Active substance · GLP-1 + GIP dual agonist
Tirzepatide
The active substance in Mounjaro and Zepbound. A dual-receptor agonist that combines GLP-1 and GIP and can achieve up to 22% weight loss — the highest effectiveness of any approved weight-loss medication.
Active substance
Tirzepatide
Class
GLP-1 + GIP
Brands
Mounjaro / Zepbound
Weight loss
Up to 22.5%
What is tirzepatide?
Tirzepatide is a synthetic peptide medicine from Eli Lilly, on the European market since 2022 under the brand name Mounjaro. It is the first and currently the only approved dual-receptor agonist: it activates both the GLP-1 receptor and the GIP receptor. This dual action makes tirzepatide on average more effective for weight loss than single-receptor agonists such as semaglutide.
In the Netherlands, tirzepatide (Mounjaro) has been reimbursed under basic health insurance for type 2 diabetes after metformin since 2024. For obesity it has also been EMA-approved since 2024, but reimbursement is limited to specific groups under the GVS criteria. Zepbound, the US brand name, is not available in the Netherlands but contains exactly the same active substance.
For the individual brands, see our pages on Mounjaro (European version) and Zepbound (US version, identical). You will find an in-depth comparison with semaglutide in Mounjaro vs Ozempic.
The dual-receptor mechanism
Tirzepatide acts on two different incretin hormone receptors, which complement each other in their metabolic effect.
Glucagon-like peptide-1
GLP-1
Slows gastric emptying, increases satiety, stimulates glucose-dependent insulin release. Responsible for most of the satiety effect and blood sugar effect.
Glucose-dependent insulinotropic polypeptide
GIP
Enhances insulin release from the pancreas, especially after meals. GIP activation also influences the central satiety centre and contributes to long-term weight loss through lipolysis in fat tissue.
The combination of both activations produces a synergistic effect: not 1+1=2, but closer to 1+1=2.5 where weight loss is concerned. This explains why tirzepatide works more strongly than semaglutide at a comparable dose level.
Clinical evidence SURMOUNT & SURPASS
Tirzepatide has been extensively studied through two trial programmes: SURPASS (type 2 diabetes) and SURMOUNT (obesity management).
| Trial | Population | Result | Publication |
|---|---|---|---|
| SURMOUNT-1 | Obesity without diabetes | 22.5% weight loss (15 mg, 72 wks) | NEJM 2022 |
| SURMOUNT-2 | Obesity with type 2 diabetes | 15.7% weight loss | Lancet 2023 |
| SURPASS-1 | Type 2 diabetes, monotherapy | HbA1c -2.1%, weight loss 7-10 kg | Lancet 2021 |
| SURPASS-3 | Diabetes + metformin | HbA1c -2.5%, 12 kg weight loss | Lancet 2021 |
| SURPASS-4 | Diabetes + cardiovascular risk | -2.4% HbA1c, cardiac safety confirmed | Lancet 2021 |
Tirzepatide at Go Leaner
Our BIG-registered doctors prescribe tirzepatide (Mounjaro) when maximum weight loss is the priority and the patient meets the indication. Including blood tests, a personal titration schedule and monthly check-ups.
Read more about tirzepatide medications
In-depth, medically reviewed articles — written by our physicians.
Medication overview
Compare all GLP-1 and obesity medication
Our BIG-registered doctors only prescribe medication after a thorough intake. The overviews below explain how each one works, dosing and risks.
Prescription in NL
Ozempic
Weekly semaglutide injection
View OzempicPrescription in NL
Wegovy
Semaglutide 2.4 mg for obesity
View WegovyPrescription in NL
Mounjaro
Tirzepatide — GLP-1 + GIP
View MounjaroPrescription in NL
Saxenda
Daily liraglutide injection
View SaxendaPrescription in NL
Rybelsus
Oral semaglutide tablet
View RybelsusPrescription in NL
Mysimba
Naltrexone/bupropion combination
View MysimbaPrescription in NL
Semaglutide
Active ingredient in Ozempic, Wegovy and Rybelsus
View SemaglutideUS only
Zepbound
US brand name for tirzepatide
View Zepbound