The main complications related to long-term insulin injection are as follows: i. Weight gain, insulin is a pro-synthetic hormone, and long-term insulin injection will cause weight gain. Second, hypoglycemia, insulin is a hypoglycemic hormone, too large an injection dose or irregular diet can easily cause hypoglycemic episodes. Edema, insulin can cause sodium and water retention, resulting in edema. Allergy, insulin is a kind of protein, and insulin allergy may occur in very few patients. V. Sclerosis or fat atrophy at the injection site. Long-term subcutaneous injection of insulin can easily lead to the formation of sclerosis or fat atrophy under the skin at the injection site. Infection at the injection site. When insulin injection is not strictly disinfected or when the injection needle is repeatedly applied, it may cause infection at the injection site or even the formation of abscess.