Insulin is used to treat diabetes. Insulin injection is a very important treatment option for diabetes, and insulin can act directly without being metabolized by the liver and kidneys. Patients with type 1 diabetes must be treated with insulin for life because of their absolute lack of insulin, and when patients with type 2 diabetes develop acute complications, they need to be treated with insulin. If a patient with type 2 diabetes cannot control blood sugar ideally after using oral medication, he or she needs to switch to insulin or add insulin combination therapy to the oral medication. Some type 2 diabetic patients with long duration of disease, poor pancreatic function, or damage to liver function or kidney function are no longer suitable for treatment with oral medication, and also need to use insulin for treatment, and gestational diabetes patients with high blood sugar also need to use insulin for treatment.