Medicare Part D Coverage Tightens as GLP-1 Drug Costs and Prior Authorizations Rise

A recent JAMA study reveals that Medicare Part D coverage for glucagon-like peptide-1 receptor agonists (GLP-1RAs), essential treatments for diabetes and increasingly used for weight and metabolic conditions, remains broadly available with coverage rates above 85% for key drugs in 2025. However, insurers have significantly increased access restrictions, with nearly 100% of GLP-1 prescriptions now requiring prior authorization, a sharp rise from under 5% in previous years. This trend indicates growing administrative barriers despite broad formulary inclusion.

Concurrent with increased prior authorization is a notable rise in patient out-of-pocket (OOP) costs for these medications. Average monthly OOP expenses escalated from $75-$138 in 2024 to $122-$167 in 2025, with standalone Medicare Part D plans experiencing the steepest cost increases. This cost surge aligns with a shift from flat copayments to percentage-based coinsurance models, affecting up to 77% of beneficiaries in 2025 compared to around 30% previously.

The Inflation Reduction Act's introduction of a $2,000 annual OOP cap in 2025 has influenced these dynamics by increasing insurers' financial liability for catastrophic drug expenses. Insurers appear to be offsetting these additional costs through intensified prior authorization requirements and higher patient cost-sharing. Medicare Advantage Part D plans show smaller increases in OOP costs, likely due to their capacity to manage costs through rebates and adherence incentives, unlike standalone plans.

Coverage for GLP-1RAs prescribed for non-diabetes indications remains minimal, with almost no coverage for conditions like obstructive sleep apnea or cardiovascular disease. The study notes that while formulary inclusion is widespread, actual patient access may be hindered by increasing administrative hurdles and financial barriers.

Given that GLP-1RAs rank among the highest-cost drugs in the Medicare portfolio, the study highlights ongoing challenges for insurance providers balancing budget impact with patient access and affordability. These findings underscore the complex payer strategies adjusting to new regulatory frameworks while managing high-cost specialty drug coverage.

Future scrutiny of coverage policies and cost-sharing structures is expected as Medicare plans adapt to evolving legislative mandates and market pressures. Ensuring effective management of these high-cost medications will be critical for balancing insurer financial sustainability and patient treatment accessibility in the coming years.