A blood test can reveal a lot about your health, and the white blood cell (WBC) count is a key indicator. It’s often listed among the results as “WBC” and can help healthcare providers understand what’s happening inside your body. The WBC count test is used to monitor chronic health conditions and evaluate your response to treatment.
This article will delve into the details of the WBC count test, explaining the different types of WBCs and their functions, and what constitutes a normal WBC count by age.
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What is a WBC Test?
A WBC count test is a blood test that determines the number and types of white blood cells in your blood.
White blood cells are a crucial part of your immune system. Their main role is to fight infection and inflammation. They also protect your body from toxins and assist in wound healing and tissue repair. White blood cells are produced in the bone marrow. Despite making up less than 1% of your total blood cells, they are essential for maintaining good health.
The WBC count test is a simple blood draw. A healthcare professional uses a thin needle to take a blood sample from a vein, typically in your arm. You can expect to receive the test results from the lab within a few days. No special preparation is needed; you don’t have to fast, and the test can be done at any time of day.
What It Measures: Types of White Blood Cells
A WBC count measures the total number of white blood cells in your blood. There are five main types, each with a specific function:
- Neutrophils: These are the most abundant type, usually making up 50-75% of all WBCs. They primarily fight bacterial and fungal infections.
- Lymphocytes: These cells fight infections, produce antibodies, and attack tumors. They are found in both the blood and lymph tissues.
- Monocytes: Monocytes remove damaged or dead cells from the body. They can also travel into tissues like the lungs and liver and transform into other cell types that help reduce inflammation.
- Eosinophils: These cells primarily combat parasitic infections and respond to allergic reactions and inflammation.
- Basophils: During an allergic response, basophils release histamine, a chemical that triggers symptoms such as a runny nose or watery eyes.
If your healthcare provider orders a WBC differential test, you will see these five cell types listed on your results along with numeric values. This “diff” test analyzes each cell type to determine the underlying cause of an abnormal WBC count. This helps to identify potential issues.
WBC counts are frequently performed as part of a more comprehensive test known as a complete blood count (CBC). In addition to WBCs, the CBC also assesses red blood cells (which carry oxygen throughout the body) and platelets (which are essential for blood clotting). The CBC is a standard test for evaluating overall health and detecting various illnesses, including anemia, infections, and leukemia.
Normal WBC Count by Age
It’s important to note that a “normal” WBC count isn’t a fixed number and can vary from person to person. Factors such as age, sex, race, and smoking status can influence what’s considered normal for you. WBC counts are typically high at birth, gradually decreasing through infancy and then slowly declining until adulthood. They are measured as the number of white blood cells per cubic millimeter of blood (cells/mm3).
Here are the typical normal WBC count ranges by age:
- Babies 0 to 2 weeks old: 9,000 to 30,000 cells/mm3
- Babies 2 to 8 weeks old: 5,000 to 21,000 cells/mm3
- Children 2 months to 6 years old: 5,000 to 19,000 cells/mm3
- Children 6 to 18 years old: 4,800 to 10,800 cells/mm3
- Adults: 4,500 to 11,000 cells/mm3
Results within these ranges are considered normal. Values below these ranges are considered low, and those above are considered high. However, individual variations exist, and WBC counts can fluctuate throughout the day. Additionally, normal WBC ranges can vary between different labs, so it’s recommended to use the same lab provider for ongoing blood tests.
Understanding Normal WBC Levels for Women
The normal WBC count range for women is often slightly wider than that for men. A normal WBC for women can range from 4,500 to 11,000 cells/mm3, while the typical range for men is between 5,000 and 10,000 cells/mm3.
What Does a High WBC Mean?
An elevated WBC count is called leukocytosis. It indicates that something may be happening in the body. Possible causes of leukocytosis include:
- Bacterial, fungal, or parasitic infection
- Inflammatory conditions
- Burns
- Corticosteroid use
- Cigarette smoking
- Pregnancy
- Leukemia
What Does a Low WBC Mean?
A low WBC count is known as leukopenia. While a low count on its own may not be cause for alarm, potential causes of leukopenia include:
- Blood or bone marrow disorder
- Autoimmune disorders
- Medication side effects
- Chemotherapy or radiation therapy
- Viral infection
It’s crucial to avoid jumping to conclusions based solely on a high or low notation on your WBC count results. The test needs to be interpreted in conjunction with other blood test values and possibly further testing to determine the underlying cause.
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Medications Can Cause Abnormal WBC Counts
Many prescription and over-the-counter medications can affect your WBC count. Therefore, it’s essential to discuss your medication history with your healthcare provider.
Certain drugs can decrease your WBC count, including:
- Antibiotics: Used to treat bacterial infections.
- Anticonvulsive drugs: Used to treat epilepsy and chronic pain.
- Chemotherapy: Used to treat cancer.
- Rituxan (rituximab): Used to treat autoimmune diseases and certain cancers.
Other medications can increase your WBC count. Some of the more common ones include:
When to See Your Healthcare Provider
Consider consulting your healthcare provider if you experience symptoms that suggest your WBC count may be abnormal, such as:
- Fever
- Body aches
- Chills
- Night sweats
- Persistent or severe fatigue
- Swollen lymph nodes
- Allergy symptoms
If you exhibit these symptoms, your healthcare provider may order a WBC count test.
Further Testing
If your WBC count results are abnormal, your healthcare provider may order further tests based on your symptoms and medical history. These tests might include:
Summary
White blood cells are essential for fighting infection and inflammation. A white blood cell count test measures the number of white blood cells in a blood sample. Numerous conditions, including infections, medications, inflammatory diseases, and blood or bone marrow disorders, can lead to an abnormal WBC count.
The WBC count is measured against a reference range, expressed as the number of blood cells in a cubic millimeter of blood. Test results can vary depending on the lab and its definition of low, normal, or high ranges.
Normal WBC counts vary with age, starting high at birth and decreasing through childhood. The normal range also differs by sex and can fluctuate throughout the day.
While a WBC count is not specific enough to diagnose a particular disease or condition, it can provide valuable insights into the potential causes of your symptoms.
