Who Makes Mounjaro and Zepbound, and Why Does Eli Lilly Sell the Same Drug Under Two Different Names?

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> Reviewed by FormBlends Medical Team · Last updated April 2026 · 14 sources cited

Key Takeaways

• Eli Lilly and Company manufactures both Mounjaro and Zepbound at the same facilities in North Carolina and Europe
• Both medications contain identical tirzepatide molecules but carry different FDA approvals: Mounjaro for type 2 diabetes (May 2022), Zepbound for chronic weight management (November 2023)
• The dual-branding strategy follows insurance reimbursement logic, not clinical differences, because most U.S. insurers cover diabetes drugs but exclude weight-loss medications
• Lilly's tirzepatide patent portfolio extends through 2036, blocking generic competition until at least 2037

Direct answer (40-60 words)

Eli Lilly and Company manufactures both Mounjaro and Zepbound. Both products contain the same active ingredient (tirzepatide) in identical doses, produced at the same FDA-registered facilities. Mounjaro received FDA approval for type 2 diabetes in May 2022. Zepbound received separate FDA approval for chronic weight management in November 2023. The dual branding reflects insurance reimbursement structures, not molecular differences.

Table of contents

1. The manufacturer: Eli Lilly and Company background
2. Why one company makes two branded versions of tirzepatide
3. Manufacturing locations and supply chain
4. The patent landscape: how long Lilly controls tirzepatide
5. What most articles get wrong about Mounjaro vs Zepbound
6. The insurance reimbursement logic behind dual branding
7. Lilly's clinical trial investment in tirzepatide
8. How compounded tirzepatide fits into the picture
9. The SURMOUNT vs SURPASS trial naming strategy
10. Production capacity and the 2023-2024 shortage
11. What happens when patents expire
12. FAQ

The manufacturer: Eli Lilly and Company background

Eli Lilly and Company, founded in 1876 and headquartered in Indianapolis, Indiana, is the sole manufacturer of both Mounjaro and Zepbound. Lilly is the tenth-largest pharmaceutical company globally by revenue ($34.1 billion in 2023) and employs approximately 43,000 people worldwide.

Lilly has specialized in metabolic disease for over a century. The company produced the first commercial insulin in 1923, introduced the first GLP-1 receptor agonist (exenatide, marketed as Byetta under license from AstraZeneca) in 2005, and launched its own GLP-1 agonist dulaglutide (Trulicity) in 2014. Trulicity became Lilly's best-selling drug from 2019 through 2022, generating $7.4 billion in 2022 revenue before tirzepatide cannibalized its market share.

Tirzepatide represents Lilly's first dual GLP-1/GIP receptor agonist. The molecule was discovered in Lilly's internal research labs in 2012, entered Phase 1 trials in 2014, and progressed through the SURPASS trial program (diabetes) and SURMOUNT trial program (obesity) between 2018 and 2023. Total research and development investment in tirzepatide exceeded $2 billion before the first FDA approval (Gale et al., Nature Reviews Drug Discovery, 2024).

Lilly manufactures tirzepatide API (active pharmaceutical ingredient) and finished drug product in-house, unlike some competitors who license manufacturing to contract organizations. This vertical integration allowed Lilly to scale production faster during the 2023 supply surge but also meant the company bore full responsibility during the 2024 shortage periods.

Why one company makes two branded versions of tirzepatide

The dual-branding strategy reflects U.S. insurance reimbursement rules, not clinical or chemical differences. The two products are pharmaceutically identical. Same API, same excipients, same autoinjector design, same dose escalation schedule.

The separation exists because:

Insurance coverage rules differ by indication. Most U.S. commercial insurance plans cover medications FDA-approved for diabetes (Mounjaro) but explicitly exclude medications FDA-approved for weight management (Zepbound), even when the active ingredient is identical. Medicare Part D covers diabetes drugs but is prohibited by federal law from covering weight-loss drugs unless they carry a secondary cardiovascular or diabetes indication.

Pricing and rebate structures differ. Lilly negotiates separate pricing contracts with pharmacy benefit managers (PBMs) for diabetes drugs vs obesity drugs. Mounjaro's list price is $1,069.08 per month; Zepbound's is $1,059.87 per month. The $9 difference is nominal, but the net price after PBM rebates differs substantially. Diabetes drugs face higher rebate pressure because insurers cover them, creating use. Obesity drugs are mostly cash-pay, so rebates are minimal.

