Diabetes mellitus (DM) is a chronic disease that requires long-term insulin therapy to control blood glucose levels. In 2019, 10,17 million people in Indonesia suffered from Diabetes Mellitus (DM), with an expected increase to 6,6 million by 2045. Non-compliance with the use of insulin can lead to serious complications. This study aimed to evaluate insulin adherence among outpatients at Dr. Moewardi Surakarta Hospital and explore the relationship between sociodemographic factors and clinical outcomes. A cross-sectional design was employed, utilizing the Morisky Medication Adherence Scale-8 (MMAS-8) and patient medical records. A total of 43 patients with diabetes mellitus participated. The findings revealed that 74.42% of patients were compliant with insulin use, while 25.58% were non-compliant. There was no significant relationship between sociodemographic factors (gender, age, education, occupation, family support, and length of illness) and patient adherence (p > 0.05). Clinical outcomes measured through HbA1c (<7%) and GDP (<130 mg/dL) targets also did not show a significant association with insulin adherence (p > 0.05). Only 28.1% of compliant patients achieved the HbA1c target, and 21.9% achieved the GDP target. Although a majority of patients demonstrated insulin adherence, achieving clinical targets was not always realized, suggesting that factors beyond adherence, such as diet and lifestyle, play a significant role in overall glycemic control.