Blood sedimentation is the erythrocyte sedimentation rate, which refers to the rate at which red blood cells fall within one hour. If the blood sedimentation is normal, the following diseases can be ruled out: First, the active phase of various rheumatic diseases, such as rheumatoid arthritis, systemic lupus erythematosus, dry syndrome, etc. The blood sedimentation of these diseases will increase significantly during the active phase. Second, normal blood sedimentation can also exclude the active phase of rheumatic fever and tuberculosis, because when rheumatic fever is combined with medical history, the blood sedimentation will be significantly faster. Third, normal blood sedimentation can also exclude multiple myeloma. Patients with multiple myeloma will have abnormally fast blood sedimentation due to the production of monoclonal immunoglobulins, and if the blood sedimentation is normal, multiple myeloma can be excluded.