Blood glucose 20.0mmol/L 2 hours after meal is in a relatively dangerous state and should be urgently treated in hospital, usually need to use insulin for treatment, high blood glucose can also lead to some complications, such as cardiovascular disease, dehydration coma, ketoacidosis, kidney function damage and cause eye disease, etc. 1, cardiovascular disease: blood glucose continues to appear 20.0mmol/L. can affect the normal function of cardiovascular and cerebrovascular, atherosclerosis, cerebrovascular disease, etc.; 2, dehydration coma: after meal blood sugar continues to rise, a large amount of glucose in the body with urine excretion, it will easily lead to dehydration of the body, and in serious cases, coma can occur; 3, ketoacidosis: patients with positive urine ketone bodies, the pH value of blood drops, which will lead to protein and electrolyte disorders in the body, causing diabetic ketoacidosis, and in serious cases 4, kidney function damage: high blood sugar will cause creatinine to rise, affecting the glomerular filtration rate, proteinuria, edema, to cause kidney function damage; 5, eye disease: high blood sugar will cause retinopathy, refractive changes such as myopia, hyperopia, presbyopia and cataract, and even the risk of blindness.