Overview
White blood cells (WBCs), also called leukocytes, are an important part of the immune system. These cells help fight infections by attacking bacteria, viruses, and germs that invade the body. White blood cells originate in the bone marrow, but circulate throughout the bloodstream. There are five major types of white blood cells:
- neutrophils
- lymphocytes
- eosinophils
- monocytes
- basophils
Purpose of a WBC Count
It is normal for doctors to order a complete blood count
and check your WBC count during an annual physical examination. Your doctor may
recommend a WBC count if you complain of persistent body aches, fever, chills, or headaches.
A WBC count can detect hidden infections within your body and alert doctors to
undiagnosed medical conditions, such as autoimmune
diseases, immune deficiencies, and blood disorders. This test also
helps doctors monitor the effectiveness of chemotherapy or radiation treatment
in cancer patients.
What to Expect from
a WBC Count
A healthcare provider or lab technician will draw blood
to check your WBC count. This blood sample is taken either from a vein in your
arm or a vein on the back of your hand. It only takes a couple of minutes to draw
your blood and you may experience minor discomfort. The healthcare provider
will clean the needle site to kill any germs and then tie an elastic band
around the upper section of your arm. This elastic band is used so that the
blood can fill the vein making it easier for the blood to be drawn.
The healthcare provider slowly inserts a needle into your
arm or hand, and collects the blood in an attached tube. The provider then
removes the elastic band from around your arm and slowly removes the needle.
The technician applies gauze to the needle site to stop the bleeding.
Healthcare providers use a different technique when
drawing blood from young children and infants. With these patients, providers
first puncture the skin with a lancet (a pricking needle) and then use a test
strip or a small vial to collect the blood. Results are sent to a lab for
review.
How to Prepare for a
WBC Count
A WBC count requires no specific preparation. You simply
schedule an appointment with your doctor or set up an appointment at a local
medical laboratory. Certain medications can interfere with your lab results and
either lower or increase your WBC count.
A list of just a few drugs that may affect your test
results includes:
- corticosteroids
- aspirin
- heparin
- triamterene
- antibiotics
- antihistamines
- diuretics
- barbiturates
- sulfonamides
- chemotherapy medication
Prior to having your blood drawn, tell your doctor about
all prescription and nonprescription medications that you’re currently taking.
Understanding WBC
Count Test Results
An average normal range for white blood cells is between
4,500 and 10,000 mcl. Abnormal test results are classified by numbers that are
higher or lower than this range. It’s important to note that age can also
affect the number of white blood cells, with infants having a higher count than
adults.
A low or high WBC count can point to a blood disorder or
other medical conditions. To identify the exact cause of a high or low WBC
count, your doctor will take several factors into consideration, such as your
list of current medications, medical symptoms, and medical history.
Leukopenia is the medical term used to describe a low WBC
count. Conditions or illnesses that can trigger a low number include:
- HIV
- autoimmune disorders
- bone marrow disorders/damage
- lymphoma
- severe infections
- liver and spleen diseases
- lupus
- radiation therapy
Leukocytosis is the medical term used to describe a high
WBC count. Conditions or illnesses that can trigger a high number include:
- anemia
- tumors in the bone marrow
- leukemia
- inflammatory conditions, such as arthritis and bowel disease
- stress
- exercise
- tissue damage
- pregnancy
- allergies
- asthma
After diagnosing the cause of a high or low WBC count and
recommending a treatment plan, doctors will periodically re-check your white
blood cells. If your white blood cell count remains high or low, this can
indicate that your condition has worsened and your doctor may adjust your
treatment. If your WBC count shows a normal range, this indicates that the
treatment is working.
Having your blood drawn is a simple procedure and
complications are extremely rare. It can be difficult to take blood from people
with small veins. The lab technician may be unable to locate a vein, or once
the needle is inside the arm or hand, the lab technician may have to move the
needle around in order to draw blood. This can cause a sharp pain or a stinging
sensation. Rare complications that can occur include:
- infection at the needle site
- excessive bleeding
- lightheadedness or fainting
- bleeding underneath the skin (hematoma)
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