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Wegovy vs Mounjaro: which weight loss injection is better in the UK?

Wegovy (semaglutide) and Mounjaro (tirzepatide) are the two weekly weight loss injections you can be prescribed in the UK. This guide puts the published trial results side by side, including the only head to head study, then covers side effects, dose steps, the heart benefit licence, NHS access, what each costs privately and how switching between them works. iGovy is independent and does not sell either medicine.

  • Last checked 3 Nov 2026
  • Author: Nick Johnson, Independent Prescription Pricing Analyst
  • Trial data from peer reviewed papers only
  • Wegovy prices live from GPhC verified pharmacies
  • iGovy does not sell medicines

The short answer

On the trial numbers Mounjaro produces more weight loss than Wegovy 2.4mg: in the head to head SURMOUNT-5 study people lost 20.2% of their body weight on tirzepatide against 13.7% on semaglutide 2.4mg over 72 weeks. Wegovy's newer 7.2mg dose closes much of that gap, reaching about 20.7% in its own trial, and Wegovy is the only one of the two with a UK licence for reducing the risk of heart attack and stroke in eligible adults.

Side effects are broadly the same for both. On price, both rise with the dose, and since Mounjaro's manufacturer price rise in September 2025 the higher Mounjaro doses have generally cost more per month than Wegovy 2.4mg. The right choice depends on how much weight you need to lose, your heart history, what you can tolerate and what you can afford every month for a year or more. That decision sits with your prescriber. This page gives you the evidence for that conversation.

What is the difference between Wegovy and Mounjaro?

They are different molecules from different companies that work in related but not identical ways.

Wegovy and Mounjaro at a glance
WegovyMounjaro
Active ingredientSemaglutideTirzepatide
How it worksGLP-1 receptor agonist: mimics one gut hormone that slows stomach emptying and reduces appetiteDual GIP and GLP-1 receptor agonist: acts on two gut hormone receptors
ManufacturerNovo NordiskEli Lilly
How it is takenOnce weekly injection under the skinOnce weekly injection under the skin
Dose steps0.25mg, 0.5mg, 1mg, 1.7mg, 2.4mg, then 7.2mg for some people2.5mg, 5mg, 7.5mg, 10mg, 12.5mg, 15mg
PenFlexTouch multi dose pen, four weekly doses (7.2mg comes as single use pens)KwikPen multi dose pen, four weekly doses
UK licencesWeight management; reducing the risk of major cardiovascular events in adults with established heart disease and overweight or obesityWeight management; type 2 diabetes
NHS routeNICE TA875, specialist weight management services, maximum two yearsNICE TA1026, phased primary care rollout from June 2025
Licence and dose details from the UK Summaries of Product Characteristics and NICE guidance listed in the sources. Ozempic is semaglutide too but is licensed for type 2 diabetes, not weight management. See Wegovy vs Ozempic.

The practical upshot of the mechanism difference is that tirzepatide's second hormone pathway appears to add weight loss on top of what GLP-1 alone achieves. Whether that matters for you depends on how much weight you are aiming to lose and how you respond, which is individual. Background on how semaglutide works is on what is Wegovy.

Wegovy vs Mounjaro weight loss: what the trials show

The numbers below are average total body weight loss in the pivotal trials, in adults with obesity or overweight and without diabetes, taken with diet and exercise support. They are averages: some people lose considerably more, some less, and a minority do not respond to either.

14.9%

Wegovy 2.4mg, STEP 1, 68 weeks, against 2.4% on placebo (Wilding et al., NEJM 2021)

20.7%

Wegovy 7.2mg, STEP UP, 72 weeks, against 17.5% on 2.4mg in the same trial (Wharton et al., Lancet Diabetes and Endocrinology 2025)

20.9%

Mounjaro 15mg, SURMOUNT-1, 72 weeks, against 3.1% on placebo, with 15% at 5mg and 19.5% at 10mg (Jastreboff et al., NEJM 2022)

The head to head trial: SURMOUNT-5

Cross trial comparisons are unreliable because the trials recruited different people and ran for different lengths of time. SURMOUNT-5 is the study that matters, because it randomised 751 adults with obesity to either tirzepatide (10mg or 15mg) or semaglutide 2.4mg and followed them for 72 weeks.

20.2%

Average weight loss on Mounjaro at 72 weeks

13.7%

Average weight loss on Wegovy 2.4mg at 72 weeks

32%

Of Mounjaro participants lost at least a quarter of their body weight, against 16% on Wegovy

Published by Aronne and colleagues in the New England Journal of Medicine in 2025, the trial found tirzepatide delivered roughly 47% more relative weight loss than semaglutide 2.4mg, with a larger drop in waist circumference as well. Two caveats keep this honest. First, the semaglutide arm was capped at 2.4mg. The 7.2mg dose did not exist yet, and its own trial result of about 20.7% sits close to tirzepatide's. Second, SURMOUNT-5 was funded by Eli Lilly, which does not invalidate a randomised trial published in a top journal but is worth knowing.

