White Blood Cell Count

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Also known as: WBC; Leucocyte count; White count
Related tests: Full blood count

At a Glance

Why Get Tested?

If your doctor thinks that you might have an infection, inflammatory illness, immune deficiency, bone marrow disease or allergy and; to monitor treatment

When to Get Tested?

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

Sample Required?

A blood sample taken from a vein in your arm or from a finger-prick or in babies a heelprick

Test Preparation Needed?

None

The Test Sample

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 micro-organism 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 from a finger-prick or heel-prick (for newborns).

NOTE: If undergoing medical tests makes you or someone you care for anxious, embarrassed, or even difficult to manage, you might consider reading one or more of the following articles: Coping with Test Pain, Discomfort, and Anxiety, Tips on Blood Testing, Tips to Help Children through Their Medical Tests, and Tips to Help the Elderly through Their Medical Tests.

Another article, Follow That Sample, provides a glimpse at the collection and processing of a blood sample and throat culture.

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

No test preparation is needed.

The Test

Common Questions

Ask a Laboratory Scientist

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NOTE: This article is based on research that utilizes the sources cited here as well as the collective experience of the Lab Tests Online Editorial Review Board. This article is periodically reviewed by the Editorial Board and may be updated as a result of the review. Any new sources cited will be added to the list and distinguished from the original sources used.