Who Makes Mounjaro and Zepbound? Eli Lilly, Explained

Eli Lilly and Company (NYSE: LLY) makes both Mounjaro and Zepbound. Lilly is an American pharmaceutical company headquartered in Indianapolis, Indiana, where it has been based since its founding on May 10, 1876 ^[1][2]. Both brand names contain the same active ingredient, tirzepatide, so in that sense they are the same medicine from the same company ^[3][4][5]. The difference is what the U.S. Food and Drug Administration (FDA) has approved each brand for: Mounjaro is approved for type 2 diabetes, and Zepbound is approved for weight management and obstructive sleep apnea ^[3][4].

Lilly has also said its Lebanon, Indiana manufacturing campus is planned to make active pharmaceutical ingredient (API) for both Zepbound and Mounjaro, tying the two brands together not just in the lab but in production ^[8].

Is Mounjaro the same drug as Zepbound?

The active ingredient is the same: tirzepatide. Lilly describes Mounjaro as “the first and only FDA-approved GIP and GLP-1 receptor agonist,” meaning a single molecule that activates the body’s receptors for two incretin hormones, GIP (glucose-dependent insulinotropic polypeptide) and GLP-1 (glucagon-like peptide-1) ^[3]. Zepbound is described the same way, as “the first and only dual-activating GIP and GLP-1 obesity medication” ^[4]. Lilly has described Mounjaro and Zepbound as the only approved treatments activating two incretin hormone receptors, which is what sets tirzepatide apart from medicines that act on GLP-1 alone ^[5].

What separates them is the approved use:

	Mounjaro	Zepbound
Active ingredient	Tirzepatide [3]	Tirzepatide [4]
Approved for	Adults and children 10 and older with type 2 diabetes, with diet and exercise, to improve blood sugar; and, as of Aug. 28, 2026, to lower the risk of major adverse cardiovascular events in adults with type 2 diabetes at high risk [3]	Adults with obesity, or overweight with at least one weight-related condition, with a reduced-calorie diet and increased activity (approved Nov. 2023); and, as of Dec. 20, 2024, moderate-to-severe obstructive sleep apnea in adults with obesity [4]
Not approved for	Weight loss in the U.S. (its listed indications do not include it) [3]	Type 2 diabetes (its listed indications do not include it) [4]
Children	Not known if safe and effective under age 10 [3]	Not known if safe and effective in children [4]

Because both contain tirzepatide, the Zepbound labeling states it should not be used with other tirzepatide-containing products or with any GLP-1 receptor agonist medicine ^[4]. Lilly describes Zepbound and Mounjaro as the most prescribed injectable medicines for weight management and type 2 diabetes, respectively ^[8].

Is Eli Lilly an American company?

Yes. Lilly is a U.S. company, founded by Colonel Eli Lilly on May 10, 1876, and it has remained headquartered in Indianapolis ever since — about 150 years ^[1][2]. It trades on the New York Stock Exchange under the ticker LLY ^[3][5].

Some numbers that show the company’s current scale, all reported by Lilly itself:

• Employees: 51,168 worldwide as of June 30, 2026 — 13,583 in Indianapolis, 988 elsewhere in Indiana, 9,734 elsewhere in the U.S., and 26,863 outside the U.S. ^[2]
• 2025 revenue: $65,179 million, with net income of $20,640 million ^[2]
• Research spending: $13,337 million in 2025, or 20.5% of sales ^[2]
• Footprint: manufacturing plants in 10 countries, with products marketed in about 90 countries ^[2]

Lilly’s history in diabetes medicine goes back a long way. In 1923 it introduced Iletin, the world’s first commercially available insulin product ^[1]. Mounjaro, its next-generation incretin medicine for diabetes, came in 2022, and Zepbound was approved for chronic weight management in 2023 ^[1][4].

Why does one medicine have two brand names?

Lilly has not published an explanation of why it sells one molecule under two brand names. What the public record shows is the approval pattern: tirzepatide received separate FDA approvals under separate brand names for separate patient populations — Mounjaro for type 2 diabetes in 2022 and Zepbound for chronic weight management in November 2023 ^[1][4]. Zepbound then picked up a second approval for obstructive sleep apnea on Dec. 20, 2024, and Mounjaro picked up a cardiovascular-risk approval on Aug. 28, 2026 ^[3][4].

What evidence backs each brand’s newest approval?

Mounjaro’s Aug. 28, 2026 approval to lower cardiovascular risk came from SURPASS-CVOT, the first cardiovascular outcomes trial to compare two incretin medicines head-to-head rather than against a placebo ^[3]. It enrolled 13,299 participants across 640 sites in 30 countries, with a median follow-up of 210.1 weeks ^[3]. Participants received Mounjaro or Trulicity (dulaglutide), a GLP-1 treatment with established cardiovascular benefit — a comparison that also shows how tirzepatide was tested against a GLP-1-only medicine ^[3].

