Whole blood viscosity is a comprehensive index of plasma viscosity, hematocrit, red blood cell deformability and radical aggregation capacity, platelets, and leukocyte rheological properties. The higher the viscosity, the lower the mobility and the longer the time required to pass through the capillaries. The lower the viscosity, the higher the mobility. Increased viscosity of whole blood is commonly seen in abnormal plasma proteins, increased number of red blood cells, abnormal red blood cell mass and other types of diseases, such as myocardial infarction. Decreased viscosity of whole blood is common in bleeding disorders.