At a Glance
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
A blood sample drawn from a vein in your arm or by a fingerprick or heelprick
Test Preparation Needed?
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 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.
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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.