Tirzepatide vs Semaglutide: What’s the Difference?
Semaglutide and tirzepatide are the two best-known once-weekly incretin peptides. Both are lipidated so they bind albumin and last for days, but they come from different companies, different starting hormones and a different number of receptors.
Semaglutide (Novo Nordisk) is a 31-residue analogue of human GLP-1 and a selective GLP-1 receptor agonist. It is the active ingredient of Ozempic, Wegovy and Rybelsus.
Tirzepatide (Eli Lilly, LY3298176) is a 39-residue peptide built on the GIP sequence that activates two receptors: GIP and GLP-1. It is the active ingredient of Mounjaro and Zepbound.
In short: semaglutide is a one-receptor molecule and tirzepatide a two-receptor one. Unlike most pairs on this site, these two have been compared head to head, in two Lilly-sponsored trials.
Tirzepatide vs Semaglutide at a Glance
Tirzepatide is a 39-residue GIP-backbone peptide (C225H348N48O68, 4,813.53 g/mol) that activates two receptors. Semaglutide is a 31-residue GLP-1 analogue (C187H291N45O59, 4,113.58 g/mol) that activates one. Both are FDA-approved.
| Comparison | Tirzepatide | Semaglutide |
|---|---|---|
| Peptide length | 39 amino acids | 31 amino acids |
| Molecular weight | 4,813.53 g/mol | 4,113.58 g/mol |
| Sequence | YXEGTFTSDYSIXLDKIAQKAFVQWLIAGGPSSGAPPPS-NH2 | HXEGTFTSDVSSYLEGQAAKEFIAWLVRGRG |
| Molecular relationship | GIP-backbone dual agonist | GLP-1(7-37) analogue |
| Receptor activity | GIP and GLP-1 receptor signalling | Selective GLP-1 receptor signalling |
| Research evidence | Large phase 3 and outcomes trials; FDA-approved | Large phase 3 and outcomes trials; FDA-approved |
| FDA-approved drug | Yes (Mounjaro, Zepbound) | Yes (Ozempic, Wegovy, Rybelsus) |
What are Tirzepatide and Semaglutide
39 AA
Tirzepatide
A 39-residue lipidated peptide from Eli Lilly that activates the GIP and GLP-1 receptors, with more engagement of the GIP receptor at clinical exposures.
Research areas
GIPR • GLP-1R • Incretin biology • Metabolic models
X = Aib at positions 2 and 13; Lys20 carries a C20 fatty diacid through γGlu and two AEEA linkers. Lilly's pharmacology work calls it imbalanced (more GIPR than GLP-1R engagement) and biased toward cAMP at GLP-1R. The FDA label gives a half-life of about 5 days.
Explore GLP-2 Tirz (tirzepatide)31 AA
Semaglutide
A 31-residue GLP-1 analogue from Novo Nordisk with 94% sequence homology to human GLP-1, acting on the GLP-1 receptor only.
Research areas
GLP-1R • Incretin biology • Metabolic and cardiovascular outcomes research
X = Aib at position 8, which protects against DPP-4; Arg34 replaces Lys; Lys26 carries a C18 fatty diacid through a hydrophilic spacer. The FDA label gives an elimination half-life of about one week.
Semaglutide: GLP-1(7-37) analogueGLP-1R only vs GIPR + GLP-1RTirzepatide: GIP-based dual agonist
Different starting hormone, one receptor apart
Key Differences Between Tirzepatide and Semaglutide
| Key differences | Tirzepatide | Semaglutide |
|---|---|---|
| Receptors | Two: GIP receptor and GLP-1 receptor. |
One: the GLP-1 receptor (the label calls it selective). |
| Backbone | Built on the GIP sequence; 39 residues with a C-terminal amide. |
Built on human GLP-1(7-37); 31 residues with a free C-terminal acid. |
| Lipidation | C20 fatty diacid on Lys20 via γGlu and two AEEA units. |
C18 fatty diacid on Lys26 (GLP-1 numbering) via two AEEA units and γGlu. |
| Reported half-life | About 5 days (FDA label). |
About 1 week (FDA label). |
| Developer and brands | Eli Lilly: Mounjaro (2022) and Zepbound (2023). |
Novo Nordisk: Ozempic (2017), Rybelsus (2019) and Wegovy (2021). |
| Head-to-head trials | SURPASS-2 in type 2 diabetes (40 weeks) and SURMOUNT-5 in obesity (72 weeks), both Lilly-sponsored. |
The comparator arm in both trials. |
How their research profiles differ
- Tirzepatide
- 39-AA GIP-backbone peptide
- GIP + GLP-1 receptors
- Dual-agonist incretin research
- Semaglutide
- 31-AA GLP-1 analogue
- GLP-1 receptor only
- Selective GLP-1 research
Tirzepatide vs Semaglutide: Which Is Better?
