Abstract
The complications of insulin self-injection include subcutaneous bleeding, nerve damage, and subcutaneous induration due to repeated injection at the same site. However, considering the short length and thinness of the needle, it is unlikely that these complications will ever become serious. Here, we report a case of a 50-year-old man with abdominal giant hematoma due to insulin self-injection, which requires surgical treatment. The patient had obesity and took anticoagulants and steroids for 12 years. These drugs seemed to have affected the vessel wall and led to its compromise or destruction and subsequent hemorrhagic events.