How Long People Stay on GLP-1s

Every ROI model, every budget projection, every coverage decision depends on how long members stay on GLP-1 therapy. If persistence is high, the cost per outcome may be justifiable. If it's low, most of the pharmacy spend generates no lasting clinical benefit — members discontinue before reaching meaningful weight loss and regain whatever they lost.

The published data on GLP-1 persistence is extensive but deeply conflicting. Reported 12-month rates range from 10% to 63% depending on the source. This isn't because some studies are wrong. It's because they measure different things, in different populations, at different time periods, using different definitions of what counts as "still on therapy." A study counting every prescription attempt — including those rejected by insurers — produces a fundamentally different number than one tracking only patients who filled at least one prescription during a post-shortage era.

This page compiles every published data point, explains why the numbers differ, and identifies which estimates are most relevant for different planning scenarios. For financial modeling, cross-reference with the costs page.

Even in Samuels et al.'s no-cost academic obesity clinic, 12-month persistence reached only ~50%, suggesting that cost removal alone cannot close the gap entirely. Clinical trial infrastructure — frequent monitoring visits, dose titration support, patient engagement protocols — accounts for a substantial portion of the remaining difference. Trial discontinuation is driven primarily by adverse events (4–17%), while real-world discontinuation is driven by cost/insurance (48%), side effects (15–23%), and supply shortages (8–12%).

Three factors likely drive the improvement. First, supply shortage resolution is the primary driver — Wegovy entered the FDA's shortage list in March 2022 and semaglutide shortages persisted through 2023. Second, tirzepatide (Zepbound) availability from November 2023 introduced a second high-potency option with high initial persistence (~64%) and a switching target for patients struggling with semaglutide tolerability. Third, improved clinical management — better dose titration protocols, GI side-effect management, and care programs — may contribute, though this is harder to quantify from claims data alone.

Among non-T2D patients who discontinued, 36.3% reinitiated within 1 year (Rodriguez et al., 95% CI: 35.6–37.0%). For T2D patients, the reinitiation rate was higher at 47.3%. Weight regain was the strongest driver: each 1% of weight regained increased the hazard of reinitiation by 2.8%.

Gasoyan et al. found that among discontinuers, 19.6% restarted the same medication within 1 year while 35.2% received some alternative obesity treatment (27.4% a different medication, 13.7% lifestyle visits, 0.6% bariatric surgery). Among obesity-only patients, the restart rate was lower at 14.2% — roughly half the diabetes restart rate (23.5%), consistent with insurance coverage barriers.

Post-discontinuation weight trajectories are less catastrophic than trial withdrawal data suggests. While the STEP 1 extension showed participants regained two-thirds of lost weight within 1 year of stopping, the Cleveland Clinic real-world data found obesity patients lost an average of 8.4% before stopping but regained only 0.5% at 1 year post-discontinuation. The explanation: real-world patients stop earlier and at lower doses, losing less weight to begin with and potentially adopting compensatory lifestyle behaviors. (For the full weight regain evidence, see What Happens When People Stop GLP-1s.)

No study tracks outcomes beyond the first reinitiation event. The dominant real-world utilization pattern appears to be cycling (start → stop → regain → restart), but its cost-effectiveness is unmeasured. Each restart involves dose re-escalation (~16 weeks), new prior authorizations, and repeated clinical engagement costs.

The 37.5% mean PDC at 3 years means the average patient had medication on hand for roughly 410 of 1,095 days — just over one-third of the time. By 3 years, adherence (12.5%) actually exceeds persistence (8.1%) because PDC captures partial medication coverage from patients who eventually stopped, while persistence is an all-or-nothing measure. These figures paint a picture of widespread intermittent use rather than clean binary adherence or discontinuation.

No multi-year data exists for post-shortage cohorts. The encouraging 62.6% 12-month persistence from 2024 initiators has no 24- or 36-month follow-up. Whether the steep attrition seen in 2021 cohorts will repeat or whether newer cohorts sustain gains is unknown.

Cycling outcomes are unmeasured. The dominant real-world pattern — start, stop, regain, restart — has no published cost-effectiveness or health outcomes data. No study tracks what happens after the second or third course of treatment.

Compounded semaglutide creates a blind spot. All claims-based studies cannot capture compounded GLP-1 use or cash-pay purchases. Patients appearing "non-persistent" in claims data may have continued therapy through these channels.

No randomized evidence compares benefit design strategies. Whether low copays, mandatory counseling, step therapy, or coverage duration limits optimize persistence-adjusted ROI has not been studied in controlled settings.

The Prime trend data is unreplicated. The most important finding on this page — persistence doubling from 2021 to 2024 — comes from a single PBM's commercially insured book. No other source has published year-by-year cohort trends.

Optimal treatment duration is undefined. The question "how long must a patient stay on therapy to achieve durable clinical benefit?" has no definitive answer.

Clinical trial populations don't match employer populations. Trial participants were screened, motivated, and received free medication with frequent monitoring. Extrapolating trial efficacy to a broad commercial population requires discounting by persistence, adherence, dose attainment, and patient selection — a compound discount that is rarely quantified.

Persistence means continuous treatment without a gap exceeding a defined threshold — most commonly 60 days. A patient who fills their prescription every 4 weeks with no gaps longer than 60 days is "persistent." The moment they go 60+ days without a fill, they are classified as having discontinued, even if they restart later.

Adherence is measured as proportion of days covered (PDC) — the number of days with medication on hand divided by the observation period. PDC ≥80% is the standard threshold for "adherent." Unlike persistence, adherence is a continuous measure (0–100%) and captures partial use.

The 60-day gap is the most common standard in published GLP-1 persistence research. Some studies use different thresholds (Do et al.: 135-day; BHI: 2× expected Rx duration; Gasoyan: 90-day). These definitional differences explain much of the variance in reported rates and are flagged throughout this page.

Switching between GLP-1s should generally count as persistence for employer modeling purposes — switching from Wegovy to Zepbound is not discontinuation from the employer's perspective. Most studies in the master table allow switching; those that don't are noted.

Source quality hierarchy: ★★★★ = peer-reviewed journal with disclosed methods; ★★★ = PBM report or white paper with methods disclosed; ★★ = conference presentation or poster; ★ = industry blog or news article with undisclosed methodology. Where sources conflict, higher-quality sources are given greater weight in summary statements.

All data is drawn from publicly available sources. Conflicts between sources are flagged rather than resolved. Gaps are noted as gaps. This page is reviewed and updated as new data becomes available. Corrections can be submitted via the contact page.