What drives GLP-1 prescriptions?

The recent GLP-1 prescription wave is not one trend. It combines new clinical evidence, expanded FDA indications, insurance rules, weight-management demand and the growth of products outside the approved supply chain. A 2026 analysis estimated that the March 2024 cardiovascular indication and Medicare coverage changes were associated with 592,624 additional Wegovy fills by September 2024^[1]. Coverage changed quickly. The policy-linked increase in use is not proof that access became simple or equal, that patients remained on treatment, or that the same change reached every eligible group.

The medicine at the center of that analysis was semaglutide. Wegovy was already approved for chronic weight management. In March 2024, its US indication expanded to reduce cardiovascular risk in adults with established cardiovascular disease and overweight or obesity, following the SELECT trial. Medicare Part D coverage then became possible for that additional medically accepted indication even though federal law generally excludes drugs used only for weight loss^[1][2].

Why an indication can change prescription volume

An FDA indication defines the use supported by the reviewed evidence and label. Coverage policy can then treat the same branded product differently depending on why it is prescribed and whether the patient meets the criteria. The 2026 analysis used national prescription-audit data from September 2023 through September 2024 to examine fills before and after the FDA and Medicare changes. Wegovy had the largest relative increase among semaglutide brands at 136.4%^[1].

The relative increase for Wegovy fills through Medicare Part D was 598.1%. A large percentage can start from a small base, so it should not be confused with the share of all eligible people who obtained treatment. The estimated additional-fill count also describes prescriptions dispensed, not unique patients, adherence, clinical benefit or out-of-pocket cost^[1]. One person can contribute more than one monthly fill.

The trial behind the cardiovascular indication

SELECT enrolled 17,604 adults aged 45 or older with established cardiovascular disease and a body mass index of at least 27, but no history of diabetes. Participants were randomized to semaglutide or placebo and followed for a mean of 39.8 months. Cardiovascular death, nonfatal heart attack or nonfatal stroke occurred in 6.5% of the semaglutide group and 8.0% of the placebo group. The hazard ratio was 0.80^[2].

That result supports the defined cardiovascular-risk indication. It does not mean every person with overweight qualifies, and it does not turn a prescription fill into a guaranteed avoided event. SELECT also reported adverse events leading to permanent discontinuation in 16.6% of the semaglutide group and 8.2% of the placebo group^[2]. Eligibility, contraindications, tolerability and other treatment options still need individual clinical review.

Why Medicare numbers need context

A separate 2026 study examined Medicare Part D beneficiaries starting semaglutide or tirzepatide from 2019 through 2023. Among 126,263 new users, 9.0% had no diabetes evidence under the study definition, rising to 13.8% in 2023. The authors found a 13.3 percentage-point increase from 2021 to 2023 beyond the change seen among people starting insulin^[3].

The study called this off-label prescribing, but the date window matters. It ended before the March 2024 cardiovascular indication and corresponding Medicare policy change assessed in the later fill analysis. A prescription without diabetes evidence can represent obesity treatment, another supported indication, coding gaps or use that the payer handles differently. Policy changes can reclassify part of what appears to be one continuous utilization trend.

Approved prescriptions and online products are different markets

High demand also created a parallel market for compounded and falsely labeled products. FDA says unapproved GLP-1 products do not undergo its premarket review for safety, effectiveness and quality. The agency has reported dosing errors, fraudulent labels, illegal online sales and concerns about products marketed as research use only or not for human consumption^[4]. Those products should not be counted as equivalent to a fill of an FDA-approved brand.

The distinction is easy to lose when every product is discussed under the same GLP-1 label. A prescription claim can document a dispensed branded medicine and payer, while an online transaction may not establish product identity at all and a compounded product has a separate legal and quality context. These are different markets. Policy analysis, clinical evidence and safety reporting become misleading when those supply channels are blended.

What the prescription wave does not tell us

Fill counts do not directly measure how many people wanted treatment but could not obtain it, how much they paid, how long they stayed on therapy, or whether the medicine improved their health. They also do not explain why a clinician chose one product or indication. Claims and audit data are useful for scale and timing, while clinical outcomes require different study designs.

The clearest conclusion is that evidence and coverage can change utilization quickly. The 2024 cardiovascular expansion gave some Medicare beneficiaries a covered route tied to established cardiovascular disease, and the fill data rose sharply afterward^[1]. That does not settle broader weight-loss coverage or access. Readers can review the semaglutide evidence page and its US regulatory context for the separate clinical and legal questions.

What we do not yet know

Longer follow-up is needed to show whether the added fills translated into sustained treatment and improved outcomes in routine care. Public data also need to separate indications, unique patients, repeat fills, payer decisions and product channels more clearly. Until then, a rising prescription line is evidence of changing use, not a complete account of benefit, affordability or safety.