The most common version of this question — "which is better, Mounjaro or Wegovy?" — doesn't have a single clean answer. Both are weekly injections, both work on appetite through hormonal pathways, and both produce meaningful weight loss. What differs is their mechanism, their effectiveness ceiling, their price since September 2025, and the cardiovascular evidence behind each.
We'll go through each dimension in turn. Where the evidence clearly favours one, we'll say so. Where it's genuinely uncertain or individual, we'll say that too.
This article is information, not medical advice. Both medications are prescription-only. The right choice for you depends on your medical history, current medications, and clinical assessment — which this article cannot substitute for.
How they work differently
Both medications mimic hormones your body produces naturally after eating — hormones that signal fullness, slow digestion, and suppress appetite. The critical difference is which hormones they target.
Wegovy (semaglutide) targets one hormone: GLP-1 (glucagon-like peptide-1). GLP-1 tells your brain you're full, slows gastric emptying, and reduces the urge to eat. Wegovy is a GLP-1 receptor agonist — it activates that receptor more persistently than the hormone your body produces naturally.
Mounjaro (tirzepatide) targets two hormones: GLP-1 and GIP (glucose-dependent insulinotropic polypeptide). GIP was initially thought to be a minor player in appetite regulation, but research has shown it works synergistically with GLP-1. The combined effect appears to produce greater appetite suppression and broader metabolic impact than GLP-1 alone.
The dual-receptor mechanism of Mounjaro is why it tends to produce greater average weight loss than Wegovy — but it also means it acts on more systems simultaneously, which has implications for both efficacy and side effects.
Which is more effective?
At their standard maximum doses, Mounjaro produces greater average weight loss. The landmark SURMOUNT-5 trial — published in the New England Journal of Medicine in 2025 — was the first head-to-head comparison, and the results clearly favoured tirzepatide: roughly 20% weight loss versus 14% for semaglutide at its then-maximum 2.4mg dose.
Then in January 2026, the MHRA approved Wegovy 7.2mg — a higher dose that changes the picture significantly. The STEP UP trial showed this new dose achieving around 20.7% weight loss, essentially matching Mounjaro's headline figure.
What does this mean in practice? A few things worth understanding:
- The 7.2mg Wegovy dose is only for patients who have already reached and tolerated 2.4mg — it's not a starting dose.
- The SURMOUNT-5 and STEP UP trials used different populations and protocols, so the numbers aren't perfectly comparable.
- Population averages obscure enormous individual variation. Some people respond exceptionally well to semaglutide; others barely respond at all and do much better on tirzepatide — and vice versa.
- The question isn't just how much you lose, but whether you can tolerate the medication consistently enough to achieve it.
| Metric | Mounjaro (tirzepatide) | Wegovy (semaglutide) |
|---|---|---|
| Mechanism | GLP-1 + GIP dual agonist | GLP-1 agonist |
| Max licensed dose (UK) | 15mg weekly | 7.2mg weekly (from Jan 2026) |
| Average weight loss (max dose) | ~20% body weight | ~14% (2.4mg), ~21% (7.2mg) |
| Head-to-head trial (SURMOUNT-5) | Favours tirzepatide | vs 2.4mg only — predates 7.2mg |
| Individual variation | High for both — response is not predictable in advance | |
Honest summary: At comparable doses, Mounjaro has shown greater average efficacy. The new 7.2mg Wegovy narrows this gap significantly, but we don't yet have head-to-head data at that dose. Neither medication works equally for everyone.
Cost in 2026
This is where the picture shifted dramatically in September 2025, when Eli Lilly raised Mounjaro's UK wholesale price — a rise of roughly 170% from pre-increase levels. Almost every UK provider passed this on immediately.
As of April 2026, typical private prescription prices across GPhC-registered UK providers:
| Dose stage | Mounjaro | Wegovy |
|---|---|---|
| Starting dose | £149–£165/mo | £130–£149/mo |
| Mid titration | £199–£260/mo | £170–£229/mo |
| Standard maintenance | £300–£375/mo (15mg) | £249–£295/mo (2.4mg) |
| Higher maintenance | — | £295/mo (7.2mg) |
| Typical 12-month total | £3,050–£3,800 | £2,000–£2,700 |
Wegovy is now meaningfully cheaper at every dose stage for most providers. The gap is roughly £600–£1,100 over a full year of treatment at maintenance doses. This isn't trivial — especially given that both medications require indefinite use to maintain weight loss.
