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Ozempic vs Mounjaro: Semaglutide vs Tirzepatide for Weight Loss
Discover the key differences between Ozempic and Mounjaro, including semaglutide vs tirzepatide, weight-loss evidence, how they work, side effects and important UK prescribing information.
Ozempic vs Mounjaro is one of the most searched comparisons for people researching GLP-1 medicines and weight management. But are they actually the same type of treatment? What is the difference between semaglutide and tirzepatide, and which has shown greater weight loss in clinical research?
Medical information:
This article is for educational purposes only and is not a
substitute for advice from a qualified healthcare professional.
Ozempic and Mounjaro are prescription medicines and should only
be used following an appropriate clinical assessment and
prescription.
Ozempic vs Mounjaro: Quick Comparison
Ozempic and Mounjaro are prescription medicines used in metabolic health, but they contain different active ingredients and work through different hormone pathways.
| Feature | Ozempic | Mounjaro |
|---|---|---|
| Active ingredient | Semaglutide | Tirzepatide |
| Main mechanism | GLP-1 receptor agonist | GIP and GLP-1 receptor agonist |
| Medicine type | GLP-1 receptor agonist | Dual GIP/GLP-1 receptor agonist |
| UK diabetes indication | Yes | Yes |
| UK weight-management indication | Not Ozempic | Yes, under licensed criteria |
| Weight-management semaglutide brand | Wegovy | Mounjaro |
| Administration | Once weekly injection | Once weekly injection |
| Common side effects | Mainly gastrointestinal | Mainly gastrointestinal |
What Is Ozempic?
Ozempic is a prescription medicine containing semaglutide.
Semaglutide belongs to the GLP-1 receptor agonist class. GLP-1 is a naturally occurring hormone involved in appetite, digestion and blood glucose regulation.
Ozempic is licensed in the UK for the treatment of adults with type 2 diabetes alongside appropriate diet and exercise measures.
Important UK distinction:
Ozempic and Wegovy both contain semaglutide, but they have
different licensed uses. Wegovy is the semaglutide brand
specifically licensed for weight management under specified
conditions.
What Is Semaglutide?
Semaglutide is the active ingredient found in medicines including Ozempic and Wegovy.
Clinical research has demonstrated substantial weight reduction with once-weekly semaglutide 2.4 mg when combined with lifestyle intervention.
What Is Mounjaro?
Mounjaro contains tirzepatide, a medicine that acts on two hormone pathways: GIP and GLP-1.
Tirzepatide is therefore often described as a dual GIP/GLP-1 receptor agonist.
Unlike Ozempic, Mounjaro has a UK licence covering both type 2 diabetes and weight management, subject to the applicable prescribing criteria.
Semaglutide vs Tirzepatide: What Is the Difference?
The biggest difference between semaglutide and tirzepatide is how they act on the body’s hormone pathways.
Semaglutide
Semaglutide primarily activates the GLP-1 receptor.
- Appetite regulation
- Feelings of fullness
- Food intake
- Blood glucose regulation
- Gastrointestinal processes
Tirzepatide
Tirzepatide activates both GIP and GLP-1 receptors.
This dual mechanism is one reason researchers have investigated whether tirzepatide can produce greater average weight reduction than GLP-1-only medicines.
Ozempic vs Mounjaro for Weight Loss
For people researching Ozempic vs Mounjaro for weight loss, it is important to compare the active ingredients and licensed indications rather than treating the brand names as interchangeable.
In the UK, Ozempic is licensed for type 2 diabetes, while Mounjaro also has a licensed indication for weight management subject to eligibility criteria.
Semaglutide’s weight-management brand is Wegovy.
Semaglutide vs Tirzepatide Weight Loss: What Does Research Show?
One of the most important pieces of evidence is the SURMOUNT-5 trial, which directly compared tirzepatide with semaglutide in adults with obesity who did not have type 2 diabetes.
After 72 weeks, the study reported greater average weight reduction with tirzepatide.
20.2%
Average weight reduction with tirzepatide
13.7%
Average weight reduction with semaglutide
The study found that tirzepatide produced a significantly greater reduction in body weight and waist circumference than semaglutide.
Important:
These are average results from a clinical trial. They cannot
predict exactly how an individual person will respond to
either medicine.
How Do Semaglutide and Tirzepatide Work?
How Semaglutide Works
Semaglutide activates GLP-1 receptors. GLP-1 signalling can influence appetite, feelings of fullness and blood glucose regulation.
How Tirzepatide Works
Tirzepatide activates both GIP and GLP-1 receptors. This combined activity affects appetite and metabolic processes.
Individual responses can vary considerably.
Ozempic vs Mounjaro: Which Causes More Weight Loss?
