Mounjaro vs Wegovy UK: Full Comparison

Last updated: April 2026

If you are weighing up Mounjaro against Wegovy, you are not alone — it is one of the most common questions among people researching injectable weight-loss medication in the UK. Both are once-weekly injections, both are prescription-only, and both have strong clinical evidence behind them. But they differ in how they work, what they cost, and what the trial data shows. This guide sets out the key differences clearly and without bias. LetsLoseWeight is an independent comparison site — we are not affiliated with any pharmacy, manufacturer, or provider.

What are Mounjaro and Wegovy?

Mounjaro is the brand name for tirzepatide, manufactured by Eli Lilly. It was licensed by the MHRA for weight management in adults in November 2023. Wegovy is the brand name for semaglutide at weight-management doses, manufactured by Novo Nordisk, and has been available in the UK for weight management since 2023.

Both are administered as once-weekly subcutaneous injections and are available privately from GPhC-registered UK providers. Both require a prescription from a registered clinician following a clinical assessment.

How do they work — and what is the difference?

This is where the two medications diverge most clearly at a scientific level.

Wegovy (semaglutide) is a GLP-1 receptor agonist. It mimics GLP-1, a gut hormone released after eating that signals fullness to the brain, slows gastric emptying, and reduces appetite. This single-pathway action has been the basis of GLP-1 medications for over a decade.

Mounjaro (tirzepatide) is a dual GIP and GLP-1 receptor agonist — it activates both GLP-1 and GIP receptors simultaneously. GIP is a second gut hormone involved in insulin regulation, fat metabolism, and energy balance. By targeting both pathways, tirzepatide produces a broader hormonal effect than semaglutide alone.

This dual mechanism is widely believed to be the reason tirzepatide produced greater average weight loss than semaglutide in clinical trials — though the two medications have not yet been compared head-to-head in a large-scale weight-management trial.

What do the clinical trials show?

Clinical trial data is the most objective comparison point available, though it must be read carefully — different trials use different populations, different durations, and different methodologies.

Wegovy: In the STEP 1 trial, participants taking semaglutide 2.4mg lost an average of approximately 15–17% of their body weight over 68 weeks, compared to approximately 2–3% with placebo. These are trial results in a specific population — individual outcomes vary.

Mounjaro: In the SURMOUNT-1 trial, participants taking tirzepatide at the highest doses (10mg and 15mg) lost an average of approximately 20–22% of their body weight over 72 weeks, compared to approximately 2–3% with placebo. Again, these are trial results, not typical individual outcomes.

On average, the trial data shows greater weight loss with tirzepatide than semaglutide. However, no published head-to-head trial in a weight-management population has directly compared the two medications, so these figures come from separate studies with different designs. A prescriber can help you interpret what this means for your individual situation.

How do the doses compare?

Both medications use a gradual dose-escalation approach, starting low and increasing over several months.

Wegovy dose schedule:
0.25mg → 0.5mg → 1mg → 1.7mg → 2.4mg (standard maintenance)
A new 7.2mg dose is now available in the UK for eligible patients.

Mounjaro dose schedule:
2.5mg → 5mg → 7.5mg → 10mg → 12.5mg → 15mg

Mounjaro has more dose steps and a longer escalation period before reaching the full maintenance dose range. Both medications are titrated over several months under prescriber supervision — dose steps should never be skipped or self-managed.

How do the prices compare in the UK?

Price is one of the most practically significant differences between the two medications in the current UK private market.

Following an Eli Lilly UK price increase in September 2025, Mounjaro became more expensive than Wegovy at comparable dose stages. Based on current market data across GPhC-registered providers:

Wegovy approximate monthly costs:

0.25mg starter dose: approximately £129–£200
1.7mg–2.4mg maintenance: approximately £180–£300

Mounjaro approximate monthly costs:

2.5mg starter dose: approximately £130–£220
7.5mg–15mg maintenance: approximately £200–£375

At comparable stages of treatment, Wegovy is typically £50–£100 per month cheaper than Mounjaro. Over a full year, that difference can represent a saving of £600–£1,100.

For the most current prices across all GPhC-registered providers, see our Mounjaro price comparison and Wegovy price comparison pages.

Side effects — how do they compare?

The side effect profiles of Mounjaro and Wegovy are broadly similar, reflecting their shared GLP-1 mechanism. The most commonly reported effects for both medications are gastrointestinal, particularly during dose escalation.

