What Does It Mean When You Have a Low White Blood Cell Count?

A low white blood cell count is an indicator of serious infections, bone marrow deficiency, autoimmune disorders and certain types of cancer, according to MedlinePlus. Several types of medications, such as anti-seizure drugs and chemotherapy drugs, also cause decreased WBC counts.

White blood cells help the immune system fight infections, explains MedlinePlus. A normal WBC count ranges from 4,500 to 10,000 cells per microliter. Mononucleosis, spleen disorders, liver diseases and lupus are some of the causes of a reduced WBC count. Antibiotics, diuretics and anti-thyroid drugs can also reduce the number of WBCs in the blood.

There are five major types of white blood cells, notes the University of Rochester Medical Center. Basophils let other white blood cells know when a foreign substance has entered the bloodstream and participate in the body's immune response by releasing histamine and other chemicals. Eosinophils participate in the allergic response, destroy parasites and kill cancer cells. Monocytes break down bacteria, preventing infections from getting out of control. Lymphocytes defend the body against infections by producing antibodies to certain organisms. Neutrophils are the first WBCs to respond when a foreign substance infects the body. They help the body fight infection by digesting fungi and bacteria.

Many diseases and disorders can cause a low white blood cell count. Some of these diseases are manageable, while others are more serious. AIDS, hepatitis, leukemia, lupus and aplastic anemia are some disorders that can cause this symptom. Certain medications, such as antihistamines, antibiotics and diuretics, can also make white blood cell production decrease. Because they are typically more susceptible to infection, some patients with a persistent low white blood cell count must take special precautions to prevent getting sick, explains Mayo Clinic. These precautions include washing hands regularly, avoiding people with colds or other illness, and wearing a face mask. Serious complications, such as infections or organ failure, can arise if the problem is not treated quickly.

Doctors order a white blood cell count, along with other tests, to help diagnose illnesses, according to Mayo Clinic. No preparation is usually necessary before a white blood cell count, which is obtained by taking a blood sample from a vein, states MedlinePlus. A normal white blood cell count ranges from 4,500 to 10,000 white blood cells per microliter. Because normal value ranges sometimes differ among laboratories, it's best for patients to discuss individual results with their doctor.