Mounjaro’s active ingredient is tirzepatide; Ozempic’s is semaglutide, which is the same active ingredient found in Wegovy. Both work by mimicking gut hormones that reduce appetite and slow digestion, and both are taken as a weekly self-injection (although there is now a Wegovy pill).
Where they differ is licensing and mechanism: Ozempic is approved in the UK only for type 2 diabetes, while Mounjaro is licensed for weight loss outright, and its dual-hormone action tends to produce stronger average results than semaglutide-based treatment in head-to-head trials. This guide walks through what the evidence shows, how the two compare on side effects and cost, and, since Ozempic itself isn’t an option for UK weight loss, what you may be prescribed instead.
Key takeaways
- Ozempic isn’t licensed for weight loss in the UK: it’s approved only for type 2 diabetes. Its weight-loss equivalent, made by the same manufacturer with the same active ingredient (semaglutide), is called Wegovy
- Mounjaro (tirzepatide) is licensed for weight loss in the UK: it works on two gut hormone receptors rather than one, which is why it tends to outperform semaglutide in head-to-head trials
- In a large 2024 study of over 18,000 patients, Mounjaro users lost up to 7% more weight on average than those on semaglutide: that’s with more than double the likelihood of losing 15% or more of their body weight
- Both medications carry similar side effect profiles: they’re mainly gastrointestinal and neither is available to buy over the counter; both require a prescription following an online or in-person consultation.
Mounjaro vs Ozempic: at a glance
| Feature | Mounjaro | Ozempic / Wegovy |
|---|---|---|
| Active ingredient | Tirzapatide | Semaglutide |
| Licensed for weight loss in the UK? | Yes | No, Wegovy is |
| Mechanism | GLP-1 and GLP receptor agonist | GLP-1 receptor agonist |
| Administration | Weekly self injection | Weekly self injection (but there is a Wegovy pill) |
| Average weight loss | Up to 7% more than semaglutide in head-to-head trials | 19% over 72 weeks, with diet and exercise |
| Available through CheqUp? | Yes | Yes (Wegovy, not Ozempic) |
Because Ozempic isn’t licensed for weight loss in the UK, we don’t prescribe it for that purpose and neither does any reputable UK provider.
How Mounjaro and Ozempic work
Both medications belong to a class of drugs that mimic natural gut hormones to reduce appetite and slow digestion, which is why users tend to feel fuller for longer and eat less without consciously trying to.
The difference is in how many hormone pathways each drug targets:
- Ozempic (semaglutide) mimics one hormone: GLP-1 (glucagon-like peptide-1), which helps regulate blood sugar and appetite.
- Mounjaro (tirzepatide) mimics two hormones: GLP-1 and GIP (glucose-dependent insulinotropic polypeptide), a dual action that appears to produce a stronger appetite-suppressing effect for many people.
This dual mechanism is the main reason Mounjaro tends to edge ahead of semaglutide-based treatments in clinical trials, though individual response varies: some people do better on one than the other regardless of the headline averages.
What the evidence shows
The clearest head-to-head evidence comes from a large study published in JAMA Internal Medicine, which followed over 18,000 adults with type 2 diabetes for up to a year, split evenly between tirzepatide (Mounjaro) and semaglutide.
The results consistently favoured Mounjaro:
- 5% weight loss: achieved by 82% of Mounjaro patients vs 66% on semaglutide
- 10% weight loss: around 60% on Mounjaro vs just under 40% on semaglutide
- 15% weight loss: 42% on Mounjaro vs 18% on semaglutide
Across three, six, and 12 months, Mounjaro patients lost between 2.4% and 6.9% more body weight on average than those on semaglutide at each interval, and were roughly twice as likely to lose 15% or more of their starting weight over the year.
Importantly, this extra effectiveness didn’t come with a meaningful increase in gastrointestinal side effects. The study found no significant difference in rates of nausea, diarrhoea, or vomiting between the two groups. It’s also worth noting the study population had type 2 diabetes; results in people without diabetes, which is who most UK weight-loss patients are, are expected to follow a similar pattern, but aren’t identical, and further trials are ongoing.
