Lilly's tirzepatide reaches about 57% of the US GLP-1 market

Eli Lilly's tirzepatide — sold as Mounjaro for type 2 diabetes and Zepbound for obesity — now accounts for close to 57% of all US GLP-1 prescriptions, up from about 49.5% a year ago, according to IQVIA data cited by Citi analysts in a Sept. 11, 2026 update ^[1]. Novo Nordisk's semaglutide, sold as Ozempic, Wegovy and Rybelsus, stayed roughly flat over the same stretch at about 37% share ^[1].

The shift comes as the overall GLP-1 market is growing again. Using the most recent four weeks as a guide, total GLP-1 prescriptions across diabetes and obesity rose 5.4%, compared with a 6.8% decline over the same period the prior year ^[1]. Citi attributed that 12-percentage-point swing largely to the expansion of oral GLP-1 therapies, which the analysts said is likely broadening access to the drug class and pulling in new patients ^[1].

The oral pills are the swing factor

Both pills hit record weekly prescription counts in the latest reporting period. Novo's Wegovy pill reached roughly 183,000 total prescriptions, up from 181,000 the week before ^[1]. Lilly's Foundayo (orforglipron) climbed nearly 8% to 47,500 ^[1]. Citi cautioned that IQVIA may still be missing some Foundayo prescriptions written through telehealth channels, a caveat the analysts have repeated for months ^[1].

Foundayo's launch was slow out of the gate. Thirteen weeks in, it logged 19,550 weekly prescriptions — far behind the Wegovy pill's more than 105,000 at the same point, and behind Zepbound's 59,000, though ahead of injectable Wegovy's 13,000 at week 13 ^[1]. Lilly reported $98 million in Foundayo sales for the second quarter, including $67 million in the US, a figure that disappointed many analysts ^[1]. CEO David Ricks said on the earnings call that Lilly began broad direct-to-consumer advertising after securing coverage with the three largest pharmacy benefit managers in June; CVS was the last of those to add coverage, on June 1 ^[1].

Two things appear to have changed the trajectory. The Medicare GLP-1 Bridge program went live July 1, covering certain weight-loss medications, including Foundayo, for a $50 monthly copay ^[1]. And Lilly's advertising push ramped up. Ilya Yuffa, president of Lilly USA, said the company is "starting to see an inflection point on Foundayo now" ^[1].

Within Novo's franchise, the Wegovy pill has settled at about 35% of all Wegovy prescriptions, a level it has struggled to push much past ^[1]. Total Wegovy scripts, pill plus injection, ran about 513,500 in early September, while Zepbound scripts reached just under 772,000 ^[1]. In the obesity market specifically, the Lilly-to-Novo split has held near 60%–40% ^[1].

Why it matters for patients

Market share numbers are not a measure of which drug works better for any individual. But they do track things patients feel directly: what insurers cover, what pharmacies stock, and what prescribers reach for first.

The return to growth after a year of decline suggests the pills are reaching people who were not on an injectable — whether because of needle aversion, cost, supply or coverage gaps ^[1]. The Medicare Bridge program's $50 copay is one concrete access change, though it applies only to certain weight-loss medications and Part D beneficiaries ^[1].

The flip side of a widening share gap is concentration. If tirzepatide keeps taking share, more patients end up dependent on a single manufacturer's supply chain and pricing decisions. Lilly is positioning Foundayo partly on convenience — the sources note Lilly is betting that freedom from the strict fasting and water requirements that come with oral semaglutide gives its pill an edge ^[1]. Whether that translates into better real-world adherence is not addressed in the available data.

The sources do not report head-to-head efficacy, safety or side-effect comparisons behind these prescription trends, and they do not break out how much of the growth is diabetes versus obesity use. Those details are not yet known from this data.

What happens next

Citi and Jefferies publish weekly IQVIA-based prescription updates, so the share picture will keep moving ^[1]. A key open question is how much Foundayo volume IQVIA is undercounting in telehealth; Citi has flagged that it is unclear how much of recent growth reflects real demand versus better data capture ^[1]. Quarterly earnings reports from both companies — Lilly and Novo reported second-quarter results on the same day, Aug. 5, 2026 — will give a cleaner read on actual revenue ^[1]. Jefferies has said it still believes Foundayo can hit the Wall Street consensus of $1.2 billion in 2026 sales ^[1].