Postprandial blood glucose reaches 30.0 mmol per liter, a condition that indicates very high blood glucose. Diabetes mellitus can be diagnosed if accompanied by diabetic symptoms (excessive drinking, urination, overeating, unexplained weight loss). If not controlled in time, it can cause acute and chronic complications of diabetes. 1. Acute complications (1) Diabetic ketoacidosis (DKA): DKA is the most common diabetic emergency. The most common trigger is infection. Clinical manifestations are mostly nausea, headache, expiratory odor of rotten apple. The blood glucose value is mostly 16.7~33.3mmol/l. (2) Hyperosmolar hyperglycemic syndrome: the triggers can be infection, surgery, trauma and other factors. Clinical manifestations are three more and one less (more drinking, more urination, more food, weight loss) and neuropsychiatric symptoms (drowsiness, apathy, etc.), and blood glucose value is more than 33.3mmol/l. 2. Chronic complications (1) Microvascular lesions: such as diabetic nephropathy, diabetic retinopathy and so on. (2) Macrovascular lesions: such as atherosclerotic cardiovascular disease. (3) Nervous system complications: can involve the central nervous system, peripheral nerves, autonomic nerves and other corresponding complications. (4) Diabetic foot: it is one of the most serious and costly chronic complications of diabetes, and is the most important cause of non-traumatic amputation in diabetic patients. Postprandial blood glucose 30.0mmol/l, it is best to go to the hospital endocrine specialist for systematic treatment in a timely manner, and follow the doctor’s instructions to standardize the use of medication, so as not to delay the condition.