Key Facts About Medicare Part D Enrollment, Premiums, and Cost Sharing in 2025

The Medicare Part D program provides an outpatient prescription drug benefit to more than 50 million older adults and people with long-term disabilities in Medicare who enroll in private plans, including stand-alone prescription drug plans (PDPs) to supplement traditional Medicare and Medicare Advantage prescription drug plans (MA-PDs) that include drug coverage and other Medicare-covered benefits. This brief analyzes Medicare Part D enrollment and costs in 2025 and trends over time, based on data from the Centers for Medicare & Medicaid Services (CMS).

Highlights for 2025

• Enrollment in Medicare Part D stand-alone PDPs remained stable at 23 million in 2025, despite monthly premium increases in some PDPs of up to $35, the maximum increase allowed for plans participating in the Part D premium stabilization demonstration, which included measures intended to stabilize the PDP market as major changes to the Part D benefit took effect in 2025, including a new $2,000 out-of-pocket spending cap.
• Medicare Advantage continues to be the primary source of Part D drug coverage for people with Medicare, with close to 32 million enrollees. Overall, Part D enrollment is concentrated in a handful of large plan sponsors, including UnitedHealth, Centene, Humana, and CVS Health.
• Enrollment in the Part D Low-Income Subsidy (LIS) decreased in 2025, from 13.7 million to 13.1 million, the first decrease in enrollment since 2007, the first full year of the Part D program. This decrease is likely related to Medicaid disenrollment among dual-eligible individuals that stemmed from the unwinding of the Medicaid continuous enrollment provision in place during the COVID-19 pandemic
• Average monthly premiums decreased for both PDPs and MA-PDs in 2025, but the average monthly premium for Part D coverage is still substantially higher for PDPs than for MA-PDs ($39 versus $7), mainly because most MA-PD enrollees are in zero-premium plans, which is related to the ability of Medicare Advantage plan sponsors to reduce their Part D premiums using rebates, which are not available to PDP sponsors.
• Median cost-sharing amounts for drugs covered on some formulary tiers are the same or similar in PDPs and MA-PDs, but PDP enrollees are more likely than MA-PD enrollees to face coinsurance for preferred brands and non-preferred drugs, while MA-PD enrollees face higher median coinsurance for specialty tier drugs.

Part D Enrollment

Medicare Advantage drug plans continue to enroll more beneficiaries than stand-alone drug plans, but PDP enrollment has stabilized

More than half (58%) of all Part D enrollees in 2025 are in Medicare Advantage drug plans, continuing a trend of increasing enrollment in Medicare Advantage plans (Figure 1). Despite some concerns about the stability of the stand-alone PDP market as changes to the Part D benefit took effect in 2025 and an overall reduction in the number of PDPs for 2025, that decline did not result in lower overall PDP enrollment in 2025. In fact, the number of PDP enrollees has increased by 1 million since 2023. MA-PD enrollment growth was more than three times larger over the same period, however, with enrollment in MA-PDs increasing by 3.3 million between 2023 and 2025.

Part D Low-Income Subsidy enrollment is tilted even more towards Medicare Advantage drug plans than overall Part D enrollment, but overall LIS enrollment decreased in 2025

The Medicare Part D Low-Income Subsidy (LIS) provides financial assistance with drug plan premiums and cost sharing for low-income enrollees. Two-thirds of LIS enrollees – 8.8 million out of 13.1 million – are enrolled in Medicare Advantage drug plans in 2025 (Figure 2). Six million LIS enrollees are enrolled in Medicare Advantage Special Needs Plans (SNPs), nearly all of whom are in plans designed specifically for dual-eligible individuals (Table 1). LIS enrollment in MA-PDs has increased over time in tandem with overall enrollment of Medicare beneficiaries in Medicare Advantage plans.

At the same time, Part D LIS enrollment overall decreased in 2025, from 13.7 million to 13.1 million – the first decrease in enrollment since 2007, the first full year of the Part D program. This decrease is likely due to Medicaid disenrollment among dual-eligible individuals that stemmed from the unwinding of the Medicaid continuous enrollment provision in place during the COVID-19 pandemic. Medicare beneficiaries with Medicaid coverage (dual-eligible individuals) automatically qualify for LIS, meaning a loss of Medicaid coverage would lead to a loss in LIS unless eligible individuals apply and enroll separately.