For these two there is direct evidence. SURPASS-2 (1,879 adults with type 2 diabetes, 40 weeks) and SURMOUNT-5 (751 adults with obesity, 72 weeks) compared them head to head, with change in HbA1c and percentage change in body weight as their primary end points. Tirzepatide met the primary end point of both, superiority over semaglutide on that measure (Frías et al., NEJM 2021; Aronne et al., NEJM 2025). The full results are in the two papers listed under References.
Both trials were sponsored by Eli Lilly, tirzepatide's developer, and SURMOUNT-5 was open-label. Semaglutide has the longer record, including completed cardiovascular, kidney and MASH outcome trials.
For laboratory work the useful distinction is pharmacological: semaglutide isolates GLP-1 receptor signalling, while tirzepatide adds GIP receptor activity.
Does the model need selective GLP-1 receptor agonism, or combined GIP and GLP-1 receptor agonism?
Can Tirzepatide and Semaglutide Be Studied Together?
They can be compared as separate groups in one programme, which is what SURPASS-2 and SURMOUNT-5 did. Adding retatrutide as a third arm extends the series to the glucagon receptor.
Giving both in the same condition is a different question: both act on the GLP-1 receptor, so their effects would overlap.
There Isn’t One Universal “Winner”
Tirzepatide
Dual-agonist research profile
GIP • GLP-1 • FDA-approved molecule
Semaglutide
Selective GLP-1 research profile
GLP-1R only • FDA-approved molecule
Compare the Research. Verify the Material.
Clean Peptide stocks tirzepatide as GLP-2 Tirz. Each size ships against the certificate for its own lot, from HYTE Research Division (20 mg) or Accurate Test Labs (30 mg), with lot number, HPLC purity and identity on the product page.
We do not stock semaglutide at the moment. Retatrutide (GLP-3 Reta) and survodutide are in the catalogue with their own certificates.
Question
Frequently Asked
What is the difference between semaglutide and tirzepatide?
Semaglutide activates one receptor, the GLP-1 receptor. Tirzepatide activates two, the GIP and GLP-1 receptors. Semaglutide is a 31-residue GLP-1 analogue from Novo Nordisk; tirzepatide is a 39-residue GIP-based peptide from Eli Lilly.
Has tirzepatide been compared directly with semaglutide?
Yes, in two Lilly-sponsored phase 3 trials: SURPASS-2 in type 2 diabetes (primary end point HbA1c) and SURMOUNT-5 in obesity (primary end point percentage body-weight change), both published in NEJM. Tirzepatide met the primary end point, superiority over semaglutide, in both.
What is Mounjaro vs Ozempic?
Mounjaro is a brand of tirzepatide (Eli Lilly) and Ozempic a brand of semaglutide (Novo Nordisk). Zepbound and Wegovy are the same two molecules under their obesity-indication brands.
How long are their half-lives?
Tirzepatide's half-life is about 5 days and semaglutide's about one week, both per their FDA labels. Both are given once weekly as injections; semaglutide also has a daily oral tablet form.
Are both FDA-approved?
Yes. Semaglutide was first approved as Ozempic in December 2017; tirzepatide as Mounjaro in May 2022.
Where does retatrutide fit?
Retatrutide, also from Eli Lilly, activates three receptors: GIP, GLP-1 and glucagon. It is investigational and not approved anywhere.
Does Clean Peptide sell semaglutide?
Not at the moment. We stock tirzepatide (GLP-2 Tirz), retatrutide (GLP-3 Reta) and survodutide, each with per-lot certificates.
Research Peptides. Documented by Batch.
Every size in the catalogue ships against the certificate issued for its own lot.
For laboratory research use only. Not for human or veterinary use.
References
Identity data come from the FDA labels, the FDA substance registry (GSRS), KEGG and PubChem. Trial descriptions follow the PubMed abstracts.
- Lau J, et al. Discovery of the Once-Weekly Glucagon-Like Peptide-1 (GLP-1) Analogue Semaglutide Journal of Medicinal Chemistry, 2015. Design, substitutions and albumin binding.
- Coskun T, et al. 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 Molecular Metabolism, 2018. Discovery of tirzepatide.
- Willard FS, et al. Tirzepatide is an imbalanced and biased dual GIP and GLP-1 receptor agonist JCI Insight, 2020. Receptor pharmacology.
- Frías JP, et al. Tirzepatide versus Semaglutide Once Weekly in Patients with Type 2 Diabetes NEJM, 2021. SURPASS-2.
- Aronne LJ, et al. Tirzepatide as Compared with Semaglutide for the Treatment of Obesity NEJM, 2025. SURMOUNT-5.
- Marso SP, et al. Semaglutide and Cardiovascular Outcomes in Patients with Type 2 Diabetes NEJM, 2016. SUSTAIN 6.
- FDA label Ozempic (semaglutide) injection Structure, formula, molecular weight, selectivity and half-life.
- FDA label Mounjaro (tirzepatide) injection Structure, formula, molecular weight and half-life.
