Also Known As
Leucocyte count
White count
Formal Name
White Blood Cell Count
This article was last reviewed on
This article waslast modified on 24 July 2018.
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?


On average it takes 7 working days for the blood test results to come back from the hospital, depending on the exact tests requested. Some specialist test results may take longer, if samples have to be sent to a reference (specialist) laboratory. The X-ray & scan results may take longer. If you are registered to use the online services of your local practice, you may be able to access your results online. Your GP practice will be able to provide specific details.

If the doctor wants to see you about the result(s), you will be offered an appointment. If you are concerned about your test results, you will need to arrange an appointment with your doctor so that all relevant information including age, ethnicity, health history, signs and symptoms, laboratory and other procedures (radiology, endoscopy, etc.), can be considered.

Lab Tests Online-UK is an educational website designed to provide patients and carers with information on laboratory tests used in medical care. We are not a laboratory and are unable to comment on an individual's health and treatment.

Reference ranges are dependent on many factors, including patient age, sex, sample population, and test method, and numeric test results can have different meanings in different laboratories.

For these reasons, you will not find reference ranges for the majority of tests described on this web site. The lab report containing your test results should include the relevant reference range for your test(s). Please consult your doctor or the laboratory that performed the test(s) to obtain the reference range if you do not have the lab report.

For more information on reference ranges, please read Reference Ranges and What They Mean.

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).

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

No test preparation is needed.

Accordion Title
Common Questions
  • 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 bone marrow disorder. It is also used to help monitor the body's response to various treatments.

  • When is it requested?

    A WBC count is part of the full blood count (FBC), which is requested for a variety of reasons. Changes in the WBC, whether it is high or low, may indicate a worsening or improvement in a medical condition.

  • What does the test result mean?

    An elevated number of white blood cells is called leucocytosis. This can result from bacterial infections, inflammation, leukaemia and other blood disorders, trauma, medication, or post-operatively. A WBC count of 11.0–17.0x109/L cells would be considered mild to moderate leucocytosis.  

    A decreased WBC count is called leucopenia. It can result from many different situations, such as

    • medication, especially chemotherapy, or radiotherapy
    • bone marrow disorder
    • vitamin deficiency, such as B12 or folic acid
    • liver disease
    • an enlarged spleen
    • occasionally in inflammatory conditions such as rheumatoid arthritis or SLE
    • some infections (particularly viral infections)
    • diseases of the immune system

     A count of 3.0–4.0x109/L cells would be considered mild leucopenia.

  • Is there anything else I should know?

    Increased WBC levels may be seen during the late stages of pregnancy.

    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 change with age with normal newborns and infants typically have a higher WBC counts than adults. It is not uncommon for the elderly to fail to develop leucocytosis (a high WBC) as a response to infection.

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

  • 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 many causes, and is not always required. Bacterial infections usually cause increased WBC counts and may be treated with antibiotics.

    Leukaemias and other bone marrow disorders may require chemotherapy and other treatments.

    Low WBC counts may also require treatment. Severely low WBC counts putting patients at risk of infection (for example after chemotherapy) may require treatment with growth factor injections (GCSF), usually given under the skin.