White Blood Cell Count
What is a white blood cell count?
Healthy blood contains a certain percentage of white blood cells (WBCs, leukocytes or leucocytes) which, as part of the body’s immune system, help the body fight infection. A white blood cell 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 range for a white blood cell count in a healthy adult is between 4,000 and 11,000 WBCs per microliter (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, 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
There are several kinds of white blood cells, 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.
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 microliter of blood in an adult. A low white blood cell count can be caused by issues including:
- 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.
High white blood cell count
Though it varies between individuals, a high white blood cell count (leukocytosis) is usually considered to be anything above 11,000 cells per microliter of blood in an adult. This can be related to:
- Bone marrow disease
- Autoimmune disorders such as rheumatoid arthritis
- Whooping cough
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.
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.
**Q: ** What is a healthy white blood cell count?
A: For an adult, a healthy white blood cell count is considered to be between 4,000 and 11,000 white blood cells per microliter of blood. This is on average, and some healthy individuals may have a higher or lower count.
“Vital Health and Statistics: Total White Blood Cell Counts for Persons Ages 1-74 Years With Differential Leukocyte Counts for Adults Ages 24-74 Years: United States 1971-75.” Centers for Disease Control and Prevention. Accessed: 16 September, 2017 ↩