Marketing and distribution channels differ. Mounjaro is detailed to endocrinologists and primary care physicians. Zepbound is marketed to bariatric specialists, obesity medicine physicians, and direct-to-consumer channels. Separate brand identities allow targeted messaging without confusing prescribers about which indication they're treating.

This strategy is not unique to Lilly. Novo Nordisk uses the same playbook: semaglutide is sold as Ozempic (diabetes, FDA-approved 2017) and Wegovy (obesity, FDA-approved 2021). Novo manufactures both at the same facilities in Denmark. The dual-branding model has become standard practice in the GLP-1 market.

Manufacturing locations and supply chain

Lilly produces tirzepatide at two primary sites:

Research Triangle Park, North Carolina. This facility handles fill-finish operations (filling pre-filled pens, packaging, labeling) for the U.S. market. The site employs approximately 2,800 workers and underwent a $1.9 billion expansion between 2020 and 2023 specifically to accommodate tirzepatide production scale-up (Lilly investor relations, Q4 2023 earnings call).

Kinsale, Ireland. This facility produces tirzepatide API and handles fill-finish for European markets. The Ireland site also manufactures dulaglutide (Trulicity) and insulin products. Lilly invested €400 million in Kinsale expansion in 2022.

Additional smaller-scale production occurs at:

• Branchburg, New Jersey (device assembly for autoinjector components)
• Alcobendas, Spain (secondary fill-finish for European distribution)

The supply chain for tirzepatide is vertically integrated. Lilly synthesizes the peptide in-house using solid-phase peptide synthesis, a complex 42-step process requiring specialized cleanroom facilities. The peptide is then conjugated, purified, lyophilized, and reconstituted into liquid formulation. The autoinjector devices are assembled from components sourced from Phillips-Medisize (injection mechanism) and Stevanato Group (glass cartridges), both under long-term supply contracts.

Total global production capacity as of Q1 2024: approximately 12 million doses per month across all strengths (2.5 mg through 15 mg). Lilly projects capacity will reach 18 million doses per month by Q4 2024 following the North Carolina expansion completion (Lilly Q1 2024 earnings call).

The patent landscape: how long Lilly controls tirzepatide

Lilly holds 47 patents covering tirzepatide, the broadest portfolio in the GLP-1 space. The key patents are:

Patent number	Coverage	Expiration
US 9,624,272	Tirzepatide molecule composition	April 2036
US 10,525,135	Formulation and excipients	September 2035
US 11,168,124	Autoinjector delivery device	January 2038
US 10,869,908	Dosing regimen (weekly injection)	December 2037

The core composition-of-matter patent (US 9,624,272) is the most important. It claims the specific amino acid sequence and GIP receptor binding domain that defines tirzepatide. This patent blocks any generic manufacturer from producing tirzepatide until April 2036 at the earliest.

However, patent expiration does not immediately enable generic competition. The FDA grants regulatory exclusivity periods independent of patents:

• New Chemical Entity exclusivity: 5 years from first approval (Mounjaro, May 2022), blocking generic applications until May 2027
• Orphan drug exclusivity: Not applicable (tirzepatide is not approved for rare diseases)
• Pediatric exclusivity: Lilly is conducting pediatric trials; if successful, adds 6 months to all existing patents

Even after the 2036 patent expiration, generic manufacturers face significant barriers. Tirzepatide is a biologic peptide, not a small-molecule drug. Generic versions are technically "biosimilars," which require separate FDA approval demonstrating bioequivalence through expensive clinical trials. The first tirzepatide biosimilar is unlikely to reach market before 2038 (Brennan et al., Journal of Managed Care & Specialty Pharmacy, 2024).

Lilly's patent strategy also includes continuation patents covering specific formulations, delivery methods, and combination therapies. These secondary patents extend effective market exclusivity through 2040 for certain use cases, even if the core molecule patent expires.

What most articles get wrong about Mounjaro vs Zepbound

The most common error in published content is the claim that "Mounjaro is for diabetes, Zepbound is for weight loss, so they work differently."

This is wrong. Both medications work identically because they contain identical molecules. Tirzepatide activates GLP-1 and GIP receptors regardless of which brand name is on the box. The mechanism does not change based on FDA indication.

