How To Interpret A High White Blood Cell Count

White blood cells, also known as leukocytes, are routinely measured on a common blood test called a complete blood count or CBC. White blood cells are an integral component of the body's immune system and are designed to fight infections caused by bacteria, viruses, parasites and fungi. The number of white blood cells in the body typically fluctuates between 4000 and 10,900 per microliter of blood. What factors can cause an increase in white blood cells  also known as a leukocytosis? What causes a high white blood cell count?

Infections frequently cause a high white blood cell count. When bacteria or viruses invade your body your immune system rapidly mounts a multi-pronged response including the production of numerous white blood cells. These white blood cells surround and eliminate the offending agents.

Cancer of the bone marrow called leukemia can occasional cause a high white blood cell count. Our bone marrows produce all the various components of our blood; among those components are white blood cells. When leukemia occurs the bone marrow cannot stop producing large numbers of white blood cells even though they're not needed.

Certain prescription medications can cause a high white blood cell count. The most frequent culprits are corticosteroids and anti-epileptic medications. High white blood cell counts resolve with discontinuation of the medications.

Severe allergic reactions can cause a high white blood cell count. In these cases the specific types of white blood cells involved are called eosinophils and basophils. Once the allergic reaction has resolved the high white blood cell count also resolves.

Chronic severe stress can cause a high white blood cell count. Stressed individuals produce high quantities of the flight or fight hormone epinephrine. Epinephrine in turn increases the number of white blood cells circulating in the blood stream.

Certain autoimmune disorders that cause whole body inflammation such as lupus or rheumatoid arthritis can stimulate the immune system to produce high numbers of white blood cells.

Very frequently no medical reason is found to explain a high white blood cell count. Your doctor will likely order a variety of laboratory tests and conduct a thorough history and physical exam. If no cause is found and you're asymptomatic it's likely that your doctor will choose to closely monitor you and repeat a complete blood count in a few weeks.        

*  A high white blood cell count should always be evaluated by a medial doctor.
*  Occasional a doctor specializing in the blood and immune systems called a hematologist may be consulted.