Trends in Insulin Out-of-Pocket Costs and Use Disparities, 2008-2021

To assess trends in insulin out-of-pocket (OOP) costs, use, and disparities among commercially insured patients from 2008 to 2021. Retrospective time series from a national insurance database, with members in all US states, including data from 2008 to 2021. Insulin OOP costs and 30-day equivalent fills per year were quantified among insulin users aged 12 to 64 years, stratified by income (low- vs high-poverty zip code) and health plan type (high-deductible health plans with savings options [HDHP/SO] vs not). Participants were commercially insured insulin users aged 12 to 64 years with at least 1 full enrollment year. Characteristics of interest for disparities analysis included income level (low- vs high-poverty zip code) and health plan type (HDHP/SO vs non-HDHP/SO plan). After increases in adjusted mean annual insulin OOP costs from 2008 ($221 per non-HDHP/SO member and $313 per HDHP/SO member) to 2014 ($280 and $496, respectively), HDHP/SO members had persistent relative reductions in insulin use. In 2014, HDHP/SO members had 0.17 fewer annual fills, a disparity that increased until 2019 (0.79) before decreasing slightly by 2021 (-0.55). Lower-income members consistently had fewer insulin fills. Insulin OOP cost reduction policies would be more efficient if they targeted HDHP/SO plan members and low-income patients.