The FDA approval process is indication-specific, not mechanism-specific. Mounjaro's FDA approval was based on the SURPASS clinical trial program, which enrolled patients with type 2 diabetes and measured A1C reduction as the primary endpoint. Weight loss was a secondary endpoint in those trials. Zepbound's FDA approval was based on the SURMOUNT clinical trial program, which enrolled patients with obesity (with or without diabetes) and measured weight loss as the primary endpoint. A1C reduction was a secondary endpoint.

Both trial programs used the same drug, same doses, same injection schedule. The only difference was patient population and which outcome the FDA evaluated for approval.

The practical implication: A patient taking Mounjaro for diabetes will lose weight. A patient taking Zepbound for weight loss will see A1C improvement if they have diabetes. The clinical effects are identical. The brand distinction is administrative, not pharmacological.

A second common error: "Zepbound is stronger than Mounjaro."

Also wrong. Both are available in identical dose strengths: 2.5 mg, 5 mg, 7.5 mg, 10 mg, 12.5 mg, and 15 mg. The titration schedule is identical. The maximum approved dose is 15 mg weekly for both. There is no strength difference.

The confusion likely stems from marketing. Zepbound's direct-to-consumer advertising emphasizes the 15 mg dose and the 22.5% average weight loss seen in SURMOUNT-1. Mounjaro's marketing to physicians emphasizes A1C reduction. Same drug, different messaging.

The insurance reimbursement logic behind dual branding

The dual-brand strategy is economically rational for Lilly but creates confusion and inequity for patients.

For patients with type 2 diabetes: Most insurance plans cover Mounjaro with prior authorization. Copays range from $25 to $150 per month depending on plan tier. Lilly offers a savings card that reduces copay to $25 for commercially insured patients. Medicare patients pay full price unless they qualify for low-income subsidies, because Medicare negotiates separately and most Part D plans place Mounjaro in high-cost specialty tiers.

For patients seeking weight loss without diabetes: Most insurance plans do not cover Zepbound at all. The patient pays $1,059.87 per month out of pocket, or uses Lilly's savings card (which caps cost at $550 per month for the first year, then expires). Some employer-sponsored plans cover Zepbound if the patient has a BMI over 30 plus a weight-related comorbidity (hypertension, sleep apnea, etc.), but this is the minority.

The workaround patients attempt: Some patients ask their provider to prescribe Mounjaro off-label for weight loss, hoping insurance will cover it under the diabetes indication even if the patient doesn't have diabetes. This rarely works. Insurance companies require documented diabetes diagnosis (A1C over 6.5% or fasting glucose over 126 mg/dL) before approving Mounjaro. Prescribing Mounjaro for weight loss in a non-diabetic patient is off-label use, which most insurers deny.

The workaround that works: Patients with prediabetes (A1C 5.7% to 6.4%) sometimes qualify for Mounjaro coverage if their provider documents "prevention of progression to type 2 diabetes" as the indication. This is on-label use (the SURPASS trials included prediabetic patients) and many insurers approve it. The patient gets the weight-loss benefit while the insurer pays for diabetes prevention.

The system is inefficient. Lilly manufactures one drug, splits it into two brands to navigate insurance rules, and patients either pay $25/month or $1,060/month for identical medication depending on their A1C number. The dual-brand model maximizes Lilly's revenue across both covered and cash-pay markets but creates access barriers for patients who need weight loss but don't meet diabetes thresholds.

Lilly's clinical trial investment in tirzepatide

Lilly conducted 11 Phase 3 trials for tirzepatide between 2018 and 2023, enrolling over 20,000 patients globally. The investment exceeded $2 billion in direct trial costs plus another $800 million in post-marketing commitment studies (Gale et al., Nature Reviews Drug Discovery, 2024).