Common to both:

Nausea
Vomiting
Diarrhoea
Constipation
Stomach discomfort or bloating

These effects are typically most pronounced when starting treatment or increasing the dose, and tend to improve as the body adjusts. Slower dose escalation can help manage them.

More serious effects (less common, relevant to both):

Pancreatitis
Gallbladder problems (including gallstones)
Increased heart rate

Both medications share contraindications including a personal or family history of certain thyroid tumours (medullary thyroid carcinoma), pregnancy, and active pancreatitis. Your prescriber will assess your individual risk profile before recommending either medication.

NHS availability — is there a difference?

For practical purposes, NHS access criteria are broadly the same for both medications. Both are available through NHS Tier 3 specialist weight management services, not through standard GP appointments. In England, eligibility typically requires a BMI of 35 kg/m² or above (or 30 kg/m² or above with a qualifying comorbidity such as type 2 diabetes or hypertension).

Waiting times for Tier 3 services are currently 12–18 months in many parts of England. Availability depends on local NHS Integrated Care Board funding decisions, which vary by region.

NHS prescription charges apply in England (currently £9.90 per item). Prescriptions are free in Scotland, Wales, and Northern Ireland.

How to choose — Mounjaro or Wegovy?

There is no single answer that applies to everyone. The right medication depends on your individual health profile, medical history, and what matters most to you. That said, here are the key considerations that typically shape the decision:

Consider Wegovy if: cost is a primary concern, you are earlier in your weight-loss journey and looking for a well-established option with a strong long-term evidence base, or your prescriber has clinical reasons to prefer semaglutide for your individual profile.

Consider Mounjaro if: the clinical trial data showing higher average weight loss at the highest doses is a significant factor for you, cost is less of a constraint, or your prescriber recommends it based on your individual assessment.

In all cases, the decision should be made with a qualified prescriber who can assess your full medical history, current medications, and personal goals. Neither medication is universally "better" — both are clinically significant options with strong evidence behind them.

Frequently Asked Questions

Is Mounjaro stronger than Wegovy?

In clinical trials, tirzepatide (Mounjaro) produced greater average weight loss than semaglutide (Wegovy) at the highest doses — approximately 20–22% vs 15–17% of body weight. However, these are results from separate trials with different designs, not a direct head-to-head comparison. Individual results vary significantly. Whether one is "stronger" for a specific person is a clinical question best discussed with a prescriber.

Is Wegovy cheaper than Mounjaro in 2026?

Yes, in most cases. Following the Eli Lilly UK price increase in September 2025, Wegovy is now typically £50–£100 per month cheaper than Mounjaro at comparable dose stages — a difference of up to £1,100 over a full year of treatment.

Can I switch from Wegovy to Mounjaro (or vice versa)?

Switching between medications is possible but must be managed by your prescriber. The dose schedules are different, the active ingredients are different, and the clinical considerations for switching mid-treatment require professional oversight. Never switch without guidance from your prescriber.

Do Mounjaro and Wegovy have the same side effects?

Their side effect profiles are broadly similar — both commonly cause gastrointestinal symptoms such as nausea, vomiting, and diarrhoea, particularly during dose escalation. Both share the same serious but less common risks, including pancreatitis and gallbladder problems. Your prescriber will discuss individual risk factors with you.

Which medication is available on the NHS?

Both Mounjaro and Wegovy are available through the NHS, but only via Tier 3 specialist weight management services — not through standard GP appointments. Eligibility criteria and waiting times are broadly similar for both. See our Mounjaro UK guide and Wegovy UK guide for full details.

Is tirzepatide the same as Mounjaro?

Yes. Tirzepatide is the active ingredient; Mounjaro is the brand name. They are the same medication.

Is semaglutide the same as Wegovy?

Semaglutide is the active ingredient in both Wegovy and Ozempic. Wegovy is licensed specifically for weight management at higher doses. Ozempic is licensed for type 2 diabetes and is not the same product, even though both contain semaglutide.

Clinical note: This guide is for informational purposes only and does not constitute medical advice. It should not be used to self-diagnose, self-treat, or make decisions about starting, switching, or stopping any medication. Only a qualified, registered prescriber can assess your suitability for Mounjaro, Wegovy, or any other weight-loss medication. If you have questions about your treatment options, speak to your prescriber or a registered pharmacist.