Maybe you've recently had a complete blood count (CBC) done. This test checks the levels of red blood cells, white blood cells and platelets. People who have a CBC often find out that they have a high white blood cell count. Your doctor might use the term leukocytosis. It means the same thing - that your white blood cell count is higher than normal.
Leukocytosis is usually the result of the body's response to infection or inflammation. In some cases, though, it may have more serious causes, including leukemia. To understand leukocytosis, it helps to understand more about white blood cells and what they do.
White blood cells: the leukocytes
White blood cells, or leukocytes, are part of the immune system. Their main job is to fight infection. Most are produced in the bone marrow. They travel through the bloodstream, patrolling for bacteria, viruses and other harmful organisms.
There are five basic types of white blood cells: neutrophils, eosinophils, basophils, lymphocytes and monocytes. Each has a different way of defending the body against infection. Some make antibodies, some surround and consume germs and others are involved in wound healing.
Normally only a small percentage of white blood cells circulate through the blood. Most stay in the bone marrow. When germs get into the body, the white blood cells pour out of the bone marrow and rush to the site of infection or injury. This causes a spike in the white blood cell count.
What is an abnormal white blood cell count?
A normal white blood cell count in adults is about 5,000 to 10,000 white blood cells per microliter of blood. A high white blood cell count (leukocytosis) is usually defined as 11,000 or more white blood cells per mL of blood.
A complete blood count includes a count of each type of white blood cell. The most common cause of a high white blood cell count is an increase in neutrophils. This is called neutrophilia or neutrophilic leukocytosis. Which cell type is most elevated can give clues to what is causing the abnormal reading.
What can cause a high white blood cell count?
There are many possible reasons for an elevated white blood cell count, including:
- Infection such sinusitis or bladder infection
- Inflammation due to a burn, skin rash or other tissue damage
- Allergic reaction
- Rheumatoid arthritis
- Physical or emotional stress
- Smoking
- Pregnancy
- Medications such as corticosteroids, lithium and epinephrine
- Inflammatory bowel disease
- Hemolytic anemia, which includes sickle cell anemia
- Surgery to remove the spleen
- Cancer of the blood or bone marrow, such as leukemia
- Hodgkin's disease and non-Hodgkin's lymphoma
More testing may be needed to find the exact cause of a high white blood cell count.
