Typical symptoms of diabetes mellitus are “three more and one less”, i.e., drinking more, eating more, urinating more, and losing weight. Diabetes mellitus symptoms have individual variability, and may be different in different patients. The symptoms of diabetes mellitus may vary from patient to patient. After the elevation of blood glucose, osmotic diuresis causes polyuria, followed by thirst and excessive drinking; peripheral tissues have impaired utilization of glucose, increased lipolysis, protein metabolism is negatively balanced, and symptoms of fatigue and emaciation gradually appear, and children’s growth and development are impeded; the patients are often prone to hunger and hyperphagia. Some diabetic patients may have skin itching, especially vulvar itching. When the blood sugar rises faster, it can make the osmotic pressure of the aqueous humor and lens change and cause refractive changes to blur vision. Many patients do not have any symptoms, and high blood sugar is only found during health checkups or laboratory tests for various diseases. When symptoms are detected, it is necessary to consult a doctor in a timely manner and receive standardized treatment under the guidance of a clinician.