The use of GLP-1 medications has increased in recent years, helping people with obesity and related health conditions lose weight.
Among the most widespread options are Mounjaro and Ozempic. When people are thinking about using weight-loss medications, they often compare Mounjaro vs Ozempic. But while they share a number of similarities, they aren’t the same.
Here, we’ll explore how effective they can be for weight loss, the potential side effects people might experience and how much they cost in the UK, to help people who might be looking at their options.
What are Mounjaro and Ozempic?
Mounjaro and Ozempic are injectable medications that were first developed to help treat type 2 diabetes but are now used by some people to help them support weight management.
Both medications are GLP-1 receptor agonists. This means they mimic the hormone GLP-1, which is produced in the gut and sends messages to the brain telling it that the stomach is full, helping reduce appetite and slow the emptying of the stomach. As a result, people taking these medications often eat less, consuming fewer calories and lose weight as a result.
Ozempic contains the active ingredient semaglutide, whereas Mounjaro contains the active ingredient tirzepatide. Whereas semaglutide is a GLP-1 receptor agonist, tirzepatide is both a GLP-1 and a GIP receptor agonist. GIP is another hormone, and it works alongside GLP-1 by changing how some of the fat in the body is stored.
So, while both can be effective in helping people lose weight, they work in slightly different ways, so people might see different weight loss results.
Comparing weight loss results on GLP-1s
Everyone’s body is different, but scientific studies have indicated that Mounjaro is generally more effective than Ozempic, particularly at higher doses. This is likely in part due to its dual-action mechanism.
A study published in 2025 found that tirzepatide was more effective than semaglutide in people with obesity who didn’t also have type 2 diabetes. Over 750 people were asked to take the maximum amount of either medication they could tolerate for a year and a half.
Those who took tirzepatide lost an average of 20.2% of their body weight, while those who took semaglutide lost an average of 13.7%. The participants who took tirzepatide also saw their waist sizes decrease by over five centimetres more on average than those taking semaglutide.
Side effects of tirzepatide vs semaglutide
Most common side effects of Mounjaro and Ozempic are fairly mild and tend to occur most frequently during the first few weeks of treatment, then gradually become less severe. This is because the body is adjusting.
Among the most commonly reported side effects are:
- Nausea and vomiting
- Constipation or diarrhoea
- Bloating
- Changes in appetite
Other side effects people may experience include fatigue, dizziness, headaches, heartburn and indigestion.
The 2025 trial indicated that there wasn’t much difference between Mounjaro and Ozempic, with almost four in five people (between 77% and 79%) experiencing at least one side effect. About 6% of people taking tirzepatide and 8% taking semaglutide stopped before the end of the study due to side effects.
If you’re taking one medication and you’re struggling with the side effects, speaking to a clinician could help you. You may be able to switch to a different medication to see if it improves your symptoms.
What’s the cost in the UK?
The UK pricing of Ozempic and Mounjaro can vary by provider, dosage and region. You’re paying for the branded prescription drug itself, as well as the work that goes into approving the dose, managing it and monitoring treatment over time.
The average cost of Mounjaro in the UK can vary, but it can be between about £150 and £350 per month, depending on your provider. Ozempic, which is more established in the UK, can be slightly cheaper at £150 to £250, but again, it can vary.
Ozempic is licensed in the UK to treat type 2 diabetes, while Mounjaro is licensed to treat both type 2 diabetes and to help people lose weight. Wegovy, another drug containing semaglutide, is licensed to help people with weight loss.
Many patients consider GLP-1 treatments to be value for money in the long run due to the convenience, effectiveness and support provided. So, if you’re considering starting on a GLP-1 medication, both Mounjaro and Ozempic could be worth considering. If you’d like to find out more, it’s best to speak to your doctor or a clinician.
For more information, visit the Virtual Slimming Clinic Blog. We have a wealth of resources just like this one, perfect for anyone looking to enhance their perspective on medicated weight loss.
Frequently asked questions
Are Mounjaro and Ozempic the same thing?
No – Mounjaro and Ozempic are both GLP-1 medications that can be used to help people manage type 2 diabetes and lose weight, but they have differences. Mounjaro contains the active ingredient tirzepatide, while Ozempic contains semaglutide.
Can I switch from Ozempic to Mounjaro?
You may be able to switch between GLP-1 medications under medical guidance. If it’s something you’re thinking about, it’s best to speak to your prescriber.
Is Mounjaro or Ozempic more effective for weight loss?
Clinical trials have found that Mounjaro could be more effective, particularly at higher doses, but this may not be the case for every patient.
