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| GLP-1 | Mounjaro | |
|---|---|---|
| What it is | A hormone the intestine releases after eating, and the name of the drug class that mimics it12 | A brand-name weekly injection of tirzepatide, which activates the GIP and GLP-1 receptors3 |
| Active ingredient | In the drugs on FDA's 2024 list: exenatide, liraglutide, dulaglutide, lixisenatide, semaglutide and tirzepatide2 | Tirzepatide3 |
| Maker | The body makes GLP-1; the drugs come from several companies, such as Novo Nordisk (Ozempic) and Eli Lilly (Trulicity)514 | Eli Lilly and Company4 |
| Form | Injections taken twice daily (Byetta), once daily (Victoza) or once weekly (Ozempic, Trulicity), plus daily tablets such as Rybelsus875146 | Injection only: single-dose pens and vials, multi-dose vials and KwikPens3 |
| Approved uses | On FDA's 2024 list: type 2 diabetes for most products; weight management for Saxenda, Wegovy and Zepbound2 | Blood sugar control in type 2 diabetes (adults and children 10 and older) and lower major cardiovascular event risk in high-risk adults with type 2 diabetes3 |
| Dosing schedule | Ranges from 5 mcg twice daily (Byetta, to start) to once weekly (Ozempic, 0.25 to 2 mg), set per label85 | Starts at 2.5 mg a week and rises by 2.5 mg no sooner than every 4 weeks, to 15 mg at most (10 mg for children)3 |
| First US approval | 2005, when FDA approved the first GLP-1 receptor agonist, Byetta (exenatide)2 | May 13, 20224 |
Key differences
Is Mounjaro a GLP-1?
The question mixes two meanings of "GLP-1". One is the natural hormone. The intestine releases it, it helps lower blood sugar after eating, and it acts in brain areas that control appetite and food intake.1 The other is the drug class, GLP-1 receptor agonists, which mimic that hormone.2 FDA's 2024 list of approved GLP-1 receptor agonists runs from Byetta in 2005 to Mounjaro in 2022 and Zepbound in 2023.2
Mounjaro is on that list, but its mechanism differs from the drugs before it. Its label calls tirzepatide a GIP receptor and GLP-1 receptor agonist: besides the GLP-1 receptor, it activates the receptor for GIP (glucose-dependent insulinotropic polypeptide), a second hormone.3 Semaglutide's label, by contrast, says it selectively binds to and activates the GLP-1 receptor.5 FDA's pharmacologic class description of tirzepatide, shown in PubChem, carries both receptor names.10 MedlinePlus places tirzepatide in the class called incretin mimetics.11
What the second receptor adds
Lab work shows how the two targets are balanced. In cell studies, tirzepatide bound the GIP receptor about as strongly as natural GIP. It bound the GLP-1 receptor about 5 times more weakly than natural GLP-1, and it had minimal activity at the related glucagon receptor.12 A 2020 laboratory study found that, at clinical doses, tirzepatide engages the GIP receptor more than the GLP-1 receptor, and its authors called the drug "imbalanced".13 These are cell and modeling results, not trial outcomes.
