Blood viscosity is the viscosity of blood and is a test indicator of blood rheology. Blood viscosity is influenced by the number of various blood cells in the blood, their deformability, and the concentration of substances such as blood glucose, blood lipids and immunoglobulins in the plasma. Its normal range is 3.84-5.30 mPa-s in men and 3.39-4.41 mPa-s in women. increased blood viscosity is commonly seen in coronary heart disease, myocardial infarction, hypertension, cerebral thrombosis, diabetes, hyperlipidemia, malignancy, pulmonary heart disease, true erythrocytosis, multiple myeloma, primary macroglobulinemia, burns, etc. Decreased blood viscosity, mainly seen in anemia, severe fibrinogen and other coagulation factor deficiencies.