White blood cells are specialized cells that help protect the body from infections and other threats. They are produced mainly in the bone marrow and travel through the bloodstream and tissues as part of the immune system.
There are several types of white blood cells, and each has a different function. Neutrophils help respond to many infections, lymphocytes support targeted immune responses, and monocytes assist with removing harmful organisms and damaged cells. Eosinophils and basophils also contribute to immune and inflammatory processes.
The number and type of white blood cells can provide valuable information about a person's health. Doctors commonly evaluate them through a CBC blood test, which measures different blood components.
WBC levels can change because of infections, inflammation, medications, immune system conditions, or disorders affecting the blood and bone marrow. Both unusually high and unusually low counts may require further evaluation when they persist or occur alongside other symptoms.
If you have an unexplained change in your white blood cell count, your healthcare provider can help determine what it means in the context of your overall health. A hematologist may recommend additional tests if a blood or bone marrow disorder is suspected.