White Blood Cell Count
Written by Ada’s Medical Knowledge Team
What is a white blood cell (WBC) count?
Our blood contains a certain white blood cell count (WBC, leukocytes or leucocytes) which, as part of the body’s immune system, help the body fight infection. 1 A white blood cell (WBC) count measures the amount of white blood cells in a sample of a person’s blood. The number of white blood cells in the body differs between individuals or at different ages in their lives. The normal white blood cell count in a healthy adult is between 4,000 and 11,000 WBCs per microliter (μl or mcL) or cubic millimeter (mm3) of blood, though this may differ between males and females, and healthy children and young people usually have more.
To measure the number of white blood cells in a person’s body, a doctor will order a white blood cell count, often as part of a complete blood count (CBC) test. A low white blood cell count can indicate conditions including infections, inflammation, certain cancers, HIV/AIDS, and others, making it an important diagnostic test. Aside from these conditions, a person’s white blood cell count can indicate their immune system activity, response to cancer treatment and overall health.
White blood cells (WBCs)
There are several kinds of white blood cells (WBCs), including neutrophils, eosinophils, lymphocytes, monocytes and basophils. Each variety plays a different role in protecting the body from foreign pathogens such as viruses, bacteria, fungi and parasites. White blood cells also defend the body from allergens, mutated cells, such as cancer, and foreign matter, such as splinters, and remove dead cells, old red blood cells and other debris. 1
A white blood cell count checks both the overall levels of white blood cells in the blood, as well as the overall proportion of different types of white blood cells.
Low white blood cell count
The threshold for a low white blood cell count (leukopenia) varies between individuals and cases, but is generally considered to be anything lower than 4,000 white blood cells per μl of blood in an adult. A low white blood cell count can be caused by issues including: 2
- Viral or bacterial infection
- Diminished bone marrow function
- Autoimmune disorders including rheumatoid arthritis and HIV/AIDS
- Cancer treatment such as radiation and chemotherapy, as well as other medications
- Aplastic anemia
A low white blood cell count may cause symptoms such as fever, chills, headache and bodyache.
If you are experiencing symptoms that may be related to a low white blood cell count or one of the underlying conditions associated with it, begin your personal health assessment with the Ada app now.
High white blood cell (WBC) count
Though it varies between individuals, a high white blood cell count (leukocytosis) is usually considered to be anything above 11,000 cells per μl of blood in an adult. This can be related to: 3
- Bone marrow disease
- Autoimmune disorders such as rheumatoid arthritis
- Whooping cough
- Smoking 4
In most instances, there are no specific symptoms related to an elevated white blood cell count, though symptoms associated with the underlying medical condition may occur. However, in extreme cases, such as when leukocytosis occurs because of a condition affecting the bone marrow, symptoms directly related to an elevated white blood cell count may occur.
If you are experiencing symptoms that may be related to a high white blood cell count or one of the underlying conditions associated with it, begin your personal health assessment with the Ada app now.
High white blood cell count during pregnancy
Typically, white blood cell count is elevated during pregnancy, with the lower limit of the reference range being around 6,000 cells per μl and the upper limit around 17,000 cells per μl. 5 The stress imposed on the body through pregnancy causes this rise in white blood cells. 6
During delivery and in the hours that follow, the white blood cell count range can be anywhere between 9,000 and 25,000 white blood cells per μl of blood. The white blood cell count will typically return to normal around four-weeks after delivery. 6
Normal white blood cell count
A normal white blood cell count is a reading that falls within a range established through the testing of men, women and children of all ages. Although it is possible to cite general values, exact ranges tend to differ between labs and countries.
For men, a normal white blood cell count is anywhere between 5,000 and 10,000 white blood cells per μl of blood. For women, it is a reading of between 4,500 and 11,000 per μl, and for children between 5,000 and 10,000. 7 Not all sources, however, differentiate between male and female values; of these sources, values for both sexes tend to lie in the range between 4,000 to 4,500 and 10,000 to 11,000 cells per μl. 8
To carry out a white blood cell count, a doctor will draw a blood sample, usually from a vein in the arm or the back of the hand. This is a common procedure, and side effects are rare, but may include lightheadedness, bleeding or infection. No special preparation is required for a white blood cell count, but a person should inform their doctor of any medications they are taking, as these can affect the results. A white blood cell count is usually taken as part of a complete blood count.
Read more about a complete blood count »
White blood cell count FAQs
Q: What is a healthy white blood cell (WBC) count?
A: For an adult, a healthy WBC count is considered to be between 4,000 and 11,000 WBCs per microliter of blood. This is on average – some healthy individuals may have a higher or lower count.
Q: What is leukocytosis?
A: Leukocytosis is the condition of having an abnormally high WBC count. In most cases, an elevated WBC count will result in no symptoms, though symptoms associated with the underlying condition causing the high WBC count may occur. In extreme cases, such as when leukocytosis occurs because of a bone marrow disorder, symptoms directly related to an elevated WBC count may occur. Feeling unwell? Get a free symptom assessment with the Ada app.
Q: What is hematology?
A: Hematology (alternatively spelled haematology) is the branch of medicine concerned with blood and the various disorders and conditions involving blood. This includes the study of problems with white blood cells (WBCs), red blood cells (RBCs), bone marrow and platelets, which may include conditions such as anemia, leukemia, myeloproliferative disorders and neutropenia. 4
Q: Are there any types of cancer associated with white blood cells (WBCs)?
A: Yes, there are two main types of cancer associated with WBCs: leukemia and lymphoma. Leukemia is a cancer found in the blood and bone marrow which is caused by the rapid production of abnormal WBCs. These abnormal cells impair the body’s ability to fight infection, as well as the ability of bone marrow to produce platelets and red blood cells. 9 There are four main types of leukemia: acute myeloid, chronic myeloid, acute lymphocytic and chronic lymphocytic. Lymphoma, the second type of cancer involving WBCs, occurs when lymphocytes (small leukocytes that are part of the immune system) behave abnormally and collect in certain areas of the body. Lymphocytes can collect anywhere in the body, most commonly in the lymph nodes in the neck, armpits and groin. 10 Treatment options are available for both types of cancer.
Q: What is the relationship between bone marrow and white blood cells (WBCs)?
A: Bone marrow is the soft tissue inside the bones. It contains stem cells which can develop into WBCs, RBCs and platelets. 10
“Health Library: Facts About Blood.” Johns Hopkins Medicine. Accessed: 16 September, 2017.
“Low White Blood Cell Count.” Mayo Clinic. Accessed: 16 September, 2017.
“High White Blood Cell Count.” Mayo Clinic. Accessed: 16 September, 2017.
“Blood Disorders.” American Society of Hematolog. Accessed: 3 May, 2018.
NCBI. “Pregnancy and laboratory studies: a reference table for clinicians.” December 2009. Accessed August 6, 2018.
NCBI. “Physiological Changes in Hematological Parameters During Pregnancy.” July 15, 2012. Accessed July 25, 2018.
Leukemia & Lymphoma Society. “Understanding Blood Counts.” Accessed July 25, 2018.
Medscape. “Leukocyte Count (WBC).” September 15, 2015.
“Blood Cancers.” American Society of Hematology. Accessed: 3 May, 2018.
“Bone Marrow Diseases.” Medline Plus. Accessed: May 3, 2018.