Neutrophils

The share of your white cells that hunt bacteria. They are the largest fraction and the shortest-lived.

They are the part of the count that rises fastest in a bacterial infection, and the part that some medications and chemotherapy suppress first.

This is a percentage, so it can move purely because another fraction moved. The absolute count, if your lab prints one, is the number that matters. A modest rise follows hard exercise, stress or a steroid dose within hours.

Worth discussing a persistently low value, which matters more than a high one.