Hematocrit, also called hematocrit, is the percentage of blood cell volume to total blood volume, which is normally 40%-50% for adult males and 37%-48% for adult females. Hematocrit is affected by several factors such as blood volume and red blood cell volume. For example, in cases of blood concentration, such as heavy sweating, severe nausea, vomiting, diarrhea, etc., a relative increase in hematocrit may occur due to a decrease in plasma volume. If the number of red blood cells is abnormally high, such as in chronic obstructive pulmonary disease and true erythropoietic disease, the hematocrit will be significantly increased, especially in true erythropoietic disease, where the hematocrit can even reach 60%-80% due to the abnormally high number of red blood cells. If the hematocrit is low, the most common cause is anemia caused by various diseases, such as iron deficiency anemia, megaloblastic anemia, aplastic anemia, etc., the hematocrit will appear significantly lower.