Five firms cover nearly three-fourths of Part D enrollees in 2025

Part D enrollment is concentrated in a handful of top plan sponsors, with 5 firms covering 73.5% of all Part D enrollees in 2025, or 40.2 million out of 54.8 million enrollees (Figure 3). Nearly 1 in 4 enrollees (12.6 million) are in Part D plans sponsored by UnitedHealth, including both stand-alone PDPs and MA-PDs. CVS, Humana, and Centene each have around 15% of the Part D market, with enrollees in both types of Part D plans.

Centene is the top firm in the PDP market, with one-third (34%) of all PDP enrollees, followed by CVS Health (18%) and UnitedHealth (15%), while UnitedHealth is the top firm in the MA-PD market, with 29% of all MA-PD enrollees, followed by Humana (17%) and CVS Health (11%).

Nearly 5 million PDP enrollees – more than 1 in 4 – are enrolled in the lowest-premium PDP in 2025

Among the 12 national PDPs available in 2025, only one – Wellcare Value Script – has an average monthly premium less than $10 and, likely for this reason, has attracted a substantial share of all PDP enrollees, with more than 1 in 4, or 5 million, PDP enrollees in 2025 (Figure 4). Between 2024 and 2025, Wellcare Value Script gained 1.2 million PDP enrollees, as several other national PDPs experienced smaller increases and some PDPs lost enrollment, even after taking plan consolidations into account (Table 2).

The number and share of LIS enrollees in national PDPs vary considerably, which is related to the fact that only 5 of these 12 plans are benchmark PDPs, meaning they are available to Part D enrollees receiving LIS for no premium. For example, a majority of all enrollees in Wellcare Classic (83% or 2.1 million) are receiving LIS; this is a benchmark plan in 33 of 34 PDP regions (Table 3). More than two-thirds of enrollees in Cigna Healthcare Assurance Rx, a benchmark plan in 12 regions, are LIS enrollees (69% or 0.7 million). In contrast, only 3% of the 5 million enrollees in Wellcare Value Script are LIS enrollees; despite its low average premium, this is an enhanced PDP and therefore does not qualify to be a benchmark plan.

Overall, 15% (0.6 million) of the 4.2 million PDP enrollees receiving LIS (excluding those in employer group plans) are enrolled in non-benchmark PDPs. LIS enrollees in non-benchmark plans are required to pay a portion of the plan’s premium for the cost of basic benefits that exceeds the LIS benchmark amount in their region or if their plan charges a premium for enhanced benefits.

Part D Premiums

Average monthly premiums decreased for both PDPs and MA-PDs in 2025, but the average monthly premium for Part D coverage is still substantially higher for PDPs than for MA-PDs

The Part D premium demonstration for stand-alone PDPs established by the Biden administration in 2024 worked as intended to stabilize PDP premiums, with the average monthly PDP premium decreasing 9% between 2024 and 2025 from $43 to $39, despite monthly premium increases in some PDPs of up to $35, the maximum increase allowed for plans participating in the premium stabilization demonstration.

The $39 average monthly PDP premium, based on current enrollment after the end of the open enrollment season for 2025, is lower than the estimated $45 monthly PDP premium for 2025, which was based on enrollment in June 2024 and did not account for plan switching by current enrollees or plan choices by new enrollees during the open enrollment period. Taking into account plan switching and new enrollment into lower premium plans resulted in the lower enrollment-weighted average monthly premium for 2025.

On average, PDP enrollees continue to pay substantially more each month for their Part D drug coverage than enrollees in Medicare Advantage drug plans. The $39 average monthly PDP premium is nearly 6 times higher than the $7 average monthly premium for drug coverage in MA-PDs (weighted by enrollment) (Figure 5). (The total average premium for MA-PDs, including all Medicare-covered benefits, is $13 per month in 2025.) The weighted average MA-PD premium decreased by 25% between 2024 and 2025 (down from $9 to $7).

The difference between average monthly premiums for drug coverage offered by PDPs and MA-PDs has been growing larger, with the average PDP premium rising and the average MA-PD premium falling. The average premium for drug coverage in MA-PDs is heavily weighted by zero-premium plans because MA-PD sponsors can use rebate dollars from Medicare payments to lower or eliminate their Part D premiums. Rebates to Medicare Advantage plans have doubled since 2018 and now exceed $2,000 per year per beneficiary.