What this means in practice: if you have a large amount of weight to lose and tolerate the higher doses, Mounjaro has the stronger evidence at 2.4mg equivalent comparisons, and Wegovy 7.2mg is the semaglutide answer to that gap. If your target is more modest, both medicines comfortably exceed it on average and the other factors below become more important than the headline percentage.

Heart benefit: where Wegovy has the licence

The SELECT trial (Lincoff et al., NEJM 2023) followed more than 17,000 adults with established cardiovascular disease and overweight or obesity, but without diabetes, for over three years. Semaglutide 2.4mg reduced the combined risk of cardiovascular death, heart attack and stroke by 20% compared with placebo. On the back of that, the MHRA extended Wegovy's UK licence to include reducing the risk of major adverse cardiovascular events, and NICE has recommended it for that use in eligible adults.

Mounjaro does not currently hold an equivalent UK licence for cardiovascular risk reduction in people without diabetes. Its outcome trials are ongoing or reported in different populations. For someone with a history of heart attack, stroke or peripheral artery disease that licence is a real, evidence based reason a prescriber may favour Wegovy even though Mounjaro produces more weight loss. More on this in Wegovy and heart disease.

Wegovy vs Mounjaro side effects

Because both medicines act on the GLP-1 receptor, their side effect profiles overlap heavily. The most common effects of both are gastrointestinal and cluster around dose increases:

  • Nausea, diarrhoea, constipation and vomiting are the most frequently reported for both. In SURMOUNT-5 these were the leading side effects in both arms and were mostly mild to moderate.
  • Stopping because of side effects was uncommon in both arms of SURMOUNT-5: 6.1% on tirzepatide and 8.0% on semaglutide.
  • Shared class warnings: acute pancreatitis, gallbladder disease, low blood sugar when combined with insulin or a sulfonylurea, and dehydration from persistent vomiting or diarrhoea. Both leaflets tell you to seek urgent help for severe, persistent stomach pain.
  • Injection site reactions are more often reported with Mounjaro in its trials, though they are usually minor.
  • Individual tolerance differs. A meaningful number of people who cannot settle on one medicine do well on the other, which is one of the common reasons for switching.

Neither medicine is suitable in pregnancy, while breastfeeding, or for people with a personal or family history of medullary thyroid cancer. The full Wegovy list, taken straight from the patient leaflet, is on the Wegovy side effects body map, with separate guides to nausea, pancreatitis and gallstones. Alcohol interacts with both in the same way, covered on Wegovy and alcohol.

Dose steps and how the plans compare

Both medicines start low and step up every four weeks to limit stomach side effects, and both pens hold four weekly doses, so one pen is one month on either medicine.

Standard titration on each medicine (one pen per step)
MonthWegovyMounjaro
Month 10.25mg2.5mg
Month 20.5mg5mg
Month 31mg7.5mg
Month 41.7mg10mg
Month 5 onwards2.4mg maintenance; 7.2mg available on prescriber decision12.5mg, then 15mg; many people are maintained at 5mg, 10mg or 12.5mg
Prescribers can hold you at any step for longer, and Mounjaro in particular is often kept at a middle dose rather than pushed to 15mg. Wegovy's plan is explained step by step on Wegovy dose steps and the 7.2mg pens on the 7.2mg explainer.

One structural difference worth knowing before you pick: Wegovy has a single standard maintenance dose (2.4mg) with 7.2mg as an escalation, so most people end up buying the same pen every month. Mounjaro has a wider spread of maintenance doses, which gives more room to settle at a lower, cheaper dose if it is enough for you, or to escalate if it is not.

Wegovy vs Mounjaro price in the UK

Both are priced per pen and the price rises with the dose, so a fair comparison is your likely maintenance dose on each, delivered, over a year. iGovy holds no hand typed prices: the Wegovy cards below are generated from the price database on every page load, and Mounjaro prices are tracked the same way on iGovy's sister site monj.co.uk.

Cheapest Wegovy today, maintenance doses

Last checked 3 Nov 2026

Every Wegovy dose, cheapest first, is on the Wegovy price comparison, and what a pen, a month and a year cost is worked through on Wegovy injection price.

Mounjaro prices, live

Monj tracks every Mounjaro dose across the same GPhC verified pharmacies, checked daily, with the manufacturer price rise of September 2025 already reflected in the live figures.

Compare Mounjaro prices on Monj

Three things decide which works out cheaper for you rather than in general:

  • Your maintenance dose. Wegovy 2.4mg against Mounjaro 10mg to 15mg is the usual comparison, and at those doses Mounjaro has generally cost more per month since September 2025. Someone maintained on Mounjaro 5mg changes that picture.
  • The first four months. Titration pens are cheaper on both, so year one costs less than year two on either medicine.
  • The pharmacy. The spread between the cheapest and dearest verified pharmacy for the same pen is larger than the gap between the two medicines at many doses. Compare delivered prices, use the pharmacy discount codes once, and read the maintenance pharmacies list if you expect to stay on treatment after your BMI falls.