Side effects: Mounjaro vs Ozempic
Both medications share a similar side-effect profile, since they work in a related way. Most Wegovy or Mounjaro side effects, for example, settle within the first few weeks as your body adjusts, and are more common at higher doses or during dose increases.
| Side effect | Mounjaro | Ozempic / Wegovy |
|---|---|---|
| Nausea | Common | Common |
| Diarrhoea | Common | Common |
| Constipation | Common | Common |
| Vomiting | Less common | Less common |
| Heartburn / acid reflux | Less common | Less common |
| Fatigue | Reported | Reported |
Serious Mounjaro or Wegovy side effects are rare with both medications, but can include inflammation of the pancreas or a severe allergic reaction.
Licensing, eligibility, and availability in the UK
This is where the two medications diverge:
- Mounjaro is licensed by the MHRA for weight loss in adults with obesity, or overweight adults with a related health condition, as well as for type 2 diabetes
- Ozempic is licensed only for type 2 diabetes in the UK
- Wegovy has the same active ingredient as Ozempic (semaglutide), but has different licensing. It is the medication approved for weight loss in the UK
Privately, eligibility is typically based on:
- Being 18 or over
- A BMI of 30+, or 27+ with a weight-related health condition (such as high blood pressure or type 2 diabetes)
On the NHS, criteria are stricter, generally requiring a BMI of 40+ (or 37.5+ for some ethnic groups) alongside multiple weight-related health conditions, and access is usually through a specialist weight management service rather than a GP directly.
Cost in the UK
Private pricing for both treatments typically follows the dose you’re on, since both are titrated up gradually over several weeks. Generally, Mounjaro is at a higher price point than Wegovy at equivalent stages of treatment, though exact figures shift as manufacturer pricing changes.
Which is right for you?
Neither medication is objectively ‘better’ for everyone, as it depends on your starting point, your priorities and how your body responds.
Mounjaro may suit you if:
- You want the treatment with the strongest average weight-loss results in head-to-head trials
- You’ve tried semaglutide-based treatment before, with limited results
Wegovy may suit you if:
- You’d prefer a treatment with a longer real-world track record
- You’re currently on it and it’s working well: switching isn’t usually necessary just because Mounjaro has a slight edge on average
- You prefer taking a pill over an injection
If you’re already comparing weight loss treatments and considering switching, that’s a conversation to have with a provider, rather than a decision to make from research alone. That’s because your medical history, current dose, and reasons for switching all matter.
FAQs
Is Mounjaro the same as Ozempic?
No, they’re different medications with different active ingredients. Mounjaro (tirzepatide) targets two hormone receptors; Ozempic (semaglutide) targets one. Ozempic also isn’t licensed for weight loss in the UK (Wegovy, which shares its active ingredient, is).
Is Mounjaro stronger than Ozempic?
In UK-specific terms, Mounjaro tends to produce greater average weight loss than semaglutide-based treatment (Ozempic/Wegovy) in clinical trials, largely due to its dual-hormone action. ‘Stronger’ isn’t quite the right word, since the two work slightly differently, but on average, Mounjaro users lose more weight.
Can I get Ozempic for weight loss in the UK?
Not through reputable providers. Ozempic is licensed in the UK only for type 2 diabetes. If you want the same active ingredient (semaglutide) prescribed specifically for weight loss, that’s Wegovy.
Can I switch from Wegovy to Mounjaro, or vice versa?
Yes, under clinical supervision, but not immediately — semaglutide can take several weeks to fully clear your system, and you should never take two GLP-1 medications at the same time.
Is Mounjaro or Ozempic/Wegovy cheaper in the UK?
Pricing varies by dose and provider. As a general pattern, Wegovy tends to be the more affordable option at comparable stages of treatment, though this is subject to change.
Ready to find out which treatment suits you?
Take our 2-minute eligibility check to see whether Mounjaro or Wegovy could be right for you, with a CheqUp Clinician making the final call based on your full health profile.
Results vary between individuals and cannot be guaranteed. The suitability of any product or treatment is a professional prescribing decision made by a qualified clinician following an individual consultation — not a guarantee of eligibility or outcome. This content is for general information only and is not a substitute for professional medical advice. As part of the assessment, you will be asked for your GP’s details, and relevant information may be shared with them, with your consent, where clinically appropriate.
