High immunoglobulin M is commonly found in infectious diseases and autoimmune diseases, etc. It is recommended to consult the doctor in time and improve the examination to clarify the cause of the disease. Immunoglobulin M has the functions of bactericidal, activating complement, immunoregulation and agglutination, and also participates in the pathological process of autoimmune diseases and hypersensitivity reactions. When the body is infected, autoimmune diseases can cause immunoglobulin M elevation, serum immunoglobulin M normal reference range of 0.5 ~ 2.5g / L. Elevated immunoglobulin M is commonly found in: intrauterine fetal infections, chronic or subacute infections, infectious mononucleosis, mycoplasma pneumonia, liver disease, connective tissue disease, macroglobulinemia, and asymptomatic monoclonal IgM disease. Therefore, it is also necessary to rely on the patient’s symptoms, signs and other indicators to determine the cause of the disease. Therefore, if you find high immunoglobulin M, it is recommended to go to the hospital in time, complete the relevant examinations, identify the cause of the disease, and follow the doctor’s instructions to standardize the treatment.