High plasma viscosity is an indicator of plasma fluidity. High plasma viscosity indicates poor plasma fluidity and is commonly associated with a significant increase in the content of various solute components in the plasma, the most common causes being: First, high blood glucose. Second, the common cause is high blood lipid, including high plasma triglyceride, total cholesterol and lipoprotein concentration, will cause high plasma viscosity. When blood lipids are reduced, plasma viscosity also decreases significantly. Third, in patients with multiple myeloma, monoclonal immunoglobulins are produced, and these immunoglobulins can increase plasma viscosity significantly. When the disease of multiple myeloma is controlled, the plasma viscosity also decreases.