How much does a white blood cell count fluctuate in a day?
Normally, not much
Unless you are exposed to agents that lower white count (high dose radiation, chemotherapeutic agents, some poisons) or become infected rapidly (which increases white count) generally the white blood cell count is a value that does not fluctuate that much over the course of a 24 hour period.
As an example, if you acquire a very rapidly progressing community-acquired pneumonia, WBC does go up fast.
WHITE BLOOD CELL