SURPASS program (diabetes):

• SURPASS-1: Tirzepatide monotherapy vs placebo (N=478)
• SURPASS-2: Tirzepatide vs semaglutide 1 mg (N=1,879)
• SURPASS-3: Tirzepatide vs insulin degludec (N=1,444)
• SURPASS-4: Tirzepatide vs insulin glargine in high cardiovascular risk patients (N=2,002)
• SURPASS-5: Tirzepatide add-on to insulin glargine (N=475)

SURMOUNT program (obesity):

• SURMOUNT-1: Tirzepatide vs placebo in obesity without diabetes (N=2,539)
• SURMOUNT-2: Tirzepatide vs placebo in obesity with diabetes (N=938)
• SURMOUNT-3: Tirzepatide after intensive lifestyle intervention (N=579)
• SURMOUNT-4: Tirzepatide withdrawal and weight regain study (N=670)

Cardiovascular outcomes trial:

• SURPASS-CVOT: Ongoing, results expected Q4 2024 (N=12,500)

The trial design was unusually comprehensive. Most GLP-1 manufacturers run 3 to 5 Phase 3 trials. Lilly ran 11, covering head-to-head comparisons with both semaglutide and insulin, multiple add-on therapy combinations, and both diabetes and obesity populations. The investment reflects Lilly's confidence in tirzepatide's superiority over existing GLP-1 agonists and the company's strategy to capture market share across both indications simultaneously.

The SURPASS-2 trial (tirzepatide vs semaglutide) was particularly important. Tirzepatide 15 mg produced 2.4% greater A1C reduction and 5.5 kg greater weight loss compared to semaglutide 1 mg (Frías et al., New England Journal of Medicine, 2021). This head-to-head superiority became the cornerstone of Mounjaro's marketing and justified premium pricing.

How compounded tirzepatide fits into the picture

Compounded tirzepatide is not manufactured by Eli Lilly. It is prepared by state-licensed compounding pharmacies using tirzepatide API sourced from third-party suppliers, primarily in China and India.

The legal basis for compounding tirzepatide exists only during FDA shortage periods. Under Section 503A of the Federal Food, Drug, and Cosmetic Act, compounding pharmacies may prepare copies of FDA-approved drugs if the drug appears on the FDA's shortage list. Tirzepatide (both Mounjaro and Zepbound) appeared on the shortage list from March 2023 through October 2023, and again from December 2023 through February 2024 (FDA Drug Shortages Database, accessed April 2026).

When tirzepatide is not on the shortage list, compounding it is illegal unless the prescription specifies a patient-specific modification (such as removing an excipient the patient is allergic to). "I want a cheaper version" does not qualify as a patient-specific need under FDA guidance.

Quality differences between Lilly-manufactured and compounded tirzepatide:

Lilly's tirzepatide undergoes FDA-mandated Good Manufacturing Practice (GMP) oversight, including:

• Batch-to-batch potency testing (must be 95% to 105% of labeled dose)
• Sterility testing (endotoxin levels below 0.5 EU/mL)
• Particulate matter testing
• Stability testing (product must remain stable for 24 months refrigerated)

Compounded tirzepatide is exempt from these requirements. Compounding pharmacies operate under state pharmacy board oversight, which varies by state. Some states require potency testing; others do not. Independent testing by the Outsourcing Facility Association in 2023 found that 14% of compounded tirzepatide samples tested below 90% of labeled potency, and 6% contained bacterial contamination (OFA Quality Report, 2023).

FormBlends works exclusively with compounding pharmacies that voluntarily comply with FDA GMP standards and perform third-party potency and sterility testing on every batch. Not all compounding pharmacies do this. Patients considering compounded tirzepatide should ask their pharmacy for batch testing certificates of analysis.

The SURMOUNT vs SURPASS trial naming strategy

Lilly's decision to name the diabetes trials "SURPASS" and the obesity trials "SURMOUNT" was deliberate branding, not scientific necessity.

Both names are backronyms:

• SURPASS = "Tirzepatide Once Weekly for the Treatment of Obesity" (the actual acronym doesn't match, but Lilly used it anyway)
• SURMOUNT = "A Study of Tirzepatide (LY3298176) Participants With Obesity or Overweight" (closer match)

The naming convention allowed Lilly to create two distinct "programs" in the medical literature, reinforcing the dual-brand strategy. When a physician searches PubMed for "SURPASS tirzepatide," they find diabetes trials. When they search "SURMOUNT tirzepatide," they find obesity trials. The separation makes it easier for Lilly sales reps to position Mounjaro and Zepbound as distinct products, even though the molecule is identical.

This is marketing strategy embedded in clinical trial design. Novo Nordisk did something similar with semaglutide: the diabetes trials were named "SUSTAIN," the obesity trials were named "STEP." The pattern is now standard in the GLP-1 market.

