Normal adult male red blood cell count (4.0~5.5) x 10^12/L, normal adult female red blood cell count (3.4~5.0) x 10^12/L. Multiple examinations of adult male red blood cell >6.0 x 10^12/L and adult female red blood cell >5.5 x 10^12/L are considered high. There are many dangers of high red blood cells, such as blood clots, high blood pressure and hypersplenism. 1. Thrombus: Due to the increase of red blood cells, the blood is viscous and the blood flow rate decreases, leading to the deposition of platelets and fibrin, which leads to the formation of thrombus. Blood clots can lead to myocardial infarction, cerebral infarction and other diseases. 2. Hypertension: the increase in red blood cells leads to an increase in blood volume and an increase in cardiac load, and hypertension occurs in the vast majority of patients. 3. Hypersplenism: Aged red blood cells can be cleared through the spleen. When red blood cells increase, the metabolic load of the spleen increases, resulting in hypersplenism, splenomegaly, and splenic discomfort. A transient increase in red blood cells can be adjusted to a normal level by its own metabolism and does not require excessive concern. However, when the red blood cells are persistently high, we should be vigilant and go to the hospital for further examination in time to avoid delaying the condition.