Study Finds Increase in Medicare Part D Beneficiaries Affected by Insurers Exiting the Marketplace

Mass General Brigham researchers found that more than 7% of patients with Medicare prescription drug coverage lost their plans and had to select another plan from a different insurer in 2025

The Inflation Reduction Act (IRA), which included many changes to Medicare Part D prescription drug benefits, improved prescription drug affordability for many U.S. seniors, but also raised concerns that some insurers would exit the market. A new study from researchers at Mass General Brigham evaluates how many Medicare beneficiaries have been affected by those exits. In a paper published in JAMA, the research team reports that 2.9 million beneficiaries lost their Part D insurer between 2024 and 2025, marking a sharp increase compared to the six years prior. 

“The reforms were designed to make Part D plans better for patients — including a $2000/year out-of-pocket cap for all patients,” said senior author Benjamin N. Rome, MD, MPH, of the Program On Regulation Therapeutics, and Law (PORTAL) at Brigham and Women’s Hospital, a founding member of the Mass General Brigham healthcare system. “But these data suggest that millions of individuals who rely on Medicare prescription drug coverage could face disruptions by needing to select a plan from a different insurer.” 

For their study, the authors examined data from the Centers for Medicare & Medicaid Services from 2018 through 2024. They found that from 2018 to 2023, 0.1% to 2.3% of beneficiaries lost their Part D insurer the subsequent year. But in 2024, 7.5% of beneficiaries lost their plan the following year. The authors note that loss of coverage could encourage patients to shop for better plans. But it could also lead to disruptions in coverage and medication adherence. 

“These insurer exits will contribute to decreased competition, which may lead to decreased patient choice and eventually higher out-of-pocket costs,” said lead author Christopher L. Cai, MD, also of PORTAL. “Congress may need to take steps to stabilize the situation. This could include lowering the legal ceiling on annual deductibles, which is currently $590, or introducing a public Part D standalone option to promote competition.”

Authorship: In addition to Cai and Kesselheim, Mass General Brigham authors include Aaron Kesselheim and Anushka Bhaskar. 

Disclosures: Cai reported receiving personal fees from Alosa Health outside the submitted work. Kesselheim reported receiving personal fees from Alosa Health; and serving as an expert witness for the Federal Trade Commission for a case relating to pharmacy benefit managers, for a group of state attorneys general and payors in a case related to alleged generic drug price fixing, and for a group of payors in a case against Johnson & Johnson related to the Stelara patent outside the submitted work. Rome reported receiving personal fees from Alosa Health outside the submitted work.  

Funding: This study was funded by grants from the Commonwealth Fund and Arnold Ventures. 

Paper cited: Cai, C. L. et al. “Insurer Exits After the Inflation Reduction Act Part D Redesign” JAMA DOI: 10.1001/jama.2025.7289