In people, the label describes the combined effect. Tirzepatide raises insulin release and lowers glucagon, both in a glucose-dependent way, and it delays stomach emptying.3 The delay is largest after the first dose and fades over time.3 After 28 weeks, 15 mg lowered fasting glucagon by 28% and after-meal glucagon by 43%, with no change on placebo.3 FDA describes GLP-1 receptor agonists as a class in similar terms: they stimulate insulin release, reduce blood sugar after a meal, and slow food moving through the digestive tract, which can help a person feel full longer.2
What Mounjaro shares with the GLP-1 class
The safety picture is close to the rest of the class. In rodent studies, semaglutide, tirzepatide, liraglutide, dulaglutide and extended-release exenatide all caused thyroid C-cell tumors.537149 Whether they cause these tumors in humans is unknown.53 Their labels carry a boxed warning, and Mounjaro must not be used by people with a personal or family history of medullary thyroid carcinoma or with MEN 2.3
Stomach and gut effects are the most common side effects across the class, and each label raises the dose in steps to reduce them.53 On Mounjaro, nausea affected 12%, 15% and 18% of people on 5, 10 and 15 mg, vs 4% on placebo, mostly while the dose was being raised.3 Several Mounjaro warnings, including pancreatitis, kidney injury and food entering the lungs during anesthesia, cite reports with GLP-1 receptor agonists as a class.3 Its label also warns that birth control pills may work less well for 4 weeks after starting and after each dose increase, and advises a non-oral or added barrier method in those weeks.3
Trials against GLP-1-only drugs
Two trials compared tirzepatide directly with GLP-1-only drugs. In SURPASS-2, 1,879 adults with type 2 diabetes on metformin took tirzepatide or semaglutide 1 mg weekly for 40 weeks. HbA1c fell 2.0, 2.2 and 2.3 percentage points on 5, 10 and 15 mg vs 1.9 on semaglutide; the label's table marks all three doses as statistically superior, although its text names only 10 and 15 mg. Weight fell 7.6, 9.3 and 11.2 kg vs 5.7 kg.3 Semaglutide was tested at 1 mg, below the 2 mg maximum on Ozempic's current label.5 In SURPASS-CVOT, the comparator was dulaglutide 1.5 mg weekly, the active ingredient of Trulicity.314 Mounjaro was non-inferior for heart attack, stroke and cardiovascular death, but it was not shown to be superior.3
Where Mounjaro sits in time
GLP-1 drugs have a 17-year head start. Byetta (exenatide) came first in 2005, followed by Victoza (liraglutide) in 2010, Trulicity (dulaglutide) in 2014, Ozempic (semaglutide) in 2017 and Rybelsus in 2019.2 Mounjaro arrived on May 13, 2022, as a new molecular entity.42 The older drugs differ in schedule too. Byetta starts at 5 mcg twice daily and Victoza at 0.6 mg once daily, while Mounjaro and Trulicity are given once a week.87143 For each of these drugs, the prescriber sets the dose and each step up within the label's schedule.314
Which page to read next
Start with What is GLP-1? for the hormone and the whole drug class, then GLP-1 side effects and GLP-1 benefits and uses. For the brand itself, read What is Mounjaro? and Mounjaro and blood sugar; the tirzepatide profile covers the compound. Related pairs: GLP-1 vs semaglutide and Mounjaro vs tirzepatide. All pairs are on the GLP-1 comparisons page.
Frequently asked questions
Is Mounjaro a GLP-1 medication?
Yes, with a second target. FDA's 2024 list of approved GLP-1 receptor agonists includes Mounjaro, and notes that tirzepatide is a dual GIP receptor and GLP-1 receptor agonist.2 Its label calls tirzepatide a GIP receptor and GLP-1 receptor agonist, so it activates two hormone receptors.3 Semaglutide, by contrast, selectively binds to and activates the GLP-1 receptor.5 So Mounjaro is grouped with the GLP-1 drugs, but it is not a GLP-1-only drug.
Does tirzepatide activate the GIP receptor?
Yes. In cell studies published in 2018, tirzepatide bound the GIP receptor about as strongly as natural GIP, and the GLP-1 receptor about 5 times more weakly than natural GLP-1. It had minimal activity at the related glucagon receptor.12 A 2020 laboratory analysis found more engagement of the GIP receptor than the GLP-1 receptor at clinical doses.13 Both are lab findings, not results measured in people.
What class of medication does tirzepatide belong to?
PubChem lists two FDA pharmacologic classes for tirzepatide: Glucose-dependent Insulinotropic Polypeptide Receptor Agonist and GLP-1 Receptor Agonist.10 MedlinePlus places it in the class called incretin mimetics, and says it helps the pancreas release the right amount of insulin when blood sugar is high.11 In the US it is a prescription medicine, sold as Mounjaro for type 2 diabetes and as Zepbound for weight management.432
How does Mounjaro work?
