Wegovy vs Mounjaro: A complete UK comparison guide 

What are Wegovy and Mounjaro?

Before comparing the two treatments, it is worth understanding what each one is, who it is licensed for, and how it is currently accessed in the UK.

Wegovy (semaglutide 2.4 mg, manufactured by Novo Nordisk) is a once-weekly injectable GLP-1 receptor agonist, licensed in the UK for chronic weight management in adults with a BMI of 30 or above, or 27 or above with a weight-related health condition. It is also available as Ozempic at lower doses for type 2 diabetes. 

Mounjaro (tirzepatide, manufactured by Eli Lilly) is a once-weekly injectable dual GIP and GLP-1 receptor agonist, licensed in the UK for type 2 diabetes and weight management under the same BMI criteria. NHS access for weight loss is available through specialist tier 3/4 services from June 2025 onwards, though eligibility criteria are strict. For most people, both treatments are accessed via private prescription.

How they work: single vs dual mechanism

Perhaps the most fundamental difference between the two treatments is the single vs. dual mechanism. Let’s break it down. 

Wegovy activates GLP-1 receptors only. GLP-1 is a gut hormone released after eating that stimulates insulin secretion, suppresses glucagon, slows gastric emptying, and signals the brain to reduce hunger. Semaglutide mimics this hormone, producing meaningful appetite suppression and blood sugar regulation.

Mounjaro activates both GLP-1 and GIP receptors simultaneously. GIP is a second gut hormone that enhances insulin secretion, improves insulin sensitivity, and influences how the body handles energy at a cellular level. Activating both pathways together produces a broader metabolic effect than either hormone could achieve alone.

Efficacy: what the clinical trials show

Clinical trials are the most reliable way to compare how well two treatments work. The data for Wegovy and Mounjaro is now more complete than for almost any other weight-loss medicines, thanks to years of large-scale studies and, crucially, the first direct head-to-head trial published in 2025.

SURMOUNT-5: the head-to-head trial

The most important study for this comparison is SURMOUNT-5, published in the New England Journal of Medicine in May 2025. The first direct head-to-head trial of its kind, it ran over 72 weeks and compared tirzepatide and semaglutide in adults without type 2 diabetes. Participants on Mounjaro 15 mg lost an average of 20.2% of their body weight, compared to 13.7% on Wegovy 2.4 mg. Around 45% of Mounjaro participants achieved at least 25% weight loss, compared to 19% on Wegovy, and waist circumference reduction was greater too: 18.4 cm vs 13 cm. 

The Wegovy 7.2 mg development

This comparison shifted in January 2026. On 6 January 2026, the MHRA licensed a new 7.2 mg dose of Wegovy, three times higher than the previously available 2.4 mg dose. The Phase 3b STEP UP trial found that patients lost an average of 20.7% of their body weight with the 7.2 mg dose, compared to 17.5% with the standard 2.4 mg dose over 72 weeks. Significantly, 33.2% of patients on the higher dose achieved 25% or more weight loss. 

This means that at maximum doses, Wegovy 7.2 mg and Mounjaro 15 mg now produce broadly comparable average weight loss (20.7% vs 20.2%). However, Wegovy 7.2 mg is not a starting dose. It is intended for patients who have completed the full titration pathway to 2.4 mg and continue to experience persistent hunger or have reached a weight plateau on lower doses. 

Key trial data

All figures represent average weight loss in adults with obesity or overweight. Individual results vary. Always discuss realistic expectations with your prescriber.

Dosage: full titration schedules

Both treatments follow a gradual titration schedule, starting at a low dose to minimise side effects and increasing every four weeks.

Wegovy titration schedule

Mounjaro titration schedule

Both are once-weekly subcutaneous injections, self-administered into the abdomen, outer thigh, or upper arm.

Switching between treatments

Switching from one treatment to the other is possible under medical supervision. There is no evidence of harmful interactions from switching. Your UK-registered prescriber will assess your treatment history and advise on the most appropriate starting dose for the new medication.

Side effects: how do they compare?

