The white blood cell count measures how many leukocytes circulate in a volume of blood. These cells are the mobile part of the immune system, dealing with infection, clearing damaged tissue and driving inflammatory and allergic responses. The count is a broad indicator of immune activity and of how well the bone marrow is producing these cells.
No readings for this marker yet.
A raised count most often reflects an ongoing bacterial infection or another inflammatory process, and also rises with physical stress, tissue injury and corticosteroid treatment. A lowered count is seen with some viral infections, with certain autoimmune conditions, and where the marrow is suppressed, including as a reaction to particular medicines. Both directions describe activity, not a named illness, and a value outside the usual range is a reason for a repeat test and a doctor's assessment.
The count fluctuates through the day and rises transiently after heavy exercise, a large meal, smoking or acute emotional stress, so timing of the draw matters; pregnancy raises it throughout gestation, shifting the applicable range. Several drugs are monitored specifically through this test, among them metamizole, thiamazole, co-trimoxazole, metronidazole, terbinafine and mirtazapine. It is read together with the differential count, particularly the absolute neutrophil and lymphocyte figures, since the total says little about which population has changed.
Reference ranges are general adult values and depend on lab, assay, age and sex. For orientation, not diagnosis — discuss results with your doctor.