A low white blood cell count in adults is less than 4,000 cells per microliter of blood. A low white blood cell count can be an indicator of certain conditions, including lupus, rheumatoid arthritis, vitamin deficiencies, or a side effect of cancer treatment. Possible Causes.

Is low white blood count serious?

A low WBC count can be serious because it increases your risk of developing a potentially life-threatening infection. Seek prompt medical care if you have a low WBC count and have signs of an infection, such as a fever, swollen lymph nodes, sore throat, or skin lesions.

What happens if WBC count is low?

White blood cells are produced by your bone marrow to help your body fight infection. If you have fewer than normal white blood cells, you have a higher risk of getting an infection. When you have a low white blood cell count, your immune system isn't working as well as it should.