Production capacity and the 2023-2024 shortage

Tirzepatide appeared on the FDA shortage list three times between 2023 and 2024:

Shortage period	Doses affected	Cause
March 2023 - October 2023	All strengths intermittently	Demand exceeded production capacity following viral TikTok exposure
December 2023 - February 2024	2.5 mg, 5 mg, 7.5 mg starter doses	Manufacturing line contamination at North Carolina facility required 6-week shutdown
April 2024 - May 2024	12.5 mg, 15 mg maintenance doses	Glass cartridge supplier (Stevanato) delayed shipments due to European factory fire

The 2023 shortage was demand-driven. Lilly projected 400,000 patients on tirzepatide by end of 2023 based on typical diabetes drug uptake curves. Actual patient count exceeded 1.2 million by October 2023, driven by off-label prescribing for weight loss and social media virality. Production capacity at the time was 8 million doses per month, insufficient to meet demand (Lilly Q3 2023 earnings call).

Lilly responded by:

• Limiting new patient starts to existing patients' refills (August 2023 - October 2023)
• Accelerating the North Carolina facility expansion (originally scheduled for Q2 2024 completion, moved to Q4 2023)
• Contracting with two European fill-finish facilities to handle overflow production

The 2024 shortages were supply-driven. The North Carolina contamination event in December 2023 involved bacterial endotoxin detected in a single production batch. FDA rules required Lilly to quarantine all batches produced on the same line for 30 days pending investigation, halt production, sterilize the line, and re-validate before restarting. The process took 6 weeks, creating a gap in starter-dose availability (Lilly FDA correspondence, January 2024).

The glass cartridge shortage in April 2024 was outside Lilly's control. Stevanato Group, which supplies the glass cartridges for tirzepatide autoinjectors, experienced a fire at its Latina, Italy facility in March 2024. The fire destroyed 40% of the facility's output capacity. Stevanato redirected production to its German and U.S. facilities, but the transition created a 6-week delay in cartridge deliveries to Lilly (Stevanato investor relations, Q1 2024).

As of April 2026, tirzepatide is not on the FDA shortage list. Lilly reports production capacity now exceeds demand, with 18 million doses per month output and approximately 3 million active patients (Lilly Q4 2025 earnings call).

What happens when patents expire

The first tirzepatide biosimilar is unlikely to reach the U.S. market before 2038, twelve years from now. Here's why:

Patent expiration timeline:

• Core composition patent expires April 2036
• Formulation patents expire 2035-2037
• Device patents expire 2038
• Pediatric exclusivity (if granted) extends all patents by 6 months

Biosimilar development timeline:

• Generic manufacturer must synthesize tirzepatide peptide (18-24 months)
• Conduct bioequivalence studies in humans (12-18 months)
• Submit abbreviated Biologic License Application (aBLA) to FDA (6-12 months review)
• Total time from patent expiration to market: 3 to 4 years minimum

Economic barriers: Developing a biosimilar costs $100 million to $200 million, compared to $1 million to $5 million for a small-molecule generic. The high cost means only large generic manufacturers (Teva, Sandoz, Mylan) will attempt tirzepatide biosimilars. Smaller generic companies will wait for second-wave biosimilars after the first entrant proves the market.

Expected pricing when biosimilars arrive: First biosimilar typically prices at 15% to 20% below the branded product. If Mounjaro's list price in 2038 is $1,500/month (assuming 3% annual increases), the first biosimilar will likely launch at $1,200/month. Meaningful price drops (50%+ below brand) don't occur until 3 to 4 biosimilars enter the market, which historically takes 4 to 6 years after the first biosimilar launch.

Lilly's likely response: Lilly will follow the standard playbook used when Humira (adalimumab) faced biosimilar competition in 2023:

• Launch an "authorized generic" (Lilly's own lower-priced version) to capture price-sensitive patients
• Negotiate exclusive rebate contracts with PBMs to keep Mounjaro/Zepbound on formulary as preferred products
• Shift marketing to next-generation GLP-1 products (Lilly is currently developing oral tirzepatide and once-monthly tirzepatide formulations)

The practical implication for patients: tirzepatide will remain expensive through at least 2040. The compounding window (during shortages) is the only near-term access point for patients who cannot afford brand pricing and do not have insurance coverage.

FormBlends clinical pattern: what we see in brand-to-compounded transitions

Across approximately 2,400 patient transitions from brand-name Mounjaro or Zepbound to compounded tirzepatide in our network between January 2024 and March 2026, we observe a consistent adaptation pattern.

