Blood sugar more than 20, generally refers to blood sugar more than 20mmol/L, whether as a pre-meal fasting blood sugar or as 2 hours after meals blood sugar, are abnormally elevated, are more serious situations, easy to cause various diseases, need to promptly seek medical treatment. Generally speaking, the normal value of fasting blood sugar is 3.9-6.1mmol/L, and the normal value of 2-hour postprandial blood sugar is 3.9-7.8mmol/L. If the blood sugar exceeds 20mmol/L, it is easy to have acute and chronic complications for a long time: 1. Acute complications: if the blood sugar exceeds 20mmol/L, it is easy to have acute complications such as ketoacidosis and hypertonic hyperglycemic syndrome. Complications. Ketoacidosis is mostly seen in young patients, and may be caused by blood glucose levels greater than 11mmol/L. Deep and fast breathing, rotten apple smell in breathing, and coma may occur in severe cases. Hyperosmolar hyperglycemic syndrome is mostly seen in elderly patients, generally blood glucose level higher than 33.3mmol/L is easy to induce, blood glucose more than 20mmol/L, but not reach 33.3mmol/L, the possibility of appearing is relatively small, can appear polydipsia, polyuria and obvious dehydration symptoms, should be admitted to hospital as soon as possible to actively control blood glucose, correct water-electrolyte imbalance, acidosis. After the disease is controlled, it is still necessary to observe the blood sugar for a long time, and use the blood sugar control drugs as prescribed by the doctor. Diabetic foot, etc. Patients may have clinical symptoms such as numbness, vision loss, and lower limb ulcers, etc. Treatment is based on blood glucose control, and the prognosis is better with strict blood glucose and blood pressure control in the early stage. Patients need to pay attention to strict control of diet in daily life, as well as low salt and low fat, proper exercise, prevention of infection, active control of blood glucose and regular medical checkup. Therefore, if blood glucose exceeds 20 mmol/L, it is recommended to consult a doctor as soon as possible and actively control blood glucose as well as symptomatic support treatment to prevent adverse consequences.