Also Known As
Differential leucocyte count
Differential White Cell count
White blood cell morphology
WBC differential
Formal Name
White Blood Cell Differential
This article was last reviewed on
This article waslast modified on 6 July 2023.
At a Glance
Why Get Tested?

To diagnose an illness affecting your blood such as an infection, inflammatory illness, immune deficiency, or cancers such as leukaemia or lymphoma

When To Get Tested?

As part of a full blood count (FBC), which is a very common test that counts the different types of cells present in the blood and can identify or imply a large variety of diseases or disorders

Sample Required?

A blood sample taken from a vein in your arm or by a finger-prick (children and adults) or heel-prick (infants)

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?

There are five types of white blood cells, each with different functions: neutrophils, lymphocytes, monocytes, eosinophils and basophils. The differential reveals if these cells are present in normal proportion to one another, if one cell type is increased or decreased, or if immature or abnormal cells are present. This information is helpful in diagnosing specific types of illnesses that affect the blood.

White blood cells are made in your bone marrow or lymphoid system. They protect your body against infection and aid your immune system. If an infection develops, white blood cells attack and destroy the microorganism causing the infection.

How is the sample collected for testing?

The test is performed on a blood sample taken from a vein in the arm or from a finger-prick (for children and adults) or heel-prick (for infants).

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?

    The white blood cell differential assesses the ability of the body to respond to and fight infection. It can detect the severity of allergic and drug reactions, parasitic and other types of infection. It can also identify some types of leukaemia and lymphoma, and detect other diseases affecting the bone marrow.

  • When is it requested?

    The white blood cell differential is automatically run as part of the full blood count (FBC), which is requested for many different conditions.It is a common test that can indicate areas for further investigation.

  • What does the test result mean?

    The results indicate the relative percentage and actual numbers of each type of white blood cell that is present.

    Neutrophils can increase in response to bacterial infection, inflammatory disease, steroid medication, or more rarely leukaemia. Decreased neutrophil levels may be the result of severe infection, liver disease, enlarged spleens or other conditions, such as responses to various medications or chemotherapy.

    Eosinophils can increase in response to allergic disorders, inflammation of the skin, and parasitic infections. They can also occur in response to some infections or to various bone marrow malignancies.

    Basophils can increase in cases of leukaemia, long-standing inflammation, the presence of a hypersensitivity reaction to food, or radiation therapy.

    Lymphocytes can increase in cases of bacterial or especially viral infection, leukaemia, lymphoma and in people with underactive or absent spleens.  Decreased lymphocyte levels are common in later life but can also be due to steroid medication, stress, lupus, and HIV infection.

    Monocyte levels can increase in certain leukaemias, in response to infection of all kinds as well as to inflammatory disorders. Decreased monocyte levels can indicate bone marrow injury or failure and some forms of leukaemia - especially "hairy cell leukaemia".

  • Is there anything else I should know?

    Age, eating, physical activity, and stress may alter white blood cell differential values.  

    Long-term exposure to toxic chemicals (for example some solvents, petroleum products and insecticides) can increase the risk of an abnormal differential as can smoking.

  • What are the individual functions of each type of white blood cell?
    • Neutrophils, the most abundant white blood cells, are 'phagocytes' - that is, they 'eat' foreign organisms and kill them with internal poisons. They are important for fighting bacterial and fungal infections.
    • Lymphocytes are more specifically acting killers of infection and regulate the immune response. Some lymphocytes produce antibodies which 'remember' previous infections and guard against re-infection with the same organism. They are active against all types of infection including bacteria, fungi, parasites and viruses. When they malfunction they also have a role in allergy and in autoimmune diseases such as rheumatoid arthritis and lupus.
    • Monocytes are phagocytes, like neutrophils, active against bacteria and fungi.
    • Eosinophils increase during allergic reactions and some parasitic infestations such as worms.
    • Basophils control inflammation and damage to the body. They increase in some blood diseases and in some inflammatory bowel diseases
  • What are other names for neutrophils that might appear on a lab report?

    Neutrophils are also known as granulocytes, polymorphs, and PMNs.