The age of onset of diabetes varies according to the type of disease, for example, the age of onset of type 2 diabetes is usually after 40 years of age. 1. Type 1 diabetes mellitus: the age of onset is usually less than 30 years old; the symptoms of “three more and one less” (i.e., polyuria, polydipsia, polyphagia, and weight loss) are obvious; ketoacidosis or ketoacidosis are often the starting point of the disease; the non-obese body type; the serum C-peptide concentration in the fasting or postprandial period is significantly reduced; and the appearance of pancreatic islet autoimmune markers. 2. Type 2 diabetes: a heterogeneous group of diseases. It can occur at any age, but is more common in adults, often starting after 40 years of age; most of them have insidious onset, relatively mild symptoms, more than half of them do not have any symptoms; a lot of patients due to chronic complications, concomitant diseases, or only found in the health examination. There is often a family history. Diabetes must be found in a timely manner to seek medical attention and receive regular treatment.