Low white blood cell count

A low white blood cell count is a lower number of the cells in the blood that fight illness.

What's thought of as low in a white blood cell count varies from one lab to another. This is because labs set their own reference ranges based on the people they serve. Most often, a count lower than 3,500 white blood cells per microliter of blood is thought to be low for adults. For children, an expected count depends on the age.

Some people can have white blood cell counts that are lower without being ill. For instance, Black people tend to have lower counts than white people do.

White blood cells come from the spongy tissue called bone marrow inside some of the larger bones. Conditions that affect the bone marrow are most often the causes of low white blood cell count. Some of these conditions are present at birth, also called congenital.

Causes of a low white blood cell count include:

• Aplastic anemia
• Chemotherapy
• Epstein-Barr virus infection
• Hepatitis A
• Hepatitis B
• HIV/AIDS
• Infections
• Leukemia
• Lupus
• Rheumatoid arthritis
• Malaria
• Medicines, such as antibiotics
• Poor nutrition and lack of certain vitamins
• Radiation therapy
• Sarcoidosis
• Sepsis
• Tuberculosis

A test a healthcare professional orders to diagnose a condition can show a low white blood cell count. A low white blood cell count rarely is found by chance.

Talk to your healthcare professional about what your results mean. A low white blood cell count plus results from other tests might show the cause of your illness. Or you might need other tests to find out more about your condition.

A very low white blood cell count over time means you can get infections easily. Ask your healthcare professional about ways to stay safe from illnesses that pass from one person to the next. Wash your hands regularly and well. Think about wearing a face mask. Stay away from anyone with a cold or other illness.