Understanding the WBC (white blood cell) count A white blood cell (WBC) count is a test that measures the number of white blood cells in your body. This test is often included with a complete blood count (CBC). The term “white blood cell count” is also used more generally to refer to the number of white blood cells in your body. There are several types of white blood cells, and your blood usually contains a percentage of each type. Sometimes, however, your white blood cell count can fall or rise out of the healthy range.

Types of WBCs 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

A normal WBC count Infants are often born with much higher numbers of WBCs, which gradually even out as they age. According to the University of Rochester Medical Center (UMRC), these are the normal ranges of WBCs per microliter of blood (mcL): Age range WBC count (per mcL of blood) newborns 9,000 to 30,000 children under 2 6,200 to 17,000 children over 2 and adults 5,000 to 10,000 These normal ranges can vary by lab. Another common measurement for the volume of blood is cubic millimeter, or mm3. A microliter and cubic millimeter equal the same amount. The types of cells that make up WBCs usually fall within a normal percentage of your overall WBC count. The normal percentages of the types of WBCs in your overall count are usually in these ranges, according to the Leukemia & Lymphoma Society (LLS): Type of WBC Normal percentage of overall WBC count neutrophil 55 to 73 percent lymphocyte 20 to 40 percent eosinophil 1 to 4 percent monocyte 2 to 8 percent basophil 0.5 to 1 percent Higher or lower numbers of WBCs than normal can be a sign of an underlying condition. Having a higher or lower percentage of a certain type of WBC can also be a sign of an underlying condition.

Symptoms of an abnormal WBC count The symptoms of a low WBC count include: body aches

fever

chills

headaches High WBC counts don’t often cause symptoms, although the underlying conditions causing the high count may cause their own symptoms. The symptoms of a low WBC count may prompt your doctor to recommend a WBC count. It’s also normal for doctors to order a CBC and check your WBC count during an annual physical examination.

What to expect from a WBC count A healthcare provider or lab technician needs to 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 first cleans the needle site to kill any germs and then ties an elastic band around the upper section of your arm. This elastic band helps the blood fill your 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. Finally, 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: 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.

Complications from a WBC count 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, they may have to move the needle around in order to draw blood. This can cause a sharp pain or a stinging sensation. Rare complications include: infection at the needle site

excessive bleeding

lightheadedness or fainting

bleeding underneath the skin (hematoma)