Diabetes patients often suffer from subcutaneous degeneration at insulin injection sites during self-administered insulin therapy (SAIT). Among the distinct types of subcutaneous complications resulting from SAIT, lipohypertrophy (LH) and insulin-derived amyloidosis (IDA) are defined as tumor-like enlargements of the adipose tissue and are caused by repeated injections at the same site. Recently, several reports have indicated that IDA is caused by an increase in the administration of insulin at the same site and is associated with poor glycemic control. The early detection and prevention of these lesions are therefore important to diabetic patients. However, these lesions are difficult to diagnose because some IDA cases are non-palpable. IDA can be detected using ultrasonography. Ultrasonography is a simple, noninvasive, and high-resolution imaging modality that is more suitable for examining subcutaneous induration as it enables the detailed observation of subcutaneous tissues without being influenced by physical conditions. Both palpable and non-palpable types of IDA can cause poor glycemic control and increase the required dose of insulin. In our study, injection sites were shifted after a subcutaneous lesion was confirmed by ultrasonography. This approach significantly decreased the necessary insulin dose and led to improvements in glycemic control. IDA leads to poor glycemic control because it impairs insulin absorption. To improve glycemic control in patients undergoing SAIT, the accurate identification of injection site induration is important. Therefore, we recommend ultrasonography for detecting non-palpable IDA. Ultrasonography should also be used to screen subcutaneous lesions in diabetes patients who are undergoing SAIT. The use of ultrasonography in clinical practice can improve diabetes care by enabling the early detection of IDA.