Patients with diabetes often ask: Do I have to use insulin? When should I apply insulin? These questions may seem simple, but they are not easy to answer. This article briefly describes these common questions as follows. Who must use insulin? Type 1 diabetes: lifelong application Type 1 diabetes used to be called “insulin-dependent diabetes” because this type of patient completely loses the function of insulin secretion and must rely on insulin to maintain life. Some patients are prone to take the meaning of the word “insulin-dependent” and think that insulin dependence is as terrible as drug addiction, which makes them afraid to start insulin therapy easily. In this regard, patient education should be strengthened. Tip: “Insulin-dependent diabetes” does not refer specifically to type 1 diabetes, but also includes type 2 diabetes with a long history of islet beta cell failure. Some community physicians say that Latent Immune Diabetes Mellitus in Adults (LADA) also belongs to “insulin-dependent diabetes”, which is correct, but it should be noted that LADA itself is a subtype of type 1 diabetes. Type 2 diabetes: those with long duration of the disease and those with poor control of the disease need to apply Type 2 diabetes includes two kinds of conditions: first, the body insulin level is significantly reduced; second, insulin insensitivity and relative lack of insulin. Since the body can still secrete insulin, this type of diabetes was also called “non-insulin-dependent diabetes” in the past. However, insulin therapy is also necessary for the overall course of type 2 diabetes. Most patients with “long-standing” type 2 diabetes require insulin therapy. As the disease progresses, both fasting blood glucose and postprandial blood glucose gradually increase, while beta cell function as a whole gradually decreases. Therefore, insulin supplementation therapy is always needed in the later stages as long as the duration of diabetes is long enough. Long-term observation of type 2 diabetic patients reveals that most patients cannot control blood glucose by oral hypoglycemic drugs alone after 8 to 10 years of illness, and at this time, if insulin is not used, it is difficult to get satisfactory control of blood glucose, and the diabetic complications caused by high blood glucose will progress significantly. Therefore, from the perspective of reducing complications and prolonging the patient’s life, insulin must also be used when the disease progresses to a certain stage. Tips: Patients may have endogenous insulin deficiency: (1) low weight patients who are lean; (2) patients who were originally fat or normal weight and have recently experienced significant weight loss; (3) significant hyperglycemia; (4) large fluctuations in blood glucose; (5) non-starvation ketosis. Patients with “multimorbidity” This includes 2 conditions: First, other diseases or conditions that may cause fatal metabolic disorders, such as patients with diabetes requiring major surgery, severe trauma, or severe infection, who may develop ketosis, ketoacidosis, or non-ketotic hyperosmolar coma, which can be life-threatening. Second, other diseases can cause oral hypoglycemic drug accumulation poisoning. For example, patients with hepatic or renal insufficiency or severe hypoxia f such as heart failure), because of poor metabolism of oral hypoglycemic drugs in the body, can cause drug accumulation and aggravate adverse reactions. Insulin is a natural substance in living organisms and is the safest drug among all the current glucose-lowering drugs. Diabetic patients should not hesitate to receive insulin therapy when it is needed. Although oral hypoglycemic drugs can control high blood sugar in pregnant women with diabetes, there is no evidence from clinical trials on whether the drugs have adverse effects on the fetus. Insulin, on the other hand, is a natural hormone in living organisms, and its safety is reliable. Therefore, when the blood sugar of pregnant women with diabetes is so high that it cannot be controlled by diet and exercise, insulin must be used to control the blood sugar and ensure the safety of mother and baby.