The result: Mounjaro was non-inferior to dulaglutide, with an 8% lower rate of cardiovascular death, heart attack or stroke (MACE-3). The estimated hazard ratio was 0.92 (95.3% CI: 0.83–1.01). Superiority to dulaglutide was not established ^[3].

Zepbound’s Dec. 20, 2024 approval for obstructive sleep apnea came from SURMOUNT-OSA, which randomized 469 participants to Zepbound at a maximum tolerated dose or placebo over 52 weeks ^[4]. Results:

• Adults not on PAP (positive airway pressure) therapy had 25 fewer breathing disruptions per hour on Zepbound versus 5 on placebo; adults on PAP had 29 fewer versus 6 ^[4].
• After one year, 42% of adults on Zepbound without PAP and 50% with PAP had remission or mild, non-symptomatic OSA, versus 16% and 14% on placebo ^[4].
• Weight loss averaged 45 lbs (18% of body weight) without PAP and 50 lbs (20%) with PAP, versus 4 lbs and 6 lbs (2%) on placebo ^[4].

Where are Mounjaro and Zepbound manufactured?

Lilly operates manufacturing plants in 10 countries and markets products in about 90 countries ^[2]. The company began a major manufacturing expansion in 2020, driven by tirzepatide research results, and made those investments at risk — before Mounjaro (2022) and Zepbound (2023) were approved ^[5].

Named sites in the buildout include Research Triangle Park and Concord, North Carolina; Limerick, Ireland; and Alzey, Germany, plus $1.2 billion to update existing Indianapolis facilities ^[5]. In 2024 Lilly acquired an injectable manufacturing plant in Pleasant Prairie (Kenosha County), Wisconsin from Nexus Pharmaceuticals ^[5][6]. On Dec. 5, 2024, Lilly announced a $3 billion expansion of that Kenosha County site, adding a planned 750 jobs on top of the existing 100-plus workforce, and bringing its total planned Wisconsin investment to $4 billion ^[6]. The Kenosha site will focus on injectable medicines, device assembly and packaging, and Lilly calls it its single largest U.S. manufacturing investment outside Indiana ^[6].

The Lebanon, Indiana campus is where Lilly has said it plans to make API for both Zepbound and Mounjaro ^[5][8].

When will Lilly start making medicines at its Lebanon, Indiana campus?

Lilly’s Lebanon site sits in Indiana’s LEAP Research and Innovation District in Boone County, on nearly 600 acres ^[5][7]. In its May 2024 release, Lilly said it had broken ground at the site in 2023 and expected to begin making medicines there toward the end of 2026, with operations scaling up through 2028 — a company expectation stated at the time, not a settled schedule, and not tied in the release to any specific medicine ^[5].

The investment has grown in stages:

Announcement	Amount	What it added
May 2022	$2.1 billion	Initial commitment to the site [7]
April 2023	$1.6 billion	Second round, bringing the site to $3.7 billion [7]
May 2024	$5.3 billion	Brought the site total to $9 billion [5][7]
October 2024	$4.5 billion	Lilly Medicine Foundry; site total topped $13 billion [7]
May 6, 2026	$4.5 billion	Spread across two of the three Lebanon sites; Lilly’s Indiana-wide commitments since 2020 now exceed $21 billion [8]

When Lilly announced the $5.3 billion round in May 2024, CEO David Ricks said the company believes it represents the single largest investment in synthetic-medicine API manufacturing in U.S. history ^[5]. That round was expected to add 200 full-time jobs, toward an estimated 900 full-time employees when the facility is fully operational, plus more than 5,000 construction jobs during development ^[5]. The Foundry round adds about 400 more full-time jobs ^[7].

The Lebanon campus now has three planned sites: Lilly Lebanon Advanced Therapies, which opened May 6, 2026 as the company’s first dedicated genetic medicine manufacturing facility; Lilly Lebanon API; and the Lilly Medicine Foundry ^[8]. The Foundry combines research with clinical-trial-scale manufacturing across seven main buildings and is scheduled to open in late 2027 — it is not intended for full-scale production, with new technologies instead transferred to other Lilly sites ^[7]. The May 2026 investment round also includes planned production of Foundayo (orforglipron), Lilly’s first FDA-approved GLP-1 pill ^[8].

The LEAP district as a whole has drawn $18 billion in committed capital on 2,300 acres since its 2022 launch, with Lilly the only committed company as of that report ^[7].

