Plasma viscosity is an indicator of plasma fluidity. High plasma viscosity, poor plasma mobility. Low plasma viscosity, the mobility of plasma is high. The most common original of low plasma viscosity is a significant decrease in the density of various solute components in plasma, such as congenital fibrinogen deficiency, and a significant decrease in fibrinogen concentration caused by severe liver diseases, such as cirrhosis and hepatocellular carcinoma, as well as a decrease in fibrinogen concentration caused by diffuse intravascular coagulation, which appears as low plasma viscosity. Secondly, a decrease in plasma immunoglobulin concentration, such as congenital immunoglobulin deficiency, and a decrease in immunoglobulin concentration due to other causes, can also cause a significant decrease in blood viscosity. The most common causes of high plasma viscosity are hyperglycemia, hyperlipidemia, and diseases such as multiple myeloma.