Lilly publishes an open letter attacking insurers that drop obesity coverage

Eli Lilly published an open letter on May 21, 2025, arguing that insurance companies and pharmacy benefit managers are forcing people with obesity to make an unfair choice: stop taking a medicine that is working for them, or pay full price to stay on it ^[1]. The letter does not name a specific insurer or PBM, but it comes after a recent formulary change that altered which obesity drug some patients could get covered ^[1].

Lilly's letter lays out several positions. It says coverage decisions should be based on clinical evidence and left to health care providers and patients, not dictated by rebate arrangements between drugmakers and payers ^[1]. It also points out that Medicare does not cover any obesity management medications at all, and only a small number of states cover them under Medicaid ^[1]. Even when a PBM adds an obesity drug to its formulary, Lilly notes, employers must separately opt in to cover it, and many do not ^[1].

Lilly frames this as a systemic problem, not a single-formulary dispute. The company says these payer-driven switches "undermine a health care provider's ability to choose the most appropriate treatments" and can leave patients with related conditions, such as obstructive sleep apnea, without a workable medicine or facing high out-of-pocket costs to stay on their current one ^[1]. The letter states four commitments: support for open access to obesity drugs according to their labeled use, coverage based on clinical evidence, willingness to offer new pricing arrangements to insurers and employers, and a call for obesity treatment to be covered the same way other chronic disease treatments are ^[1].

The development summary describing this story notes that Novo Nordisk later made a similar argument in reverse when the coverage situation flipped in its favor roughly a year afterward. That later episode, including its exact wording and timing, is not detailed in the source material reviewed for this article, so specifics of Novo's letter are not yet known from what is available here.

Why it matters for patients

For people currently taking Zepbound (tirzepatide) or Wegovy (semaglutide), this letter is a sign that which drug your insurance covers can change with little warning, often tied to rebate deals between drugmakers and pharmacy benefit managers rather than a change in medical evidence ^[1]. Lilly's letter says these switches can force patients to stop a medicine that is working, switch to a different one, or pay out of pocket ^[1].

The letter also highlights a coverage gap that affects far more people than any single formulary dispute: Medicare does not pay for obesity drugs at all, and Medicaid coverage exists in only a handful of states ^[1]. Even employer-sponsored plans that technically list an obesity drug on their formulary may not have opted in to actually cover it ^[1]. That means access can depend heavily on where someone lives, who their employer is, and which PBM their plan uses, separate from any single company's public dispute with an insurer.

What happens next

Lilly's letter, published May 21, 2025, calls on "health care, government and others in the industry" to pursue evidence-based obesity coverage policies, but it sets no specific deadline or regulatory target ^[1]. The letter directs affected patients to resources on Lilly's Zepbound access website for help navigating coverage changes ^[1]. Whether insurers, PBMs, or employers change their formulary practices in response, and what Novo Nordisk's later mirror-image argument specifically said, are not established in the sources reviewed here.