Leukocytosis is the condition characterised by an elevated white blood cell (WBC) count, typically exceeding 11,000 cells per microlitre of blood. This increase often indicates an underlying response to infection, inflammation, or stress, making it crucial for diagnosing various medical conditions. A common association is with bacterial infections, where leukocytosis serves as a key indicator for the body's immune response and can guide further diagnostic and therapeutic decisions.