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Basophil (close-up)
Basophil (close-up)

Formed elements of blood
Formed elements of blood

Blood differential test


The blood differential test measures the percentage of each type of white blood cell (WBC) that you have in your blood. It also reveals if there are any abnormal or immature cells.

Alternative Names:

Differential; White blood cell differential count

How the Test is Performed:

A blood sample is needed.

A laboratory specialist takes a drop of blood from your sample and smears it onto a glass slide. The smear is stained with a special dye, which helps tell the difference between various types of white blood cells.

Five types of white blood cells, also called leukocytes, normally appear in the blood:

  • Neutrophils
  • Lymphocytes (B cells and T cells)
  • Monocytes
  • Eosinophils
  • Basophils

A specially designed machine or a health care provider counts the number of each type of cell. The test shows if the number of cells are in proper proportion with one another, and if there is more or less of one cell type.

How to Prepare for the Test:

No special preparation is necessary.

How the Test will Feel:

When the needle is inserted to draw blood, some people feel moderate pain. Others feel only a prick or stinging. Afterward, there may be some throbbing or slight bruising. This soon goes away.

Why the Test is Performed:

This test is done to diagnose an infection, anemia , or leukemia. It may also be used to monitor one of these conditions, or to see if treatment is working.

Normal Results:

The different types of white blood cells are given as a percentage:

  • Neutrophils: 40 to 60%
  • Lymphocytes: 20 to 40%
  • Monocytes: 2 to 8%
  • Eosinophils: 1 to 4%
  • Basophils: 0.5 to 1%
  • Band (young neutrophil): 0 to 3%

What Abnormal Results Mean:

Any infection or acute stress increases your number of white blood cells. High white blood cell counts may be due to inflammation, an immune response, or blood diseases such as leukemia.

It is important to realize that an abnormal increase in one type of white blood cell can cause a decrease in the percentage of other types of white blood cells.

An increased percentage of neutrophils may be due to:

A decreased percentage of neutrophils may be due to:

An increased percentage of lymphocytes may be due to:

A decreased percentage of lymphocytes may be due to:

  • Chemotherapy
  • HIV infection
  • Leukemia
  • Radiation therapy or exposure
  • Sepsis
  • Steroid use

An increased percentage of monocytes may be due to:

  • Chronic inflammatory disease
  • Leukemia
  • Parasitic infection
  • Tuberculosis
  • Viral infection (for example, infectious mononucleosis, mumps, measles)

An increased percentage of eosinophils may be due to:

An increased percentage of basophils may be due to:

A decreased percentage of basophils may be due to:

  • Acute infection
  • Cancer
  • Severe injury


There is very little risk involved with having your blood taken. Veins and arteries vary in size from one patient to another, and from one side of the body to the other. Taking blood from some people may be more difficult than from others.

Other risks associated with having blood drawn are slight, but may include:

  • Excessive bleeding
  • Fainting or feeling lightheaded
  • Hematoma (blood accumulating under the skin)
  • Infection (a slight risk any time the skin is broken)


Vajpayee N, Graham SS, Bem S. Basic examination of blood and bone marrow. In: McPherson RA, Pincus MR, eds. Henry's Clinical Diagnosis and Management by Laboratory Methods. 22nd ed. Philadelphia, PA: Elsevier Saunders; 2011:chap 30.

Review Date: 1/27/2015
Reviewed By: Yi-Bin Chen, MD, Leukemia/Bone Marrow Transplant Program, Massachusetts General Hospital, Boston, MA. Also reviewed by David Zieve, MD, MHA, Isla Ogilvie, PhD, and the A.D.A.M. Editorial team.

The information provided herein should not be used during any medical emergency or for the diagnosis or treatment of any medical condition. A licensed medical professional should be consulted for diagnosis and treatment of any and all medical conditions. Call 911 for all medical emergencies. Links to other sites are provided for information only -- they do not constitute endorsements of those other sites. © 1997- A.D.A.M., Inc. Any duplication or distribution of the information contained herein is strictly prohibited.

Contact Us: 1-800-245-3314 or (501) 329-3831 2302 College Avenue, Conway, Arkansas 72034
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