Mounjaro vs Ozempic UK: 5 Key Differences for Weight Loss in 2026

Mounjaro and Ozempic are the two most talked-about weight loss injections in the UK right now, but they are not the same medication, they do not work the same way, and one of them is not even licensed for weight loss in this country. If you are trying to decide between these two GLP-1 treatments, here are the five differences that actually matter for your results, your wallet, and your eligibility.

In this article

• 1. How do Mounjaro and Ozempic actually work?
• 2. Which one is licensed for weight loss in the UK?
• 3. How much weight can you expect to lose?
• 4. What are the side effects?
• 5. How much do they cost in the UK?
• How to choose between Mounjaro and Wegovy
• Using your injection pen safely at home
• Frequently asked questions

1. How do Mounjaro and Ozempic actually work?

This is the most important difference. Ozempic contains semaglutide, which targets a single gut hormone called GLP-1. It slows stomach emptying, reduces appetite, and helps regulate blood sugar. Mounjaro contains tirzepatide, which targets two gut hormones: GLP-1 and GIP. This dual-action mechanism is why clinical trials have consistently shown greater weight loss with Mounjaro.

Think of it this way: Ozempic pulls one lever to reduce your appetite, while Mounjaro pulls two. GIP (glucose-dependent insulinotropic polypeptide) plays a separate role in fat metabolism and energy balance, giving tirzepatide an additional pathway that semaglutide alone does not have.

	Mounjaro (tirzepatide)	Ozempic (semaglutide)
Active ingredient	Tirzepatide	Semaglutide
Mechanism	Dual GIP + GLP-1	GLP-1 only
Manufacturer	Eli Lilly	Novo Nordisk
Dose range	2.5 mg to 15 mg weekly	0.25 mg to 2 mg weekly
Administration	Weekly subcutaneous injection	Weekly subcutaneous injection

2. Which one is licensed for weight loss in the UK?

This catches many people off guard. Ozempic is not licensed for weight loss in the UK. The MHRA has approved Ozempic only for the treatment of type 2 diabetes. If you see Ozempic being prescribed "for weight loss," it is being used off-label.

The weight loss version of semaglutide is called Wegovy, which uses the same active ingredient as Ozempic but at a higher dose (up to 2.4 mg, with 7.2 mg approved by the MHRA in January 2026). Wegovy has a specific MHRA licence for chronic weight management.

Mounjaro (tirzepatide), by contrast, holds MHRA licences for both type 2 diabetes and chronic weight management in adults with a BMI of 30 or above (or 27 and above with at least one weight-related condition). NICE approved tirzepatide for NHS specialist weight management services under Technology Appraisal TA1026.

So when people search "Mounjaro vs Ozempic for weight loss," the fairer clinical comparison is actually Mounjaro vs Wegovy.

3. How much weight can you expect to lose?

The landmark SURMOUNT-5 trial put this question to rest with a direct head-to-head comparison over 72 weeks. Participants on tirzepatide (Mounjaro) lost an average of 20.2% of their body weight, compared to 13.7% for those on semaglutide (Wegovy). That is a clinically significant gap of 47% more weight lost with Mounjaro.

To put that in real terms: for someone weighing 100 kg (about 15 st 10 lb), Mounjaro would typically produce around 20 kg of weight loss versus 14 kg on Wegovy over the same period.

Key results from the major clinical trials:

• SURMOUNT-1 (Mounjaro 15 mg): 22.5% average weight loss over 72 weeks; 96.3% of participants lost at least 5% of body weight
• STEP 1 (Wegovy 2.4 mg): 14.9% average weight loss over 68 weeks
• SURMOUNT-5 (head-to-head): Mounjaro 20.2% vs Wegovy 13.7% over 72 weeks

4. What are the side effects?

Both medications share a similar side-effect profile because they both act on gut hormones. The most common issues are gastrointestinal: nausea, diarrhoea, constipation, and reduced appetite (which is partly how they work). These tend to be worst during the dose-escalation phase and settle for most people within a few weeks.