The side effect profiles of Wegovy and Mounjaro are broadly similar, as both activate GLP-1 receptors. The table below summarises the key comparisons based on MHRA prescribing information and SURMOUNT-5 trial data.

The most commonly reported adverse events in SURMOUNT-5 for both treatments were gastrointestinal-related and were generally mild to moderate in severity. There is some evidence that vomiting and burping are reported slightly more frequently with Mounjaro, though neither treatment is clearly better tolerated across all measures.

A full medication review with your UK-registered prescriber is essential before starting either treatment. Any suspected side effects from either medicine should be reported to the MHRA via the Yellow Card scheme.

Cost comparison: Wegovy vs Mounjaro in 2026

Before September 2025, Mounjaro and Wegovy were broadly similar in price across most UK private providers. That changed when Eli Lilly increased Mounjaro's UK wholesale price by up to 170%, aligning it with other developed markets. Wegovy is now meaningfully cheaper at every dose stage for most providers. The gap is roughly £600 to £1,100 over a full year of treatment at maintenance doses. 

Typical monthly private prescription prices (2026)

Prices based on GPhC-registered UK provider data, April 2026. Always confirm current pricing and exactly what is included before ordering.

NHS access

Both treatments are available on the NHS for eligible patients, at the standard prescription charge of £9.90 per item in England (free in Scotland, Wales, and Northern Ireland for eligible patients). In both cases, NHS access is restricted to specialist services with strict eligibility criteria and significant waiting times in most regions. Speak to your GP about whether a referral may be appropriate.

Real-world patient experience: common themes

Clinical trial data shows what both treatments can achieve under controlled conditions. In real-world UK settings, a number of consistent themes emerge from patient-reported outcomes.

With Mounjaro, patients commonly report:

• Rapid and sustained reduction in appetite, often described as "food noise" disappearing
• Faster and more pronounced weight loss, particularly at higher doses
• Slightly more pronounced gastrointestinal side effects in the early weeks, especially burping and nausea
• Concerns about cost following the 2025 price increase, prompting some to switch to Wegovy

With Wegovy, patients commonly report:

• Gradual, steady weight loss that builds over the titration period
• Good tolerability for most people at standard doses
• More manageable monthly costs, particularly post-2025
• Some patients plateau at 2.4 mg and benefit from the new 7.2 mg dose option

In both cases, patients who combine treatment with structured dietary changes and regular physical activity consistently report better outcomes than those who rely on medication alone.

Who might benefit more from each treatment?

Neither treatment is objectively better for every person. The right choice depends on your individual health profile, goals, budget, and tolerability. The guidance below is illustrative, not prescriptive; always discuss with your UK-registered prescriber.

Mounjaro may be worth discussing if you:

• Have type 2 diabetes and would benefit from the dual glucose-lowering and weight-loss effect
• Have a higher starting BMI and are aiming for the greatest possible weight reduction
• Are not primarily driven by cost and prioritise maximum efficacy at standard doses
• Have already tried a GLP-1 only treatment with limited results

Wegovy may be worth discussing if you:

• Are primarily focused on weight management without a diabetes diagnosis
• Are cost-conscious, particularly at maintenance doses post-2025
• Have already been established on semaglutide (Ozempic) for diabetes and are transitioning to a higher weight-management dose
• Are a candidate for the new 7.2 mg dose and want results comparable to Mounjaro at a lower cost

Final thoughts

The gap between Wegovy and Mounjaro has narrowed considerably in 2026. Mounjaro still holds an efficacy advantage at standard doses, but the approval of Wegovy 7.2 mg means that for patients who titrate fully, results are now broadly comparable. The more meaningful difference for most private patients is cost, where Wegovy has a clear advantage following the 2025 Mounjaro price increase.

Ultimately, the best choice is the one that is clinically appropriate for you, sustainable over the long term, and supported by a prescriber who knows your health history. If you are weighing up the options, start that conversation with your GP or a UK-registered prescriber rather than deciding on the basis of trial averages alone.

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