The typical symptoms of diabetes mellitus are three more and one less, i.e. polyuria, polydipsia, polyphagia and weight loss, but most patients in the clinic have no obvious symptoms. Diabetes mellitus is a group of metabolic diseases characterized by elevated blood glucose caused by multiple etiologies, and is caused by absolute or relative insulin deficiency. Commonly, there are type 1 diabetes mellitus and type 2 diabetes mellitus, which have different symptoms and manifestations. Patients with type 1 diabetes have the typical symptoms of three more and one less, and are prone to diabetic ketoacidosis, which manifests itself in weakness, nausea, vomiting, dry skin and mucous membranes, drop in blood pressure, and impaired consciousness, etc. Type 2 diabetes often occurs in obese people or people with a family history of diabetes, which has a more insidious onset, and the symptoms are relatively mild, and poor glycemic control can be associated with ketoacidosis, hyperosmolar coma, etc. People who suspect diabetes can go to the hospital to have a checkup, and then they will be treated for the disease. People who suspect diabetes can go to the hospital to get a clear diagnosis.