There is no so-called four major contraindications to taking insulin. The main contraindications are patients with hypoglycemia, patients who are allergic to insulin, and there are certain precautions to be taken when taking insulin, such as the need for subcutaneous injection. 1. Hypoglycemic patients: insulin can further lower the blood sugar, which can lead to the aggravation of the symptoms of hypoglycemia. 2. Patients who are allergic to insulin: some diabetic patients may be allergic to insulin, so it is forbidden to use insulin treatment to avoid adverse consequences. In the process of injecting insulin, it is necessary to pay attention to the choice of subcutaneous injection as far as possible, and also pay attention to the local disinfection measures, the operation should be standardized. Diabetic patients should be based on their own condition, under the guidance of the doctor to decide whether to apply insulin treatment, and at the same time understand the precautions related to insulin.