OBJECTIVE | Human regular U-500 insulin (U-500R) is concentrated insulin with basal and prandial activity that can be used as insulin monotherapy. The goal of this study was to better understand treatment patterns (total daily dose [TDD] and concomitant medications), adherence, and persistence in real-world patients treated with U-500R. DESIGN AND METHODS | We selected patients from the Truven Health MarketScan database who initiated U-500R between 2010 and 2013. We collected data for three periods: pre-index (12 months before initiation), post-index (12 months after initiation or until a gap of ≥60 days in U-500R claims), and follow-up (12 months after post-index). Data were analyzed using descriptive statistics and a regression model as appropriate. RESULTS | We identified 1,582 patients who met the selection criteria. The median TDD of U-500R during the post-index period was 333 units/day, with 70.0% of patients using 300-400 units/day. During the post-index period, 74.1% of patients had U-500R claims that did not overlap with prescriptions for other insulins, interpreted as U-500R monotherapy. Among patients with ≥1 U-500R fill in the post-index period (n = 1,208), 54.4% had a medication possession ratio (MPR, a measure of adherence) ≥80%. Although 849 patients had a gap of ≥60 days in U-500R claims in the post-index period, 602 of those resumed U-500R in the follow-up period. Of the 733 patients who had no gap in U-500R claims in the post-index period, 286 had a gap of ≥60 days in claims in year 2, and 447 continued with U-500R treatment beyond 2 years. CONCLUSION | These results demonstrate that U-500R was commonly used as insulin monotherapy, with a median TDD >300 units/day. Compared with published, relevant studies of other insulins, U-500R showed similar or greater adherence and persistence rates. These new data may help guide clinical decision-making when choosing insulin therapy for patients requiring high doses of insulin.