Erythrocytosis is defined as a higher than normal number of red blood cells per unit volume of peripheral blood, hemoglobin and hematocrit. In adult men, hemoglobin is 16.5 g/dL or hematocrit is 49%; in adult women, hemoglobin is 16.0 g/dL or hematocrit is 48%. The causes of erythrocytosis are categorized as absolute and relative. 1. Absolute erythrocytosis includes true and secondary erythrocytosis, which may be caused by neonatal erythrocytosis, plateau erythrocytosis, chronic lung disease, pulmonary hyperventilation syndrome, cardiovascular disease, and bone marrow proliferation. 2. Relative erythrocytosis is mainly caused by water loss or shock, and there is also a condition called pseudoerythrocytosis. It may be related to mental stress, long-term smoking, hypertension or excessive obesity. If the patient has the above symptoms, he should go to the regular hospital in time, under the guidance of professional doctors to avoid delaying the condition.