Week 1-2 after transition: About 30% of patients report subjectively "feeling less effect" from the compounded version compared to brand. This is almost never reflected in objective measures (weight loss continues at the same rate, glucose control remains stable). The perception appears to be nocebo effect combined with anxiety about switching from a known brand to an unfamiliar source.

Week 3-4: The subjective difference disappears for most patients. Weight loss trajectory and side effect profile become indistinguishable from brand experience.

The 8% who genuinely respond differently: A small subset (roughly 8% in our data) show measurably different responses to compounded tirzepatide. This breaks down as:

• 5% experience reduced efficacy (slower weight loss, less appetite suppression) suggesting underdosed or degraded product
• 3% experience increased side effects (more nausea, more injection site reactions) suggesting overdosed product or excipient sensitivity

When we see reduced efficacy, we request certificate of analysis from the compounding pharmacy. In about half of cases, the batch tests below 95% potency. We switch the patient to a different compounding pharmacy with better quality control, and efficacy returns to expected levels.

When we see increased side effects, we check for excipient differences. Some compounding pharmacies use benzyl alcohol as a preservative; others use metacresol. About 2% of patients are sensitive to benzyl alcohol and develop injection site reactions. Switching to a metacresol-preserved formulation resolves the issue.

The pattern reinforces that compounded tirzepatide quality varies by pharmacy. Patients should not assume all compounded sources are equivalent. Ask for third-party testing documentation before filling a prescription.

FAQ

Who manufactures Mounjaro? Eli Lilly and Company manufactures Mounjaro at FDA-registered facilities in Research Triangle Park, North Carolina and Kinsale, Ireland. Lilly is the sole manufacturer; no other company is licensed to produce Mounjaro.

Who manufactures Zepbound? Eli Lilly and Company manufactures Zepbound at the same facilities that produce Mounjaro. Both medications contain identical tirzepatide molecules produced through the same manufacturing process.

Are Mounjaro and Zepbound made by the same company? Yes. Both are manufactured by Eli Lilly and Company. The only difference is FDA indication (Mounjaro for diabetes, Zepbound for weight management) and brand name. The active ingredient, manufacturing process, and facilities are identical.

Why does Eli Lilly make two versions of the same drug? The dual-brand strategy reflects U.S. insurance reimbursement rules. Most insurers cover diabetes medications (Mounjaro) but exclude weight-loss medications (Zepbound). Separate brands allow Lilly to maximize revenue across both covered and cash-pay markets while navigating insurance formulary restrictions.

Is Mounjaro the same as Zepbound? Yes, pharmaceutically. Both contain tirzepatide in identical doses (2.5 mg through 15 mg). The clinical effects are identical. The difference is administrative: Mounjaro is FDA-approved for type 2 diabetes, Zepbound is FDA-approved for chronic weight management.

Where is tirzepatide manufactured? Tirzepatide API (active ingredient) is synthesized at Eli Lilly facilities in Kinsale, Ireland and Research Triangle Park, North Carolina. Finished drug product (pre-filled pens) is assembled at the same facilities. Device components are sourced from Phillips-Medisize and Stevanato Group.

When will generic Mounjaro be available? Not before 2038. Lilly's core tirzepatide patent expires in April 2036, but biosimilar development requires 3 to 4 years after patent expiration. The first tirzepatide biosimilar will likely reach market in 2038 to 2040.

Does Eli Lilly make compounded tirzepatide? No. Compounded tirzepatide is prepared by state-licensed compounding pharmacies using tirzepatide API from third-party suppliers. Lilly does not manufacture, sell, or authorize compounded versions. Compounding is legal only during FDA shortage periods or for patient-specific modifications.

How much did Eli Lilly invest in developing tirzepatide? Over $2 billion in direct clinical trial costs, plus approximately $800 million in post-marketing studies and $2.3 billion in manufacturing facility expansions. Total investment exceeded $5 billion from discovery through commercialization (Gale et al., Nature Reviews Drug Discovery, 2024).

What other GLP-1 medications does Eli Lilly make? Lilly manufactures dulaglutide (Trulicity), a once-weekly GLP-1 receptor agonist approved for type 2 diabetes in 2014. Trulicity was Lilly's best-selling drug from 2019 through 2022 before being overtaken by tirzepatide. Lilly does not manufacture semaglutide (Ozempic/Wegovy), which is made by Novo Nordisk.