The wider market, including tablets, is on compare weight loss injection prices.

NHS access: Wegovy vs Mounjaro

Both are NICE approved, but through different routes and neither is easy to get.

  • Wegovy is recommended under NICE TA875 for adults with at least one weight related condition and a BMI of 35 or more (30 to 34.9 where the person meets specialist referral criteria, and lower thresholds for some ethnic groups), prescribed within a specialist weight management service and for a maximum of two years. NICE has also recommended it for cardiovascular risk reduction in eligible adults.
  • Mounjaro is recommended under NICE TA1026 for adults with a BMI of 35 or more and at least one weight related condition, and is being rolled out in primary care in phases from June 2025, starting with people with the highest BMI and the most conditions. Full rollout is planned over several years.

In England an NHS prescription item costs £9.90 for 2026/27 and prescriptions are free in Scotland, Wales and Northern Ireland, so if you qualify the NHS route is far cheaper than private. In practice most people using either medicine in the UK pay privately, which is why the eligibility rules on Wegovy BMI requirements matter for the private route too: online pharmacies apply the licence thresholds, not the tighter NICE ones.

Switching between Wegovy and Mounjaro

People switch in both directions, usually because of side effects, cost, supply, or a plateau. There is no official conversion table between semaglutide and tirzepatide doses, so switching is a prescriber decision, not something to do by mail order arithmetic.

  • Timing. Stop one medicine and start the other on the next scheduled injection day, so there is no week with two doses on board.
  • Starting dose. Prescribers typically do not jump to the top dose of the new medicine. A common approach after a stable period at maintenance is to start a step or two below the equivalent position and titrate back up, watching for stomach side effects.
  • Pharmacy switching. Changing medicine often means changing provider. The switching pharmacy guide covers doing that without a gap in supply.

The Mounjaro to Wegovy direction, including what prescribers consider, is covered in detail on switching from Mounjaro to Wegovy.

Which should you choose?

Prescribers weigh the same handful of factors. Here is how they tend to fall.

Wegovy tends to suit people who

  • have a history of heart attack, stroke or cardiovascular disease, because it holds the UK licence for reducing that risk
  • want the lower monthly cost at a standard maintenance dose
  • prefer a simpler plan with one maintenance pen, with 7.2mg available if 2.4mg stalls
  • did not tolerate tirzepatide

Mounjaro tends to suit people who

  • have a large amount of weight to lose and want the strongest trial evidence for average weight loss
  • also have type 2 diabetes, where it is licensed and widely used
  • want a wider range of maintenance doses to settle at
  • did not tolerate or plateaued on semaglutide
Neither is a self service choice. Both are prescription only medicines. A GPhC registered pharmacy's prescriber will assess your BMI, medical history and current medicines before either is supplied, and iGovy only lists pharmacies that pass GPhC verification.

Wegovy vs Mounjaro questions

Is Mounjaro better than Wegovy for weight loss?

In SURMOUNT-5, the only head to head trial, Mounjaro produced 20.2% average weight loss at 72 weeks against 13.7% on Wegovy 2.4mg. Wegovy 7.2mg, launched after that trial, reached about 20.7% in its own study, so the gap at the top doses is narrower than the headline.

What is the difference between Wegovy and Mounjaro?

Wegovy is semaglutide, a GLP-1 receptor agonist from Novo Nordisk. Mounjaro is tirzepatide from Eli Lilly and acts on both the GLP-1 and GIP receptors. Both are weekly injections, but only Wegovy is licensed in the UK for cardiovascular risk reduction.

Is Wegovy the same as Mounjaro?

No. They are different active ingredients with different mechanisms, dose steps and licences, though they are used for the same purpose and share most side effects.

Which is cheaper, Wegovy or Mounjaro?

Compare your maintenance dose on each. The Wegovy cards on this page are live, and Mounjaro prices are live on monj.co.uk. Since September 2025 the higher Mounjaro doses have generally cost more per month than Wegovy 2.4mg.

Are the side effects the same?

Largely. Nausea, diarrhoea, constipation and vomiting lead for both, mostly around dose increases, and both share the class warnings on pancreatitis and gallbladder problems. Tolerance is individual.

Can I switch between them?

Yes, with a prescriber. There is no official dose conversion, so the usual approach is to swap on the next injection day and restart at a dose the prescriber chooses.

Can I take both together?

No. They act on the same receptor pathway and are never prescribed together.

Which is available on the NHS?

Both, with limits: Wegovy through specialist services under TA875 for up to two years, Mounjaro through a phased primary care rollout under TA1026. Most UK users of either pay privately.

Sources