WBC; WCC; leukocyte count; white count
If your doctor thinks that you might have an infection or allergy and to monitor treatment
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
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.
The blood sample is obtained by a needle placed in a vein in the arm or by a fingerprick or heelprick (for newborns).
No test preparation is needed.
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.
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.
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.
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.
Treatment depends upon the cause. Infections usually cause increased WBC counts and may be treated with antibiotics. Leukaemias require chemotherapy and other treatments.
Full blood count; Blood film, Differential -white blood cells
RCPA Manual: White cell count
MedlinePlus: WBC count
Last Review Date: March 16, 2017