Medicare Part D Premium Disparities Highlight Growing Market Instability

Medicare beneficiaries face widening premium gaps between stand-alone prescription drug plans (PDPs) and Medicare Advantage plans (MA-PDs), with MA-PD enrollees often paying no monthly premium for drug coverage while PDPs remain significantly more expensive, according to data from the MedPAC and CMS.

Why are PDPs struggling compared to MA-PDs?

The Medicare Advantage payment system gives MA-PD sponsors a financial advantage by allowing them to retain federal rebates, which they use to subsidize Part D premiums. In 2026, MA-PD plans are projected to allocate over $600 in rebates per enrollee for drug coverage, or $53 per member per month, compared to $16 per PDP enrollee through federal subsidies. This disparity makes MA-PD plans appear “premium-free” for many beneficiaries, while PDPs face higher average monthly premiums of $44 versus $9 for MA-PDs, according to MedPAC.

Critics argue the system creates an uneven playing field. “The rebate structure for MA-PDs effectively subsidizes their drug coverage, making it harder for PDPs to compete on price,” said a CMS spokesperson. “This has contributed to a shrinking PDP market, with the average beneficiary now having 11 PDP options versus 32 MA-PD options.”

How do federal subsidies affect premiums?

The Inflation Reduction Act’s 6% cap on base premium growth and temporary PDP premium stabilization programs have prevented sharp increases but failed to close the gap. In 2026, federal subsidies reduced average PDP premiums by $53 per month, while MA-PD rebates cut premiums by $98 per month, leaving PDPs at $44 versus $9 for MA-PDs. The total cost of MA-PD rebates for drug coverage was $13 billion in 2026, 3.5 times higher than the $3.6 billion in PDP subsidies, per GAO data.

“The 6% cap helps, but it’s not enough to offset the structural advantages MA-PDs have through rebates,” said Dr. Sarah Collins, a health policy analyst at the Urban Institute. “This dynamic risks eroding choice for traditional Medicare beneficiaries.”

What are the implications for beneficiaries?

The decline in PDP availability—down from 30 to 11 options over five years—raises concerns about affordability. Nearly 80% of MA-PD enrollees pay no premium for drug coverage, compared to 28% of PDP enrollees. Low-income beneficiaries face the steepest challenges, with only two benchmark PDPs offering premium-free coverage in 2026, down from eight in 2021.

For traditional Medicare beneficiaries, the choice between PDPs and MA-PDs involves trade-offs. While MA-PDs often offer zero premiums and extra benefits, they may limit provider networks. “Rural beneficiaries, who rely more on PDPs, could see reduced access to affordable care if PDPs continue to shrink,” said a spokesperson for the AARP.

What’s next for the Part D market?

The PDP market’s instability could accelerate shifts toward Medicare Advantage, particularly among low-income and rural beneficiaries. Analysts warn that without policy changes, the disparity may deepen. “The current system favors MA-PDs, but it’s not sustainable for traditional Medicare,” said MedPAC Director Paul Ginsburg. “We need a balance that ensures access for all beneficiaries.”

As the 2026 open enrollment period approaches, beneficiaries are urged to compare plans carefully, considering both premiums and coverage details. The federal government has not yet announced new measures to address the imbalance, leaving the future of the PDP market uncertain.