Growing number of unsubsidized Part D beneficiaries with catastrophic spending suggests need for an out-of-pocket cap

Medicare Part D has no cap on beneficiaries' out-of-pocket spending for outpatient prescription drugs, and, unlike Medicare Parts A and B, beneficiaries are prohibited from purchasing supplemental insurance that could provide such a cap. Historically, most beneficiaries whose annual Part D spending reached the catastrophic level were protected from unlimited personal liability by the Low-Income Subsidy (LIS). However, we found that the proportion of beneficiaries whose spending reached that level but did not qualify for the subsidy-and therefore remained liable for coinsurance-increased rapidly, from 18 percent in 2007 to 28 percent in 2015. Moreover, average total per person per year spending grew much more rapidly for those who did not qualify for the LIS than for those who did, primarily because of differences in price and utilization trends for the drugs that represented disproportionately large shares of their spending. We estimated that a cap for all Part D enrollees in 2015 would have raised monthly premiums by only $0.40-$1.31 per member.