Red blood cell volume, also known as hematocrit, its normal range is adult male 0.4 ~ 0.5, adult female 0.37 ~ 0.48, 51.2% is slightly higher, the situation is serious, according to the causes of hematocrit to determine, physiological increase is not serious, pathological increase need to pay attention to the more serious, specific as follows: 1. Physiological factors (1) Sweating and drinking too little water: sweating and drinking too little water will lead to blood concentration, which will lead to the situation of high hematocrit, and this situation will be relieved by drinking water appropriately, which is not serious. (2) in the plateau: if you live in the plateau for a long time in the oxygen-poor environment, the body in order to adapt to the environment, the number of red blood cells will increase, so the hematocrit of 51.2% is normal. 2. Pathological factors (1) True erythrocytosis: the main manifestation of true erythrocytosis is an increase in the number of red blood cells, which is very serious, and some patients may even develop acute leukemia. (2) Coronary heart disease: if you suffer from coronary heart disease, the oxygen-carrying capacity of red blood cells will be reduced, and the patient’s body will have long-term hypoxia, which will stimulate the increase in the number of red blood cells, which is a more serious situation. (3) Blood tumor: Suffering from blood tumor is likely to cause massive proliferation of red blood cells, resulting in hematocrit 51.2%, which is a very serious situation. In the case of hematocrit 51.2%, it is recommended to go to the hospital to find out the cause of the disease, so as to facilitate the formulation of countermeasures.