How big is Lilly’s overall manufacturing buildout?

As of May 2024, Lilly had committed more than $16 billion since 2020 to new U.S. and Europe sites, and more than $18 billion including the Indianapolis upgrades and the Wisconsin acquisition ^[5]. By Dec. 5, 2024, the company put its worldwide total at more than $23 billion committed since 2020 to construct, expand and acquire manufacturing sites ^[6]. Lilly says the stated purpose is to meet demand for its diabetes, obesity and pipeline medicines ^[5][6].

These are company commitments, and Lilly’s own releases note that such plans carry risks and uncertainties around cost, timing and capacity ^[6]. On supply specifically, Lilly said in 2024 that the demand crunch had eased and pharmacies were receiving much of what they ordered ^[7].

What safety information comes with both brands?

Both Mounjaro and Zepbound carry warnings that they may cause tumors in the thyroid, including thyroid cancer, and neither should be used by people with a personal or family history of medullary thyroid carcinoma (MTC) or Multiple Endocrine Neoplasia syndrome type 2 (MEN 2) ^[3][4].

Serious risks listed for both include inflammation of the pancreas (pancreatitis), low blood sugar (especially when used with a sulfonylurea or insulin), serious allergic reactions, dehydration leading to kidney problems, severe stomach problems, gallbladder problems, and food or liquid getting into the lungs during surgery or procedures involving anesthesia or deep sedation ^[3][4]. Both also list changes in vision, though the wording differs: Mounjaro’s information lists changes in vision during treatment, while Zepbound’s specifies changes in vision in patients with type 2 diabetes ^[3][4]. The Zepbound information also lists depression or thoughts of suicide, and tells patients to pay attention to mood, behavior or thought changes ^[4].

The most common side effects listed for Mounjaro are nausea, diarrhea, decreased appetite, vomiting, constipation, indigestion and abdominal pain; Zepbound’s list covers the same gastrointestinal effects and adds injection-site reactions, feeling tired, allergic reactions, belching, hair loss and heartburn ^[3][4].

Both brands note that oral birth control pills may not work as well during treatment, and a healthcare provider may recommend another type of birth control for 4 weeks after starting and for 4 weeks after each dose increase ^[3]. It is not known whether Mounjaro is safe and effective in children under 10, or whether Zepbound is safe and effective in children ^[3][4].

Side effects can be reported to the FDA at 1-800-FDA-1088 or www.fda.gov/medwatch ^[3][4]. Any question about which brand, what dose, or whether tirzepatide is appropriate belongs with a licensed prescriber.

Sources

1. Eli Lilly and Company. History: milestones of caring and discovery.
2. Eli Lilly and Company. Key facts.
3. PR Newswire. FDA approves Lilly’s Mounjaro (tirzepatide) to reduce cardiovascular risk in adults with type 2 diabetes. August 28, 2026.
4. PR Newswire. FDA approves Zepbound (tirzepatide) as the first and only prescription medicine for moderate-to-severe obstructive sleep apnea in adults with obesity. December 20, 2024.
5. Eli Lilly and Company. Lilly increases manufacturing investment to $9 billion at newest Indiana site to boost API production for tirzepatide and pipeline medicines. May 24, 2024.
6. PR Newswire. Lilly announces $3 billion expansion of its recently acquired manufacturing facility in Wisconsin. December 5, 2024.
7. Indianapolis Business Journal. Lilly to invest another $4.5B in Lebanon site for new ‘medicine foundry’.
8. PR Newswire. Lilly commits additional $4.5 billion across Indiana manufacturing sites, opens first dedicated genetic medicine facility. May 6, 2026.
9. PR Newswire. Lilly plans to more than double U.S. manufacturing investment since 2020 exceeding $50 billion. February 26, 2025.
10. US Food and Drug Administration. Declaratory order: resolution of shortages of tirzepatide injection products (Mounjaro and Zepbound). December 19, 2024.
11. Eli Lilly and Company. Lilly launches end-to-end digital healthcare experience through LillyDirect. January 4, 2024.
12. PR Newswire. LillyDirect and Walmart Pharmacy launch first retail pick-up option with direct-to-consumer pricing for Zepbound.
13. Becker’s Hospital Review. Eli Lilly weight-loss drug platform draws experts’ concern. January 10, 2024.
14. NBC News. A new weight loss drug website just launched by Eli Lilly.
15. PR Newswire. Lilly reports second-quarter 2026 financial results, raises full-year guidance, and highlights continued growth and pipeline progress.
16. US Securities and Exchange Commission. Eli Lilly and Company annual report (Form 10-K) for fiscal year 2025.