Eight in 10 MA-PD enrollees without low-income subsidies pay no monthly premium for Part D coverage compared to 3 in 10 PDP enrollees

Nearly 80% of MA-PD enrollees without low-income subsidies (15.1 million) pay no monthly premium for Part D coverage in 2025, compared to 31% of PDP enrollees without LIS (4.3 million). For 2025, Medicare beneficiaries had access to 29 zero-premium MA-PD plans on average, whereas only 1 PDP – Wellcare Value Script – was available for zero premium for non-LIS enrollees in most PDP regions (29 out of 34), and 6 other PDPs were available for zero premium in 5 or fewer PDP regions.

Just over half of PDP enrollees without LIS (51%) pay $30 or more – including 1 in 7 PDP enrollees without the LIS (14%) who pay at least $100 per month for their Part D plan (Figure 6). In contrast, less than 10% of MA-PD enrollees pay $30 or more per month for Part D coverage, and less than 1% pay $100 per month or more.

Out-of-Pocket Costs

Most Part D enrollees are in plans that charge a deductible for drug coverage in 2025, including 60% of MA-PD enrollees and 85% of PDP enrollees

Among MA-PD enrollees, 60% (12.3 million) are in a plan that charges a deductible for drug coverage – an increase from 2024, when only 23% of MA-PD enrollees were in a plan charging a drug deductible. In 2025, 12% of MA-PD enrollees are in a plan that charges the standard deductible of $590 (up from 3% in 2024) and 49% face a partial deductible averaging $328 (Figure 7).

A large majority of PDP enrollees (85% or 15.3 million) are in a plan that charges a drug deductible in 2025, including more than three-fourths (77%) in a plan that charges the standard deductible of $590 and 8% facing a partial deductible averaging $495. (These estimates include Part D enrollees receiving Low-Income Subsidies, who do not pay a deductible regardless of whether their plan

PDP enrollees are more likely than MA-PD enrollees to face coinsurance for preferred brands and non-preferred drugs, while MA-PD enrollees face higher median coinsurance for specialty tier drugs

As in previous years, Part D enrollees face low copayments for generic drugs and higher cost-sharing amounts for preferred brands, non-preferred drugs, and specialty drugs, regardless of whether they are in PDPs or MA-PDs (Figure 8). Median copayments for drugs covered on generic tiers are the same in PDPs and MA-PDs, but for preferred brands and non-preferred drugs, PDP enrollees are much more likely than MA-PD enrollees to pay coinsurance, or a percentage of a drug’s price. Whereas most MA-PD enrollees face a median copayment of $47 for preferred brands, most PDP enrollees face median coinsurance of 21%. For non-preferred drugs, a somewhat larger share of MA-PD enrollees face median coinsurance of 42% than a copayment of $100, while all PDP enrollees face coinsurance for non-preferred drugs, with a median rate of 40%.

Median coinsurance for specialty tier drugs (those that cost over $950 in 2025) is higher for MA-PD enrollees than PDP enrollees – 30% vs. 25%. Plans that waive some or all of the standard deductible, which most MA-PDs do, are permitted to set the specialty tier coinsurance rate above 25%.

These cost-sharing amounts apply when beneficiaries fill prescriptions in the initial coverage phase of the Part D benefit. Under a provision in the Inflation Reduction Act, beneficiaries no longer face cost sharing in the catastrophic coverage phase of the Part D benefit. In 2025, Medicare beneficiaries will pay no more than $2,000 out of pocket for prescription drugs covered under Part D.

Among the 12 PDPs offered nationwide, most charge $0 for preferred generics but only 2 charge flat copayments for preferred brands and all charge coinsurance for non-preferred drugs

Part D enrollees in 8 of the 12 national PDPs face a median copayment of $0 for preferred generics, while median copays for drugs on the standard generic tier range from $0 to $10 (Figure 9). For preferred brands, 10 of 12 national PDPs charge coinsurance, with median amounts ranging from 15% to 25%, and only 2 national PDPs charge copays. All 12 national PDPs charge coinsurance for non-preferred drugs, ranging from 31% to 50% at the median, and coinsurance for specialty tier drugs ranging from 25% to 33%.