Self-measurement of diabetes may not be accurate, the diagnosis of diabetes mellitus needs to be made by a professional doctor based on the results of the examination and clinical symptoms, etc. Self-measurement of blood glucose results can be used as a reference, but can not be used as the basis for a definitive diagnosis of diabetes mellitus. The diagnosis of diabetes mellitus is based on the typical symptoms of “three more and one less” (drinking more, urinating more, eating more, and losing weight), plus the measurement of venous plasma glucose ≥11.1mmol/L, fasting blood glucose ≥7.0mmol/L, or 2-hour blood glucose ≥11.1mmol/L after glucose tolerance test, which can be diagnosed as diabetes mellitus if one of them meets the diagnosis of diabetes mellitus. One of them is enough for a diagnosis of diabetes mellitus. The China Type 2 Diabetes 2020 Prevention and Control Guidelines include glycated hemoglobin in the diagnostic criteria, and glycated hemoglobin ≥6.5% can be used as an additional diagnostic criterion for diabetes, but diabetes cannot be ruled out at less than 6.5%. If you find high or low blood glucose after self-testing, it is recommended to go to the hospital in time for further examination and definitive diagnosis and treatment under the guidance of a professional doctor, so as not to delay the condition.