05/20/2025

How the IRA’s Part B Coinsurance Inflation Adjustments Can Raise Seniors’ Drug Costs

The Inflation Reduction Act (IRA) is triggering increases in Medicare beneficiaries’ spending on their Part B drugs. Though CMS touts that the IRA’s inflation-based coinsurance adjustments will "lower out-of-pocket costs," the results have been more complicated. Below, we update and expand on our previous analysis.

We find that a growing number of Part B drugs now have inflation-adjusted coinsurance rates that are rising, not falling. In many cases, the rate dips temporarily before snapping back to the standard 20%. Even more troubling, these fluctuations have led to unexpected increases in patients’ out-of-pocket expenses - even when a drug’s price was declining.

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