Out-of-pocket insulin spending before and after the Inflation Reduction Act across demographic subgroups

Introduction: The Inflation Reduction Act (IRA) capped out-of-pocket (OOP) insulin spending at $35 for Medicare Part D beneficiaries in 2023. Studies have shown lower per-prescription insulin spending after the IRA but less is known about annual OOP insulin spending. We examined whether beneficiaries' annual insulin spending fell below $420 (ie, $35/month) and whether savings differed across demographic subgroups. Methods: Using nationally representative data from the Medical Expenditures Panel Survey, we estimated survey-weighted two-part models comparing annual per-person OOP insulin spending in 2022 and 2023 overall, and by sex, race and ethnicity, income, education, insurance type, and number and type of insulin prescriptions. Results: Annual per-person OOP spending on insulin decreased from $359.95 in 2022 to $214.11 in 2023 (P = 0.016). However, 13.2% of Part D beneficiaries spent more than $420 in 2023, and rates of cost-related medication nonadherence were unchanged. Reductions in spending were consistent across demographic subgroups. Conclusion: The IRA's universal cap on insulin for Medicare beneficiaries was associated with reductions in annual OOP spending across demographic subgroups, highlighting its potential to improve equitable access to insulin. However, persistent spending above the annualized cap for 1 in 7 patients suggests gaps in protection and the need for additional solutions.