Leukocytosis is an increase in the content of leukocytes in the peripheral blood above 9000 in 1 μl (9x109 / l). It is observed in a wide range of nosologies, especially bacterial and viral infections, systemic inflammatory pathologies of a rheumatic nature. There are no specific clinical manifestations. Symptoms are determined by the cause, i.e. disease, against the background of which leukocytosis developed. The level of leukocytes is measured when taking venous or capillary blood in the morning 12 hours after the last meal. The white blood cell count is part of a complete blood count. To correct leukocytosis, the underlying disease is treated.