Based on the direct 72-week SURMOUNT-5 comparison, tirzepatide produced greater average weight loss than semaglutide in the studied population.
| Medicine | Active Ingredient | Average Weight Reduction | Study Duration |
|---|---|---|---|
| Mounjaro | Tirzepatide | 20.2% | 72 weeks |
| Semaglutide | Semaglutide | 13.7% | 72 weeks |
However, this does not mean Mounjaro is automatically the right treatment for every person.
Ozempic vs Mounjaro Side Effects
Both medicines can cause gastrointestinal side effects.
- Nausea
- Vomiting
- Diarrhoea
- Constipation
- Abdominal discomfort
- Reduced appetite
Side effects can vary between individuals. Anyone considering treatment should discuss the full safety profile, contraindications, interactions and monitoring requirements with an appropriately qualified healthcare professional.
Ozempic vs Mounjaro: Which Is Better?
There is no universal answer to “Is Ozempic or Mounjaro better?”
If the question is specifically about average weight reduction in the population studied in SURMOUNT-5, tirzepatide produced greater average weight loss than semaglutide.
However, choosing a prescription medicine involves much more than comparing two percentages.
- Medical history
- Current medicines
- BMI and weight-related health conditions
- Diabetes status
- Potential contraindications
- Previous treatment response
- Side-effect profile
- Individual treatment goals
Ozempic vs Mounjaro in the UK
UK readers should pay particular attention to the difference between brand name, active ingredient and licensed indication.
| Brand | Active Ingredient | UK Licensed Use |
|---|---|---|
| Ozempic | Semaglutide | Type 2 diabetes |
| Wegovy | Semaglutide | Weight management under specified criteria |
| Mounjaro | Tirzepatide | Type 2 diabetes and weight management under specified criteria |
GLP-1 medicines are prescription-only medicines in the UK. They should be obtained through legitimate healthcare channels following appropriate clinical assessment.
Semaglutide and Tirzepatide With Diet and Exercise
Neither medicine should be viewed as a replacement for healthy lifestyle measures.
A sustainable weight-management approach may include:
- A balanced, nutrient-rich diet
- Adequate protein and fibre
- Regular physical activity
- Resistance training where appropriate
- Good sleep habits
- Behavioural support
- Regular clinical monitoring
Frequently Asked Questions
Is Ozempic the same as Mounjaro?
No. Ozempic contains semaglutide, while Mounjaro contains
tirzepatide. Semaglutide primarily acts through the GLP-1
receptor, whereas tirzepatide acts through both GIP and
GLP-1 receptors.
Is semaglutide or tirzepatide better for weight loss?
A 2025 head-to-head trial found greater average weight
reduction with tirzepatide than semaglutide after 72 weeks
in adults with obesity without type 2 diabetes. Individual
responses vary.
Is Ozempic approved for weight loss in the UK?
Ozempic is licensed in the UK for type 2 diabetes.
Semaglutide’s UK weight-management brand is Wegovy,
which has a specific weight-management indication under
applicable criteria.
Is Mounjaro approved for weight management in the UK?
Yes. Mounjaro (tirzepatide) has a UK licence for weight
management in eligible adults, subject to the applicable
criteria.
Is Mounjaro a GLP-1 medicine?
Mounjaro contains tirzepatide, which acts on both GIP and
GLP-1 receptors. It is therefore more accurately described
as a dual GIP/GLP-1 receptor agonist.
Can semaglutide and tirzepatide be taken together?
They should not be combined unless specifically directed
by an appropriately qualified healthcare professional.
These are prescription medicines requiring individual
clinical assessment.
How long does it take to lose weight with semaglutide or tirzepatide?
Weight loss varies between individuals and generally
develops over time. Clinical studies measure outcomes
over many months, with treatment typically involving
gradual dose escalation and ongoing monitoring.
Are Ozempic and Mounjaro prescription-only medicines?
Yes. They are prescription medicines in the UK and should
be used under appropriate healthcare-professional
supervision.
Key Takeaways
Ozempic vs Mounjaro is ultimately a comparison between two different active ingredients: semaglutide and tirzepatide.
Semaglutide primarily targets the GLP-1 receptor, while tirzepatide targets both GIP and GLP-1 receptors.
Clinical evidence has demonstrated substantial weight loss with both medicines. In the 2025 SURMOUNT-5 head-to-head trial, tirzepatide produced greater average weight reduction than semaglutide after 72 weeks.
However, the best treatment cannot be determined by weight loss percentages alone. Eligibility, medical history, potential side effects, contraindications and individual treatment goals all matter.
If you are considering prescription weight-management treatment, speak with a qualified healthcare professional who can assess whether treatment is appropriate for you.
Sources & Further Reading
- UK Medicines and Healthcare products Regulatory Agency (MHRA)
- National Institute for Health and Care Excellence (NICE)
- New England Journal of Medicine — SURMOUNT-5
- New England Journal of Medicine — STEP 1
- New England Journal of Medicine — SURMOUNT-1