Blood viscosity is related to two factors: first, it is related to the number of blood cells in the blood, the deformability of red blood cells and the adhesion aggregation of platelets. Second, it is related to the changes in the concentration of various solutes dissolved in the plasma. There are two most common cases of low blood viscosity: first, the number of blood cells in the blood decreases, such as anemia, and when the number of red blood cells decreases, the blood viscosity decreases, and the common ones are megaloblastic anemia, aplastic anemia, iron deficiency anemia, hemolytic anemia, and so on. Therefore, if the blood viscosity is low, you need to go to the hematology department for routine blood tests to see if you are anemic. If it is anemia, find the cause of anemia, give symptomatic treatment, and the low blood viscosity will improve. Second, the concentration of fibrinogen in the plasma is reduced to cause the blood viscosity to decrease, you can go to the hospital to test the concentration of fibrin, if the concentration of fibrin is significantly reduced, it can cause the blood viscosity to decrease, you need to supplement fibrinogen treatment.