For adults, leukocyte 11.9×10^9/L is a mild increase. Whether leukocyte 11.9×10^9/L is serious or not depends on the cause of the mild increase in leukocytes. For example, when the human body after strenuous exercise, emotional or in a high temperature or cold environment, the number of white blood cells will appear mildly increased, may appear white blood cells 11.9 × 10^9 / L, this time belongs to a normal physiological changes, no obvious impact on the human body, the consequences are not serious. If an infection occurs in the body, such as acute appendicitis or acute gastroenteritis, a leukocyte 11.9×10^9/L may also occur. These inflammatory conditions can be cured after surgical treatment and antibacterial medication, and there are no obvious consequences. However, if the white blood cell 11.9×10^9/L is accompanied by anemia and thrombocytopenia, it cannot be excluded that it is caused by acute leukemia, and if it is diagnosed as acute leukemia, the consequences will be very serious. So whether or not the leukocyte 11.9×10^9/L is serious depends critically on the specific cause of the increased leukocytes.