Abstract
This cross-sectional study examines Medicare Part D coverage and out-of-pocket costs for glucagon-like peptide-1 receptor agonists following implementation of the Inflation Reduction Act.
Glucagon-like peptide-1 receptor agonists (GLP-1RAs) are effective treatments for diabetes, obesity, and related conditions. Because the Inflation Reduction Act (IRA) introduced an out-of-pocket (OOP) maximum ($2000 in 2025), partly financed by increasing Part D plans’ liability from 15% to 60% of spending in the catastrophic coverage phase,1 plans may be incentivized to restrict coverage and increase cost sharing for expensive drugs, including GLP-1RAs.2,3 Although prior research investigated GLP-1RA coverage and costs,3,4 an updated analysis is warranted given the IRA’s implementation.
Methods
Using 2020 to 2025 Part D formulary files, we determined plans’ coverage of GLP-1RAs, use of prior authorization and coinsurance, and average OOP costs. Estimates were weighted by the number of plan enrollees to ensure results reflected beneficiaries’ actual exposure to each plan feature. All stand-alone Part D plans and Medicare Advantage (MA) Part D plans were included, except those missing formulary or enrollment data. We included GLP-1RAs approved for diabetes and other indications permitted by Medicare: semaglutide for cardiovascular disease (CVD) and tirzepatide for obstructive sleep apnea (OSA) (eTable in Supplement 1).
Monthly OOP costs were calculated for the pre–initial coverage limit phase (eMethods in Supplement 1). Costs reflected an average of co-payments and coinsurance, calculated by multiplying average unit costs at in-area retail pharmacies, number of units for a 1-month supply, and coinsurance percentage.
Analyses were conducted using SAS version 9.4 (SAS Institute), followed the STROBE reporting guidelines, and the study was not submitted for approval because it did not involve human participant research.
Results
In 2020, 39 566 917 beneficiaries were enrolled in 4528 plans. In 2025, 45 668 407 beneficiaries were enrolled in 5146 plans.
Coverage of most GLP-1RAs for diabetes was widespread from 2020 to 2025 (Figure, A). As of 2025, coverage rates for beneficiaries generally exceeded 85% (oral semaglutide, 84.8%; dulaglutide, 87.5%; tirzepatide, 96.2%; injectable semaglutide, 98.0%). However, brand-name liraglutide coverage declined from 96.3% in 2023 to 7.1% in 2025 upon authorized generic availability, with generic coverage of 21.1% in 2025.
Figure. Medicare Part D Formulary Coverage, Prior Authorization, Monthly Out-of-Pocket (OOP) Cost Estimates, and Coinsurance Requirements for Glucagon-Like Peptide-1 Receptor Agonists, 2020-2025a.
aAll results are weighted for beneficiary enrollment.
CVD indicates cardiovascular disease; OSA, obstructive sleep apnea.
As of 2025, coverage of GLP-1RAs for nondiabetes indications was negligible, as no beneficiaries had coverage for tirzepatide (OSA) and 1.0% had coverage for injectable semaglutide (CVD).
While prior authorization for GLP-1RAs was uncommon through 2023 (2.8%-5.0%), it was near universal in 2025 (99.9%-100.0%) (Figure, B).
OOP costs generally remained steady through 2024 but increased in 2025, rising from $75 to $138 in 2024 vs $122 to $167 in 2025 across established GLP-1RAs (Figure, C). These increases reflected rising use of coinsurance, from 27% to 36% in 2024 vs 49% to 77% in 2025 (Figure, D).
OOP cost increases were concentrated among stand-alone Part D plans (Table). For GLP-1RAs available across plan types from 2024 to 2025, costs ranged from $99 to $109 in 2024 to $175 to $196 in 2025 among stand-alone Part D plans, while costs among MA Part D plans ranged from $52 to $64 in 2024 to $93 to $101 in 2025.
