When we are not feeling well and go to the hospital for a checkup, the doctor usually writes out a stack of test slips for us to check. One of them is blood sedimentation, and many people are not sure what this blood sedimentation is? Why do we need to check the blood sedimentation? Is it something that doctors prescribe indiscriminately in order to charge us more? In order to clear up this confusion, we still need to understand what the blood sedimentation is. Hematocrit is the common name for the sedimentation rate of red blood cells. When anticoagulated blood is placed vertically in a sedimentation tube, the red blood cells sink due to their higher density. The sedimentation rate of red blood cells is usually expressed in terms of the distance they have sunk by the end of the first hour and is called the erythrocyte sedimentation rate. The rate of sedimentation is related to plasma viscosity, especially to the aggregation force between red blood cells. If the aggregation force between red blood cells is large, the sedimentation rate will be fast, and vice versa. Because of this, blood sedimentation is commonly used in hospitals as an indicator of red blood cell aggregation, which can reflect certain diseases within the body. So through the blood sedimentation test, can reflect the body of internal lesions? First, accelerated blood sedimentation is not necessarily a disease, but may also be some physiological phenomena, such as women’s menstrual period, pregnancy, the elderly, especially the elderly over 60 years old, mostly due to the increase of fibrinogen and lead to increased blood sedimentation. Second, the blood sedimentation accelerated reaction in the pathology, mostly with a variety of inflammation (acute and chronic inflammation, such as tuberculosis, connective tissue disease, rheumatic fever, etc.). There is also tissue injury and necrosis, which can also increase in the short term. It is more obvious in malignant tumors, especially those with high malignancy and rapid growth. Third, in many kinds of hyperglobulinemia, increased blood sedimentation can also be seen, such as systemic lupus erythematosus, multiple myelopathy, macroglobulinemia, cirrhosis of the liver, chronic nephritis and so on. Fourth, in anemia, hypercholesterolemia can also appear sedimentation rate. As a result, the etiology of accelerated blood sedimentation is complex and nonspecific. Fifth, the vast majority of accelerated blood sedimentation is acute or chronic infection, malignant tumors and diseases with tissue degeneration or necrosis (such as myocardial infarction, collagenous tissue disease, etc.) have changes in plasma globulin and fibrinogen, or abnormal proteins enter the blood, resulting in accelerated blood sedimentation. Sixth, anemia and menstruation and after the third trimester of pregnancy can also accelerate blood sedimentation. Therefore, blood sedimentation is a non-specific test and cannot be used alone to diagnose any disease. VII.Slowed blood sedimentation can be seen in true erythrocytosis. So many problems can be detected through the blood sedimentation test. Then we should understand why doctors must let us do the blood sedimentation test.