At a glance

Also known as

WBC; WCC; leukocyte count; white count

Why get tested?

If your doctor thinks that you might have an infection or allergy and to monitor treatment

When to get tested?

As part of a full blood count (FBC), which may be used for a variety of reasons

Sample required?

A blood sample drawn from a vein in your arm or by a fingerprick or heelprick

Test preparation needed?

None

What is being tested?

The white blood cell (WBC) count indicates the number of white blood cells in a sample of blood. This count provides a clue to the presence of illness. White blood cells are made in the bone marrow and protect the body against infection and aid in the immune response. If an infection develops, white blood cells attack and destroy the bacteria causing the infection.

How is the sample collected for testing?

The blood sample is obtained by a needle placed in a vein in the arm or by a fingerprick or heelprick (for newborns).

Is any test preparation needed to ensure the quality of the sample?

No test preparation is needed.

The Test

How is it used?

Conditions or drugs that weaken the immune system, such as HIV infection or chemotherapy, cause a decrease in white blood cells. The WBC count detects dangerously low numbers of these cells.

The WBC count is used to suggest the presence of an infection, an allergy, or leukaemia. It is also used to help monitor the body’s response to various treatments and to monitor bone marrow function.

When is it requested?

A WBC count is normally ordered as part of the full blood count (FBC), which is requested for a wide variety of reasons. A WBC count also may be used to monitor recovery from illness. Counts that continue to rise or fall to abnormal levels may indicate that the condition is getting worse. Counts that return to normal indicate improvement.

What does the test result mean?

An elevated number of white blood cells is called leukocytosis. This can result from bacterial infections, inflammation, leukaemia, trauma or stress. A WBC count of 11.0 – 17.0 x 109/L cells would be considered mild to moderate leukocytosis.

A decreased WBC count is called leukopenia. It can result from many different situations, such as chemotherapy, radiation therapy or diseases of the immune system. A count of 3.0 – 3.5 x 109/L cells would be considered mild leukopenia.

Is there anything else I should know?

Eating, physical activity and stress can cause an increased WBC count.

Pregnancy in the final month and labour may be associated with increased WBC levels.

If you have had your spleen removed, you may have a persistent mild to moderate increased WBC count.

The WBC count tends to be lower in the morning and higher in the late afternoon. WBC counts are age-related.

On average, normal newborns and infants have higher WBC counts than adults. It is not uncommon for the elderly to fail to develop leukocytosis as a response to infection.

There are many drugs that cause both increased and decreased WBC counts.

Common Questions

Are there different types of WBCs?

Yes. There are five main types: neutrophils, lymphocytes, monocytes, eosinophils, and basophils.

How do you treat abnormal WBC levels?

Treatment depends upon the cause. Infections usually cause increased WBC counts and may be treated with antibiotics. Leukaemias require chemotherapy and other treatments.