Blood Differential
Reviewed
Also called: Complete blood count (CBC) with differential, Differential, White blood cell differential count, Leukocyte differential count, Peripheral Differential
A blood differential test measures the amount of each type of white blood cell (WBC) that you have in your blood.
Specimen: Blood
Why this test may be ordered
- As part of a routine checkup
- To help diagnose infections, autoimmune diseases, leukemia, or other cancers
- To monitor an existing blood disorder or related condition
- To investigate symptoms such as unusual tiredness, weakness, or unexplained bruising
Preparation and collection
No special preparation is necessary.
A health care professional will take a blood sample from a vein in your arm, using a small needle. After the needle is inserted, a small amount of blood will be collected into a test tube or vial. You may feel a little sting when the needle goes in or out. This usually takes less than five minutes.
There is very little risk to having a blood test. After the test, some people experience mild pain, dizziness, or bruising. These symptoms usually go away quickly.
Understanding results
Your blood differential test results may be higher or lower than normal for many reasons.
- High white blood cell count (leukocytosis): Conditions that may cause a high white blood cell count, also called leukocytosis, can include: Infections, Autoimmune or inflammatory disorders, Leukemia or Hodgkin disease, Allergic reactions, Certain steroids. Limitation: But abnormal results don't always mean you have a condition that needs medical treatment. Some other factors that may affect your results can include: Physical injury or extreme stress, Smoking, Alcohol use. Next step: If your results seem abnormal, your provider may order other tests to help figure out the cause.
- Low white blood cell count (leukopenia): Conditions that may cause a low white blood cell count, also called leukopenia, can include: Bone marrow diseases, Chemotherapy, Certain medicines, such as antibiotics, Cancer, HIV. Limitation: But abnormal results don't always mean you have a condition that needs medical treatment. Next step: To understand your results, your provider will also consider your symptoms, medical history, and the results of other blood tests.
- Abnormal results do not always mean you have a condition that needs medical treatment.
- Your provider will consider your symptoms, medical history, and other blood tests when interpreting results.
What to do next
If your results seem abnormal, your provider may order other tests to help figure out the cause. If you have questions about your results, talk with your provider.
- How do my results compare to the reference range used by my lab?
- What do my specific white blood cell levels mean for my health?
- Do I need any follow-up testing?
Evidence source
Source: U.S. National Library of Medicine (MedlinePlus). Practices and reference ranges may differ in your country.