Per its label, tirzepatide raises insulin release and lowers glucagon, both in a glucose-dependent way, and it delays stomach emptying. The delay is largest after the first dose and fades over time.3 After 28 weeks on 15 mg, fasting glucagon fell 28% and after-meal glucagon fell 43%, with no change on placebo.3 Mounjaro's uses are blood sugar control in type 2 diabetes and lowering major cardiovascular event risk in high-risk adults.3
Does Mounjaro lower blood sugar more than GLP-1-only drugs?
In one head-to-head trial, yes. In SURPASS-2, 1,879 adults with type 2 diabetes on metformin took tirzepatide or semaglutide 1 mg for 40 weeks. HbA1c fell 2.0, 2.2 and 2.3 percentage points on 5, 10 and 15 mg vs 1.9 on semaglutide, and the label's table marks all three doses as statistically superior.3 The trial used semaglutide 1 mg; Ozempic's label now goes up to 2 mg.5 Against dulaglutide in the SURPASS-CVOT heart trial, Mounjaro was non-inferior for major cardiovascular events, not superior.3
Do GLP-1 drugs and Mounjaro have the same side effects?
The patterns are similar. Stomach and gut effects are the most common across the class, and each label raises the dose in steps to reduce them.53 On Mounjaro, nausea affected 12% to 18% of people on 5 to 15 mg vs 4% on placebo.3 The labels share a boxed warning about thyroid C-cell tumors seen in rodents, plus warnings on pancreatitis, gallbladder disease and low blood sugar when combined with insulin or a sulfonylurea.53
Written by D2C Peptides Editorial Team.
Pending qualified review.
Updated .
Sources
- FDA Requests Removal of Suicidal Behavior and Ideation Warning from Glucagon-Like Peptide-1 Receptor Agonist (GLP-1 RA) Medications (Drug Safety Communication, 01-13-2026). U.S. Food and Drug Administration, 2026.
- Update on FDA's ongoing evaluation of reports of suicidal thoughts or actions in patients taking a certain type of medicines approved for type 2 diabetes and obesity (Drug Safety Communication, 01-11-2024). U.S. Food and Drug Administration, 2024.
- MOUNJARO (tirzepatide) injection Prescribing Information, Medication Guide and Instructions for Use, revised 08/2026 (NDA 215866/S-044, S-045). U.S. Food and Drug Administration (Drugs@FDA), 2026.
- Drugs@FDA: NDA 215866, Mounjaro (tirzepatide) application overview. U.S. Food and Drug Administration, 2026.
- OZEMPIC (semaglutide) injection, prescribing information (revised 5/2026). U.S. National Library of Medicine, DailyMed (label by Novo Nordisk), 2026.
- RYBELSUS and OZEMPIC (semaglutide) tablets, prescribing information (revised 1/2026). U.S. National Library of Medicine, DailyMed (label by Novo Nordisk), 2026.
- VICTOZA (liraglutide) injection, prescribing information (revised 10/2025). U.S. National Library of Medicine, DailyMed (label by Novo Nordisk), 2025.
- BYETTA (exenatide) injection, prescribing information (revised 9/2025). U.S. National Library of Medicine, DailyMed (label by AstraZeneca), 2025.
- BYDUREON BCISE (exenatide extended-release) injectable suspension, prescribing information (revised 5/2025). U.S. National Library of Medicine, DailyMed (label by AstraZeneca), 2025.
- Tirzepatide, CID 156588324: Names and Identifiers (FDA Pharm Classes description). PubChem, NIH National Library of Medicine, 2026.
- Tirzepatide Injection (drug information, revised 02/15/2026): drug class. MedlinePlus, NIH National Library of Medicine, 2026.
- LY3298176, a novel dual GIP and GLP-1 receptor agonist for the treatment of type 2 diabetes mellitus: From discovery to clinical proof of concept (Coskun et al.). Molecular Metabolism, 2018.
- Tirzepatide is an imbalanced and biased dual GIP and GLP-1 receptor agonist (Willard et al.), PubMed record PMID 32730231. JCI Insight (via NLM PubMed E-utilities), 2020.
- TRULICITY (dulaglutide) injection, prescribing information (revised 3/2026). U.S. National Library of Medicine, DailyMed (label by Eli Lilly), 2026.