Prices vary significantly by provider. The ranges above are typical, but we've seen up to £100/month difference for the same dose between providers. Use the cleardose comparison tool to see current prices from all 42 UK providers ranked for your dose and situation.
Titration: how long to full dose
Both medications require gradual dose escalation — starting low and increasing over several months to allow your body to adjust. The titration schedules differ, and this matters for both timeline to full effect and cost during the ramp-up period.
Mounjaro has six dose increments versus Wegovy's five. This means it takes slightly longer to reach the full therapeutic dose, but many people find a dose that works well for them before reaching the maximum — and they stay there.
Notably: most people see meaningful results during titration, not just at full dose. Don't assume you need to reach 15mg Mounjaro or 2.4mg Wegovy to see significant weight loss.
Side effects
Both medications share a similar side effect profile — predominantly gastrointestinal, and most pronounced during dose increases as your body adjusts. The most common are nausea, diarrhoea, constipation, and reduced appetite (which is partly the point).
Because Mounjaro acts on two receptors simultaneously, there's a reasonable hypothesis that it could cause stronger GI effects. The clinical data doesn't strongly support this — discontinuation rates due to side effects are broadly similar across both medications, roughly 5–7% in trials.
What the data can't tell you is how you will respond. Some people find Wegovy causes significant nausea and switch to Mounjaro with much better tolerance — and some find the opposite. Individual GI response is genuinely unpredictable.
Report severe or persistent abdominal pain immediately. Contact your prescriber or call 111. Pancreatitis is a rare but serious potential side effect of both medications. Both are black triangle drugs — new or novel, subject to enhanced monitoring. Report side effects via the Yellow Card scheme.
Cardiovascular evidence
This is one area where Wegovy has a meaningful advantage that's often underplayed in comparison guides.
The SELECT trial demonstrated that Wegovy reduces major cardiovascular events — heart attacks, strokes, cardiovascular death — in people with established cardiovascular disease, even without significant weight loss. This cardiovascular benefit is now reflected in Wegovy's UK licence.
Mounjaro's cardiovascular outcomes data in the context of obesity (rather than diabetes) is still emerging. Early data is promising, but it isn't yet at the same level of established evidence as Wegovy's SELECT results.
For the majority of people taking these medications purely for weight loss, this distinction may not be clinically decisive. But if you have existing cardiovascular disease, it's a conversation worth having explicitly with your prescriber.
Who each is right for
- You want the highest average weight loss ceiling
- You haven't responded well to semaglutide-based treatments before
- You have type 2 diabetes alongside obesity
- Budget is less of a constraint
- Cost is a significant factor in long-term sustainability
- You have established cardiovascular disease
- You've previously tolerated semaglutide well (e.g. Ozempic)
- You want the new 7.2mg option for higher efficacy at lower cost than Mounjaro 15mg
The honest verdict
Mounjaro produces greater average weight loss and has a dual mechanism that works for more people. If efficacy is the primary criterion and cost is manageable, it's a reasonable first choice for most new patients.
But "most effective on average" doesn't mean "most effective for you." Individual response varies enormously, and the September 2025 price increase makes Mounjaro roughly £600–£1,100 more expensive per year. For a medication that requires indefinite use to maintain its effects, that's a meaningful sustainability question.
Wegovy's new 7.2mg dose narrows the efficacy gap considerably. And for people with cardiovascular risk factors, the SELECT trial data is a genuine clinical advantage.
The most important variable isn't which drug you choose — it's which provider you use. Price, included support, consultation quality, and switching flexibility vary enormously across the 42 UK providers. Two people on the same medication can pay £200/month more or less for identical outcomes.
See all 42 UK providers for your medication and dose, ranked for your situation — new patient, switcher, or looking for best long-term value.
Compare providers on cleardose* →