The clinical manifestations of diabetes mellitus are often described as “three more and one less”, i.e., polyuria, polydipsia, polyphagia, and weight loss. There is individual variability in the clinical manifestations of diabetes mellitus. Some patients may be asymptomatic. Diabetes mellitus patients with elevated blood glucose due to osmotic diuresis caused by polyuria, followed by thirst and drinking; peripheral tissues of glucose utilization disorder, increased lipolysis, protein metabolism negative balance, gradually appeared fatigue, emaciation, children’s growth and development is impeded; the patient is often prone to hunger, polyphagia. Some diabetic patients may have skin itching, especially vulvar itching. When the blood sugar rises faster, the osmotic pressure of the aqueous humor and lens can be changed, causing refractive changes and blurred vision. It is recommended to consult a doctor when the above symptoms of diabetes occur.