The symptoms of diabetes mellitus can be divided into two categories: one is the manifestation related to metabolic disorders, especially the “three polyand one less” related to hyperglycemia, which is mostly seen in type 1 diabetes mellitus, and type 2 diabetes mellitus is often not very obvious or only partially manifested; the other category is the manifestation of various acute and chronic complications. Polydipsia is caused by high blood sugar, exceeding the renal glucose threshold (8.89-10.0mmol/L), and the glucose filtered out by the glomerulus cannot be completely reabsorbed by the renal tubules, forming osmotic diuresis. The higher the blood glucose, the more urinary sugar excretion, the more urine volume, 24h urine volume can be 5000 ~ 10000ml, but the elderly and people with kidney disease, the renal glucose threshold increases, urinary sugar excretion is impaired, in a mild to moderate increase in blood glucose, polyuria may not be obvious. 2.Drinking Mainly due to high blood glucose, plasma osmolality increases significantly, combined with polyuria, excessive water loss, intracellular dehydration, aggravating hyperglycemia, further increasing plasma osmolality, stimulating the thirst center, resulting in thirst and drinking. Polydrinking further aggravates polyuria. 3, polyphagia The mechanism of polyphagia is not very clear. Most scholars tend to think that it is caused by the decrease of glucose utilization (the difference of glucose concentration in arterial and venous blood before and after entering and leaving the tissue cells). Normal people fasting when the arterial and venous blood glucose concentration difference is reduced, stimulating the feeding center, resulting in hunger; after ingestion of food, blood glucose, arterial and venous blood concentration difference increased (greater than 0.829mmoL / L), the feeding center is inhibited, the satiety center is excited, feeding requirements disappear. However, in diabetic patients, due to absolute or relative lack of insulin or insensitivity of tissues to insulin, the ability of tissues to take in and use glucose is reduced, although blood glucose is at a high level, the difference in concentration of glucose in arterial and venous blood is very small, and tissue cells are actually in a “starvation state”, thus stimulating the feeding center and causing hunger and overeating; in addition, the In addition, the body can not make full use of glucose, a large amount of glucose excretion from the urine, so the body is actually in a state of semi-starvation, lack of energy also caused by hyperphagia. 4. Weight loss Diabetic patients lose weight despite normal appetite and food intake, or even increase, mainly because of absolute or relative lack of insulin or insulin resistance, the body cannot make full use of glucose to produce energy, resulting in enhanced fat and protein decomposition, excessive consumption, negative nitrogen balance, weight loss gradually, and even wasting. Once diabetes is reasonably treated and well controlled, weight loss can be controlled and even regained. If a diabetic patient continues to lose weight or lose weight significantly during the treatment process, it suggests that the metabolism may be poorly controlled or combined with other chronic wasting diseases. 5.Lack of energy is also common in diabetic patients, because glucose can not be fully oxidized, that is, the body can not fully utilize glucose and effectively release energy, while tissue water loss, electrolyte imbalance and negative nitrogen balance, etc., and therefore feel general weakness, depression. 6, vision loss Many diabetic patients complain of vision loss or blurred vision when they visit the clinic in the early stage, which may be mainly due to the change of crystal osmolarity caused by hyperglycemia, resulting in the change of crystal refraction. In the early stage, most of the changes are functional, and once the blood sugar is well controlled, the vision can return to normal sooner. Diabetic ketoacidosis, hyperosmolar non-ketotic diabetic coma, diabetic lactic acidosis, diabetic skin infection, diabetic foot, diabetic gastroparesis, diabetic cardiomyopathy, diabetic heart disease, diabetes and hypertension, diabetic nephropathy, diabetic complication of urinary tract infection, diabetic neuropathy, diabetic peripheral neuropathy, diabetes-induced Myelopathy, diabetic retinopathy, diabetic uveitis, diabetes with tuberculosis, etc.