Insulin is a kind of protein, which belongs to special drugs and needs special storage. Insulin can be stored at a constant temperature of 2-8℃ until the shelf life on the box, insulin cannot be frozen, and the following side effects may occur if frozen insulin is used: 1. The freezing of insulin, which is a protein, will denature the protein, leading to a weakening of the glucose-lowering effect or even the disappearance of the effect, leading to an increase in blood glucose after injection and even inducing acute complications such as diabetic ketosis or diabetic ketoacidosis. 2. Allergic reactions, insulin is a protein, and the denatured protein is more likely to have allergic reactions after freezing, with symptoms such as rash, redness and itching of the skin, and anaphylaxis can occur in severe cases. 3. The symptoms of irritation at the injection site may be aggravated by subcutaneous injection of frozen insulin, which may lead to the aggravation of irritation at the injection site, the formation of fatty hard knots at the injection site, and even fatty atrophy.