides a common language to unambiguously identify things you can measure or observe that enables the exchange and aggregation of clinical results for care delivery, outcomes management, and research. Learn More.

Listed in the table below are the LOINC with links to the LOINC detail pages.

LOINC LOINC Display Name
26464-8 WBC (Bld) [#/Vol]
6690-2 WBC Auto (Bld) [#/Vol]
49498-9 WBC Estimate (Bld) [#/Vol]
804-5 WBC Manual cnt (Bld) [#/Vol]
View Sources

Sources Used in Current Review

2019 review performed by Michelle Moy, M.Ad.Ed, MT (ASCP) SC, Program Director and Assistant Professor, Medical Laboratory Science/Biomedical Science Madonna University.

(December 15, 2014) Lewicki, et al. The influence of vitamin B12 supplementation on the level of white blood cells and lymphocytes phenotype in rats fed a low-protein diet Available online at https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4439950/. Accessed on July 8, 2019.

American Society for Hematology. Blood Basics for Patients. Available online at https://www.hematology.org/Patients/Basics/. Accessed on July 8, 2019.

(2013) Balkaransingh. Dietary Determinants Of The White Blood Cell Count. American Society for Hematology Blood Journal. Available online at http://www.bloodjournal.org/content/122/21/1705?sso-checked=true. Accessed on July 8, 2019.

Elaine M. Keohane PhD MLS(ASCP)SHCM (Author), Catherine N. Otto PhD MBA MLS(ASCP)CM SH DLM (Author), Jeanine M. Walenga PhD MLS(ASCP)HCM (Author) Rodak's Hematology: Clinical Principles and Applications Elsevier/Saunders; 6 edition (March 11, 2019) pp 117-135.

Sources Used in Previous Reviews

Thomas, Clayton L., Editor (1997). Taber's Cyclopedic Medical Dictionary. F.A. Davis Company, Philadelphia, PA [18th Edition].

Pagana, Kathleen D. & Pagana, Timothy J. (2001). Mosby's Diagnostic and Laboratory Test Reference 5th Edition: Mosby, Inc., Saint Louis, MO.

Susan J. Leclair, PhD, CLS(NCA). Professor of Medical Laboratory Science, Department of Medical Laboratory Science, University of Massachusetts, Dartmouth, MA.

Pagana, Kathleen D. & Pagana, Timothy J. (© 2007). Mosby's Diagnostic and Laboratory Test Reference 8th Edition: Mosby, Inc., Saint Louis, MO. Pp 1003-1008.

Harmening D. Clinical Hematology and Fundamentals of Hemostasis, Fifth Edition, F.A. Davis Company, Philadelphia, 2009, Pp 305-328.

Henry's Clinical Diagnosis and Management by Laboratory Methods. 21st ed. McPherson R, Pincus M, eds. Philadelphia, PA: Saunders Elsevier: 2007, Pp 543-549, 552-560.

Wintrobe's Clinical Hematology. 12th ed. Greer J, Foerster J, Rodgers G, Paraskevas F, Glader B, Arber D, Means R, eds. Philadelphia, PA: Lippincott Williams & Wilkins: 2009, Pp 1512-1516, 1522-1524.

(Updated May 10, 2010) Inoue S, et al. Leukocytosis, Medscape Reference article. Available online at http://emedicine.medscape.com/article/956278-overview. Accessed March 2012.

(Feb 1 2011) National Heart Lung Blood Institute. What is lymphocytopenia? Available online at http://www.nhlbi.nih.gov/health/health-topics/topics/lym/. Accessed March 2012.

(Jan 23 2012) American Cancer Society. Acute Lymphocytic Leukemia. Available online through http://www.cancer.org. Accessed March 2012.

(Dec 7 2010) American Cancer Society. Acute Myeloid Leukemia. Available online through http://www.cancer.org. Accessed March 2012.

(Oct 25 2010) American Cancer Society. Non-Hodgkin Lymphoma. Available online through http://www.cancer.org. Accessed March 2012.

(January 8 2010) Kempert P. White Blood Cell Function, Overview of the Immune System. Medscape Reference article. Available online at http://emedicine.medscape.com/article/960027-overview. Accessed March 2012.

(January 26, 2010) Naushad H. Leukocyte Count (WBC). Medscape Reference article. Available online at http://emedicine.medscape.com/article/2054452-overview#aw2aab6b2. Accessed March 2012.

Hsleh Matthew M, et al. Prevalence of neutropenia in the U.S. population: age, sex, smoking status, and ethnic differences. Annals of Internal Medicine. 2007;146:486-492.

Dugdale D. (2011 February 13 Updated). White blood cell count – series. MedlinePlus. Available online at http://www.nlm.nih.gov/medlineplus/ency/presentations/100151_1.htm. Accessed on 2/27/2015.

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Pagana, Kathleen D., Pagana, Timothy J., and Pagana, Theresa N. (© 2015). Mosby's Diagnostic and Laboratory Test Reference 12th Edition: Mosby, Inc., Saint Louis, MO. Pp 991-995.

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