Mounjaro or Wegovy is now the most common question at our weight loss clinic — and unusually for medicine, there's a genuine head-to-head trial to answer it with. The short version: Mounjaro produces greater average weight loss, but 'better on average' isn't the same as 'better for you'. Here's the honest comparison — results, side effects, costs and the deciding factors — from The Vesey's GP-led clinic in Sutton Coldfield.
How They Differ
Both are weekly injections that mimic gut hormones regulating appetite. Wegovy (semaglutide) activates one receptor pathway — GLP-1. Mounjaro (tirzepatide) activates two — GLP-1 and GIP — which appears to amplify both weight loss and metabolic effects.
The numbers: in its pivotal trial Wegovy averaged around 15% body-weight loss at 68 weeks; Mounjaro reached up to 22.5% at the top dose at 72 weeks. The head-to-head SURMOUNT-5 trial confirmed it directly: roughly 20% loss with Mounjaro vs 14% with Wegovy over the same period. Both also improve blood pressure, lipids and blood sugar; semaglutide additionally has trial evidence of a 20% cut in major cardiovascular events in people with established heart disease — currently unique to it, and a genuine reason some patients with cardiac history choose Wegovy.
Dosing is stepped up gradually for both: Wegovy over ~16 weeks to 2.4mg weekly; Mounjaro through 2.5→15mg tiers as tolerated. Neither is a sprint; rushing titration is the main avoidable cause of side effects.
Side Effects and Tolerability
The profile is similar for both — nausea, constipation or diarrhoea, and reflux, concentrated around dose increases and settling for most people. In head-to-head data, tolerability was broadly comparable; some patients report Mounjaro slightly gentler at equivalent stages, but individual variation swamps the averages — plenty of people who struggle on one do fine on the other, and switching is a legitimate strategy rather than an admission of failure.
The serious-but-rare list is shared: gallstones (a risk of rapid weight loss by any method), pancreatitis, and dehydration; neither is used in pregnancy or with a history of medullary thyroid cancer. And the same two under-discussed issues apply to both — muscle loss without adequate protein and strength training, and rebound if stopped abruptly without a maintenance plan. The drug choice matters less than the programme around it.
UK Costs and Availability
Private UK pricing in 2026 is broadly similar per month: expect roughly £120–£250/month depending on drug and dose tier — Mounjaro's higher doses sit at the upper end, and prices have moved around as supply and list prices shifted. Availability of both is now generally good privately; NHS access remains tightly rationed.
At The Vesey, treatment starts with a GP assessment from £200 including baseline blood tests, medication is quoted transparently at assessment (no hidden dispensing markup), and monthly monitoring from £100 covers titration, side-effect management and progress reviews. Both drugs are prescribed; the recommendation is made on your history, not on stock levels.
Comparison shopping tip: quotes that undercut the market dramatically usually exclude monitoring entirely — the part that keeps treatment safe and effective. Compare the all-in monthly cost, not the vial price.
How We'd Choose — and How to Start
Lean Mounjaro if maximum weight loss is the priority and there's no specific reason otherwise — the head-to-head data is clear. Lean Wegovy if established cardiovascular disease makes its outcome data relevant, if you've tolerated semaglutide before, or if cost at your required dose tier favours it. Either way: the choice is individual, revisitable, and far less important than protein, strength training, sleep and an exit plan.
The Vesey's GP-led clinic covers all of it: assessment (from £200 incl. bloods), honest suitability advice — including when the answer is neither — titration, monitoring (from £100/month) and a structured maintenance plan. Same-week appointments, 7 days a week, Sutton Coldfield. Book online or call 0121 387 3727. Full background: our complete guide to weight loss injections.
The right drug is the one prescribed for you
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Frequently Asked Questions
Which gives more weight loss — Mounjaro or Wegovy?
Mounjaro, on the trial evidence: around 20% average body-weight loss versus 14% for Wegovy in the direct head-to-head SURMOUNT-5 trial. Individual responses vary widely, and Wegovy retains unique cardiovascular-outcome evidence relevant to people with established heart disease.
Can I switch from Wegovy to Mounjaro (or back)?
Yes — switching is common and clinically straightforward when supervised: the new drug is started at an appropriate tier rather than the top dose, with monitoring through the transition. Reasons to switch include plateaued results, tolerability or cost. Don't self-switch between online pharmacies without clinical oversight.
Are Mounjaro and Wegovy side effects different?
Broadly similar: nausea, constipation/diarrhoea and reflux, mostly during dose increases. Head-to-head tolerability was comparable, and individual variation is large — struggling on one does not predict struggling on the other. Slow titration and dietary adjustments manage most symptoms.
How much do Mounjaro and Wegovy cost privately in the UK?
Typically £120–£250 per month for the medication depending on drug and dose tier, plus clinical monitoring. At The Vesey: assessment from £200 including baseline bloods, transparent medication pricing at assessment, and monthly GP monitoring from £100. Compare all-in costs — cheap quotes usually omit monitoring.