Study Shows Insulin Cost Cap Linked to Lower and More Stable Out-of-Pocket Costs

An out-of-pocket insulin cost cap for Medicare beneficiaries was associated with lower and more stable insulin costs and increased insulin use among people with previously high insulin costs, according to an original investigation published in JAMA.

The study examined the Inflation Reduction Act’s $35 out-of-pocket cap per 30-day insulin supply for Medicare beneficiaries, which took effect in 2023. The authors assessed whether the cap was associated with changes in insulin costs and insulin use among Medicare Part D enrollees.

Researchers conducted an interrupted time series analysis using US data from January 2021 through December 2023. The study compared insulin users with Medicare Part D insurance before the cap, from 2021 to 2022, with the period after the cap took effect in 2023. Main outcomes included out-of-pocket cost per 30-day insulin supply, 30-day insulin fills, adherence measured by proportion of days covered with basal insulin, and persistence, defined as no days without basal insulin.

The study cohort included 2,860,394 insulin users with a mean age of 70.7 years, and 52% were female. In 2023, almost no insulin fills exceeded the cap, compared with 13% of fills that would have exceeded the cap in 2021 and 2022. The cost per 30-day insulin supply decreased from $22.95 before the policy to $18.16 after the policy, a 21% relative reduction. The within-year range in cost declined from $22.73 to $11.77, a 48% relative reduction.

Insulin fills, adherence, and persistence did not increase in the full cohort, but they did increase among people with high baseline insulin costs. The authors concluded that the Medicare insulin cap decreased and stabilized out-of-pocket costs and increased insulin use among people who previously had high out-of-pocket costs.

Sources: Myerson R, Kim NH, Romley J, et al. Insulin costs and use by Medicare beneficiaries after the Inflation Reduction Act out-of-pocket cap. JAMA. 2026;336(1):25-34. doi:10.1001/jama.2026.5975