White blood cells have an important role to play in maintain body’s immunity as they are constantly searching the blood for disease causing bacteria, viruses and fungi. Whenever a disease causing foreign bacteria or virus enters your blood stream, leukocytes or the white blood cells recognizes and destroys them before the invading foreign particle can multiply in the body and cause disease.

The blood test that is used to measure the number of white blood cells or WBCs present in the blood is known as the WBC count. What is normal white blood cell count? How to interpret white blood cell count that is too high or too low?

What Is Normal White Blood Cell Count?

The normal WBC count is in between 4,300 and 10,800 cells per cubic millimeter (cmm) or 4.3 -10.8 x 10⁹ cells per liter. A range between 11 and 17 x 10⁹ /L is usually considered mild to moderate leukocytosis and a range between 3.0 and 5.0 x 10⁹ /L is usually considered mild leucopenia.

Note: Normal WBC count ranges usually vary slightly among various laboratories where the test is conducted. You should always consult your physician to know about the significance of your specific test results. The examples of ranges mentioned above demonstrate the common measurements for results of WBC count. Some laboratories may use different units for measurements or may test different types of specimens.

How to Test White Blood Cell Count?

1. How Is the Test Done?

To do the test, blood is drawn from a vein usually located on the inside of the elbow or at the back of the hand. The site is cleaned with an antiseptic; an elastic band is wrapped around the upper arm so as to apply pressure to the area, thereby causing the vein to swell with blood. Next a needle is gently inserted into the vein and the blood is withdrawn into an airtight vial or tube that is attached to the needle. The needle is removed and a bandage applied to the puncture site. The blood sample is then sent to the laboratory for testing.

In young children or infants, a lancet, which is a sharp tool, is used to puncture the skin and draw the blood. The blood is collected onto a glass slide or a test strip or into a small glass tube known as a pipette. After the blood is collected a bandage is applied on the puncture wound to stop bleeding.

2. How to Prepare for the Test

Usually no preparation is needed to test for WBC. However, you should inform your physician about any medicines that you may be taking including over-the-counter ones. This is due to the fact that test results may be interfered by certain drugs.

Drugs that can increase the WBC count are: aspirin, allopurinol, corticosteroids, heparin, epinephrine, chloroform, quinine, and triamterene.

Drugs that can decrease the WBC count are: antibiotics, antihistamines, anticonvulsants, arsenicals, antithyroid drugs, barbiturates, diuretics, chemotherapy drugs and sulfonamides.

When the needle is inserted into the skin or vein to draw the blood you may feel mild to moderate pain. Some people may feel only the sensation of a prick or a stinging sensation. After the blood is withdrawn some people may feel slight amount of throbbing at the site.

3. What Are the Risks Involved?

Very little risk is involved in your blood being withdrawn for a WBC count. The size of the veins and the arteries vary in different individuals and collecting blood may be more difficult in some individuals than in others.

The various risks that may be associated with withdrawing blood, though slight are:

• Bleeding in excess
• Feeling faint or light-headed
• Accumulation of blood under your skin, also known as a hematoma
• nfection at the site where the skin is punctured

Why Is White Blood Cell Count Tested?

A WBC count is always performed as a part of a complete blood count or CBC. A complete blood count and hence your WBC count is usually ordered by physicians during an annual physical examination. A WBC count is also recommended in case you develop complaints of fever, chills, headaches or persistent body pains. A WBC count is used to detect infections hiding in your body and can alert physicians regarding the undiagnosed medical illnesses including autoimmune diseases, blood disorders and immune deficiencies. WBC count is also used by physicians to monitor the effectiveness of chemotherapy or radiation treatment in patients suffering from cancer.

What Do Abnormal Test Results Mean?

1. High WBC

An increased WBC count is also known medically as leukocytosis. It usually occurs in the following conditions:

• Anemia
• Infectious diseases
• Bone marrow tumors
• Inflammatory diseases such as allergies and rheumatoid arthritis
• Leukemia
• Tissue damage, for example that occurs in burns
• Severe stress, either emotional or physical
• Individuals who have their spleen removed will always show a slightly larger number of WBC’s.

2. Low WBC

A reduced or low WBC count is also known as leucopenia. It can occur in the following conditions:

• Diseases of the spleen or liver
• Collagen vascular diseases such as SLE (systemic lupus erythematosus)
• Bone marrow deficiency or bone marrow failure, for instance, it can occur as a result of infection, abnormal scarring or tumor
• Radiation therapy or exposure to radiation