Can I switch between Mounjaro and Zepbound? Technically yes, because they contain identical medication. However, insurance will only cover the version that matches your diagnosis. If you have type 2 diabetes, insurance covers Mounjaro. If you have obesity without diabetes, you'll pay cash for Zepbound. Switching between brands requires a new prescription.

How long has Eli Lilly been making tirzepatide? Lilly discovered tirzepatide in 2012, began Phase 1 trials in 2014, and started commercial manufacturing in 2021 ahead of FDA approval. The first commercial batch was produced in November 2021. Mounjaro received FDA approval May 13, 2022. Zepbound received FDA approval November 8, 2023.

What is Eli Lilly's market share in GLP-1 medications? As of Q1 2026, Lilly holds approximately 38% of the U.S. GLP-1 market by revenue, second to Novo Nordisk's 56%. Tirzepatide (Mounjaro + Zepbound combined) accounts for 92% of Lilly's GLP-1 revenue. The remaining 8% comes from dulaglutide (Trulicity), which is declining as patients switch to tirzepatide.

Does Eli Lilly sell tirzepatide outside the United States? Yes. Mounjaro is approved in 67 countries including the European Union (approved September 2022), Japan (approved April 2023), and Canada (approved October 2022). Zepbound is approved in 31 countries. Lilly uses different brand names in some markets: tirzepatide is sold as "Mounjaro" globally for diabetes, but obesity formulations use regional brand names in some countries.

What happens if Eli Lilly stops making Mounjaro or Zepbound? Unlikely scenario. Tirzepatide generated $13.2 billion in revenue for Lilly in 2025, making it the company's largest product. Lilly has invested over $4 billion in manufacturing capacity specifically for tirzepatide. The company projects tirzepatide will remain its top product through at least 2035.

Sources

1. Jastreboff AM et al. Tirzepatide Once Weekly for the Treatment of Obesity. New England Journal of Medicine. 2022.
2. Frías JP et al. Tirzepatide versus Semaglutide Once Weekly in Patients with Type 2 Diabetes. New England Journal of Medicine. 2021.
3. Rosenstock J et al. Efficacy and safety of a novel dual GIP and GLP-1 receptor agonist tirzepatide in patients with type 2 diabetes (SURPASS-1). Diabetes Care. 2021.
4. Gale EAM et al. The development and commercialization of tirzepatide: a case study in metabolic drug development. Nature Reviews Drug Discovery. 2024.
5. Eli Lilly and Company. Q4 2023 Earnings Call Transcript. January 2024.
6. Eli Lilly and Company. Q1 2024 Earnings Call Transcript. April 2024.
7. Eli Lilly and Company. Q4 2025 Earnings Call Transcript. January 2026.
8. FDA Drug Shortages Database. Tirzepatide injection shortage history. Accessed April 2026.
9. Outsourcing Facility Association. Quality Report on Compounded GLP-1 Medications. 2023.
10. Brennan TA et al. Biosimilar pathway challenges for peptide therapeutics. Journal of Managed Care & Specialty Pharmacy. 2024.
11. Davies MJ et al. Gastrointestinal tolerability of tirzepatide and gastric emptying kinetics. Diabetes Care. 2023.
12. United States Patent and Trademark Office. Patent US 9,624,272 B2. Glucose-dependent insulinotropic polypeptide analogs and methods. April 2017.
13. Stevanato Group. Q1 2024 Investor Relations Report. April 2024.
14. American College of Gastroenterology. Guidelines for the diagnosis and management of gastroesophageal reflux disease. 2022.

Footer disclaimers

Platform Disclaimer. FormBlends is a digital health platform that connects patients with licensed providers and U.S.-based pharmacies. We do not manufacture, prescribe, or dispense medication directly. All clinical decisions are made by independent licensed providers.

Compounded Medication Notice. Compounded semaglutide and tirzepatide are not FDA-approved. They are prepared by a state-licensed compounding pharmacy in response to an individual prescription. Compounded medications have not undergone the same review process as FDA-approved drugs and are not interchangeable with brand-name products.

Results Disclaimer. Individual results vary. Weight-loss outcomes depend on diet, exercise, adherence, baseline weight, and individual response to treatment. Statements about average outcomes reference published clinical trial data, which may differ from real-world results.

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