Table. Trends in Medicare Part D Monthly Out-of-Pocket (OOP) Costs and Use of Coinsurance for Glucagon-Like Peptide-1 Receptor Agonists Across Plan Types, 2020-2025a,b.
| Drug name | Stand-alone Part D plans | Medicare Advantage Part D plans | ||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 2020 | 2021 | 2022 | 2023 | 2024 | 2025 | 2020 | 2021 | 2022 | 2023 | 2024 | 2025 | |
| Dulaglutide | ||||||||||||
| Monthly OOP cost, $ | 59 | 61 | 84 | 77 | 107 | 175 | 56 | 50 | 50 | 49 | 52 | 95 |
| Beneficiaries with coinsurance, % | 11.1 | 18.3 | 34.4 | 33.2 | 52.9 | 83.3 | 10.4 | 10.0 | 9.3 | 10.1 | 13.2 | 31.9 |
| Liraglutide (generic) | ||||||||||||
| Monthly OOP cost, $ | NA | NA | NA | NA | NA | 291 | NA | NA | NA | NA | NA | 194 |
| Beneficiaries with coinsurance, % | NA | NA | NA | NA | NA | 100.0 | NA | NA | NA | NA | NA | 73.2 |
| Liraglutide (brand name) | ||||||||||||
| Monthly OOP cost, $ | 62 | 70 | 101 | 86 | 285 | NA | 57 | 55 | 56 | 55 | 49 | 167 |
| Beneficiaries with coinsurance, % | 11.1 | 19.7 | 38.1 | 32.1 | 80.1 | NA | 10.1 | 10.1 | 9.6 | 10.3 | 9.0 | 76.7 |
| Semaglutide (injectable for diabetes) | ||||||||||||
| Monthly OOP cost, $ | 58 | 63 | 88 | 74 | 109 | 182 | 55 | 53 | 53 | 52 | 54 | 93 |
| Beneficiaries with coinsurance, % | 10.9 | 19.2 | 37.8 | 31.4 | 54.4 | 83.5 | 9.2 | 9.8 | 9.3 | 10.6 | 13.0 | 30.3 |
| Semaglutide (oral) | ||||||||||||
| Monthly OOP cost, $ | NA | 69 | 89 | 75 | 109 | 177 | NA | 64 | 50 | 49 | 52 | 95 |
| Beneficiaries with coinsurance, % | NA | 25.6 | 38.1 | 31.4 | 54.1 | 82.6 | NA | 16.7 | 8.6 | 10.1 | 13.3 | 31.4 |
| Semaglutide (injectable for cardiovascular disease) | ||||||||||||
| Monthly OOP cost, $ | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | 246 |
| Beneficiaries with coinsurance, % | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | 63.8 |
| Tirzepatide (for diabetes) | ||||||||||||
| Monthly OOP cost, $ | NA | NA | NA | 94 | 99 | 196 | NA | NA | NA | 80 | 64 | 101 |
| Beneficiaries with coinsurance, % | NA | NA | NA | 36.0 | 46.1 | 84.0 | NA | NA | NA | 18.9 | 15.4 | 31.9 |
Abbreviation: NA, not applicable.
All results are weighted for beneficiary enrollment. Tirzepatide (for obstructive sleep apnea) was not included because it was not covered for any Part D beneficiaries at the time of this study.
NA indicates that the drug was not available on any Part D plan formularies for the corresponding plan type and year.
Discussion
From 2020 to 2025, prior authorization for GLP-1RAs became near universal and OOP costs rose substantially in 2025, as plans increasingly required coinsurance. Although the rise in prior authorization may reflect efforts to curtail off-label GLP-1RA use, recent increases in OOP costs likely resulted from broader shifts to coinsurance affecting many high-cost drugs. This trend may have accelerated since the IRA’s Part D redesign. Consistent with prior research,2 this study found that shifts to coinsurance were most pronounced among stand-alone Part D plans. Unlike stand-alone Part D plans, MA Part D plans can leverage MA rebates to offer lower cost sharing and may benefit financially from improved adherence to GLP-1RAs, given their liability for medical and pharmaceutical costs.5
Study limitations include cost estimates that did not account for deductibles or OOP maximums. Part D beneficiaries increasingly face prior authorization and higher OOP costs to access GLP-1RAs. Although beneficiaries can avert cost increases by shopping for plans, most do not compare coverage options.6 Given the budgetary impact of GLP-1RAs for Medicare, ensuring beneficiary access and affordability will remain challenging.
eTable. GLP-1 products available in the U.S. market in early 2025 with Medicare-coverable indications
eMethods
Data Sharing Statement
References
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Associated Data
This section collects any data citations, data availability statements, or supplementary materials included in this article.
Supplementary Materials
eTable. GLP-1 products available in the U.S. market in early 2025 with Medicare-coverable indications
eMethods
Data Sharing Statement
