There are certain side effects of insulin for diabetic patients: 1. The biggest side effect of insulin is hypoglycemic reaction. If the amount of insulin injected is too large, or if the dose of insulin is not adjusted correctly, and if the patient does not eat in time after the insulin injection, including the patient’s lifestyle is not fixed and exercise is not standardized, hypoglycemic reactions can occur. Severe hypoglycemic reactions can also lead to the occurrence of sequelae and side effects such as hypoglycemic coma. 2.Side effects of insulin and secondary sodium and water retention can occur. 3. Insulin can also cause allergic side effects, such as redness, swelling, rash, papules, herpes and blisters around the skin where insulin is injected. 4, insulin can also cause secondary weight gain after taking insulin for too long, which is also a side effect of insulin. However, you should not refuse to use insulin because of the fear of side effects, and the specific glucose-lowering drug program should be carried out under the guidance of a specialist.