Fatty, male, 28 years old. He was diagnosed with new-onset type 2 diabetes after a systematic examination and given dietary and exercise guidance, plus oral metformin. After taking the medicine for 3 months, Fatty’s blood sugar was ideal every time he checked, and his weight was reduced. Friends said, “Your fasting is less than 6, after meal is less than 8, glycosylated hemoglobin 5.8%, already the same as normal people”. Hearing this, Fatty thought that since it is the same as normal people, why do you think about this every day, do not dare to eat, do not dare to move, but also think about taking medicine at every meal, thinner than before, but also heard people say that metformin is harmful to the liver and kidneys, can not take long-term, and in case of hypoglycemia is said to be fatal, why not stop the drug! Without consulting the doctor, Fatty stopped the drug without permission, and began to eat and drink again without eating. A few months later, he started to feel weak and urinate more at night. The blood sugar was 10.3 mmol/L fasting, 16.1 mmol/L after meals, and 8.5% glycosylated hemoglobin. The doctor gave him the medication again and told him that repeated discontinuation of the medication caused blood sugar fluctuation, which was more detrimental to diabetic complications, and that metformin was very safe for him and would not cause hypoglycemia. Fatty listened to the doctor’s instruction and kept his blood sugar well, and stuck to his medication, not stopping it blindly on his own initiative. As we all know, good glycemic control is the only way to reduce the risk of chronic complications of diabetes, and the goal of glycosylated hemoglobin to reach 6.5% or less is the goal of glycemic control for diabetes in China as defined in the 2007 Chinese Guidelines for the Prevention and Treatment of Type 2 Diabetes. Metformin is preferred for the initial onset of type 2 obese diabetes. Metformin can effectively control blood glucose, reduce body weight, and improve insulin resistance, lower triglyceride levels, reduce fatty liver, and reduce cardiovascular events, among other effects. The UK Prospective Diabetes Study (UKPDS) and its subsequent 10-year study tell us that blood glucose control is a long and drawn-out process, and that hyperglycemic toxicity exacerbates damage to beta-cell function. Therefore, it is important to actively control blood glucose and protect the function of pancreatic islets. When the blood glucose is normal, the medication should be adhered to and the blood glucose should be monitored regularly to keep the blood glucose stable. If hypoglycemia occurs, the cause should be analyzed, and drug-induced hypoglycemia can be appropriately adjusted in medication or dose to avoid hyperglycemia caused by stopping medication after normal blood sugar. If insulin is applied, it should not be stopped easily, otherwise it will induce diabetic ketoacidosis.