Applying too much insulin can cause hypoglycemia, but in severe cases it can lead to death. Insulin is a protein hormone secreted by pancreatic beta cells in the pancreas stimulated by endogenous or exogenous substances, and is the only hormone in the body that lowers blood sugar. It is used for type 1 and type 2 diabetes that requires insulin therapy. For diabetic patients, insulin should be used regularly and quantitatively under the guidance of a doctor. If insulin is overdosed, it can lead to a lowering of the patient’s blood sugar, which can cause hypoglycemia. It may also lead to brain dysfunction, dizziness, drowsiness, blurred consciousness and other symptoms, and in severe cases, it may lead to brain cell necrosis or directly lead to death. For patients who need to use insulin, they should follow the doctor’s instructions and avoid increasing or decreasing the dosage on their own.