The standard of blood glucose is not related to age, the normal fasting blood glucose range should be between 3.9mmol/L~6.1mmol/L. The diagnosis of diabetes mellitus should also be combined with clinical symptoms, fasting blood glucose or OGTT test, etc. It is recommended to consult your doctor. Diabetes has many causes, including genetic factors, autoimmune and environmental factors. The diagnosis of diabetes mellitus can be confirmed by the presence or absence of the three symptoms of diabetes mellitus, in addition to the blood glucose level, and other laboratory tests, such as glycosylated hemoglobin, etc. Diabetes mellitus can affect many parts of the body. Diabetes can involve many organs throughout the body, and complications are numerous and complex, such as susceptibility to infections, diabetic foot, etc. Older people should monitor their blood glucose levels regularly, and seek medical attention if they find abnormalities in their blood glucose levels.