In clinical trials, nausea affected approximately 32% of Mounjaro users compared to around 44% of Wegovy users. Injection-site reactions are possible with both and are generally mild.

Serious but rare risks for both include pancreatitis and gallbladder problems. Neither medication should be used during pregnancy or by anyone with a personal or family history of medullary thyroid carcinoma or Multiple Endocrine Neoplasia syndrome type 2. Always discuss your full medical history with your prescriber before starting either treatment.

5. How much do they cost in the UK?

Neither Mounjaro nor Wegovy is available over the counter. You will need a prescription from a GP, NHS specialist weight management service, or a regulated online pharmacy.

Private prescription costs (approximate, October 2026):

• Mounjaro: £129 to £334 per monthly pen, depending on dose and provider
• Wegovy: £83 to £285 per monthly pen, depending on dose and provider
• Ozempic: £150 to £250 per pen (off-label for weight loss; diabetes prescription only)

NHS access: Mounjaro is available through NHS specialist weight management services under NICE TA1026 for adults with a BMI of 35 or above who have at least one weight-related health condition. Wegovy is also available on the NHS under similar criteria. Ozempic is not approved for NHS weight management programmes.

Prices vary significantly between providers. Always check that your pharmacy is registered with the GPhC (General Pharmaceutical Council) before ordering online.

How to choose between Mounjaro and Wegovy

If weight loss is your primary goal, the clinical evidence currently favours Mounjaro. The SURMOUNT-5 head-to-head trial showed a clear advantage in both percentage of body weight lost and the proportion of people achieving meaningful weight loss targets.

That said, your prescriber will consider several factors: your BMI, existing health conditions (particularly type 2 diabetes), medications you are already taking, and your tolerance of GLP-1 medications if you have tried one before. Some patients respond better to semaglutide, and Wegovy is the more established option with a longer track record in the UK market.

Whichever treatment you and your prescriber choose, monitoring your blood pressure at home is a sensible step. Weight loss medications can affect cardiovascular parameters, and keeping a regular log helps your healthcare team adjust your treatment as needed.

Using your injection pen safely at home

Both Mounjaro and Wegovy are self-administered at home using a pre-filled injection pen. After each use, the needle must be disposed of safely in a sharps bin rather than in your household waste. This is a legal requirement under the Environmental Protection Act 1990.

A small sharps bin sits easily on a bathroom shelf or bedside table and lasts most users several months of weekly injections. Once full, you can arrange free collection through your local council's clinical waste service or return it to your pharmacy.

Frequently asked questions

Can I get Mounjaro on the NHS?

Yes. NICE approved tirzepatide (Mounjaro) for NHS specialist weight management services under TA1026. You will need a referral from your GP to a Tier 3 or Tier 4 weight management service and must meet the eligibility criteria: a BMI of 35 or above with at least one weight-related health condition. Waiting times vary by area.

Is Ozempic the same as Wegovy?

They contain the same active ingredient (semaglutide) made by the same company (Novo Nordisk), but they are licensed differently in the UK. Ozempic is approved only for type 2 diabetes at doses up to 2 mg. Wegovy is approved for chronic weight management at doses up to 2.4 mg (and 7.2 mg from January 2026). They are not interchangeable prescriptions.

How long do I need to take Mounjaro or Wegovy?

Both are intended as long-term treatments alongside diet and exercise. Clinical trials show that most people regain weight if they stop the medication. Your prescriber will review your progress regularly and discuss whether continued treatment is appropriate for you.

Do I need a sharps bin for my injection pen?

Yes. Used injection pen needles are classified as clinical waste and must be disposed of in a UN-approved sharps container. You should never place used needles in your household bin. Small sharps bins designed for home use start from £1.69 at Vena Cava and last several months of weekly injections.

Can I take Mounjaro and Ozempic together?

No. Both are GLP-1 receptor agonists and should never be combined. Taking two GLP-1 medications simultaneously significantly increases the risk of serious gastrointestinal side effects and hypoglycaemia. Your prescriber may switch you from one to the other, but you should never take both at the same time.