Home / Compare / Mounjaro vs Wegovy
Mounjaro vs Wegovy
Mounjaro (tirzepatide) · Wegovy (semaglutide)
The short answer
On the trial evidence, Mounjaro produces more weight loss. The two were compared directly, which is unusual and valuable, and tirzepatide came out ahead.
That is not the same as it being the right choice for you. Both are licensed in the UK for weight management, both are prescription only, and the thing that actually decides which one you end up on is usually eligibility, availability and what your body tolerates, not the trial average.
Everything below goes into the detail, with sources on each record.
01Side by side
| Mounjaro (tirzepatide) | Wegovy (semaglutide) | |
|---|---|---|
| UK status | MHRA licensed | MHRA licensed |
| Availability | Prescription only | Prescription only |
| Evidence base | Human RCT, phase 3 | Human RCT, phase 3 |
| Controlled drug | No | No |
| Drug class | Dual GIP and GLP-1 receptor agonist | GLP-1 receptor agonist |
02What is the same
- Both licensed in the UK for weight management. Not off-label, not grey market.
- Both weekly injections under the skin, self-administered.
- Both prescription only. Anything sold without a prescription is unlawful, whatever it claims to be.
- Both work by reducing appetite, not by burning fat or raising metabolic rate.
- Both stop working when you stop taking them. Weight regain is the expected pattern for both, and this is the single most important thing they have in common.
- Both carry the same class cautions: additional contraception alongside the pill, telling your anaesthetist before surgery, and the January 2026 MHRA pancreatitis alert.
03What actually differs
The mechanical difference is receptor count. Semaglutide activates one receptor, GLP-1. Tirzepatide activates two, GLP-1 and GIP, both of which are gut hormones involved in the response to eating.
That is the whole biological story, and it is why the coverage calling tirzepatide "stronger semaglutide" is wrong. It is not a bigger dose of the same thing. It acts on an additional system, which means a partly different effect and its own set of unknowns.
Tirzepatide is a black triangle medicine, meaning the MHRA has flagged it for additional safety monitoring while the picture is still being built. Semaglutide has been in UK use since 2018 and has a much longer real-world safety record.
That is not a reason to avoid tirzepatide. It is a reason to report side effects through the Yellow Card scheme if you are on it, because that reporting is how the picture gets built.
04What the evidence says
The head-to-head trial is SURMOUNT-5, and it is the reason this comparison can be answered at all. Most drug comparisons rely on lining up separate trials with different populations and designs, which is unreliable. This one put both drugs in the same trial.
Tirzepatide produced greater average weight reduction than semaglutide over 72 weeks, in the region of 20 per cent against roughly 14 per cent. The trial was funded by Eli Lilly, which makes tirzepatide.
Those are averages across a trial population. Individual responses vary enormously, and June 2026 research suggested roughly one in ten people carry gene variants that blunt the response to GLP-1 drugs. Some people lose more on semaglutide than others lose on tirzepatide.
A funder testing its own drug against a competitor's is normal in late-stage development and worth knowing. It is also a trial design that is hard to fudge: both drugs, same protocol, published result.
05Which suits whom
Nobody on a website can tell you which drug suits you, and anyone who does is selling something. What can be said is which factors actually come into it.
- Tolerability decides more than potency. Both cause gastrointestinal side effects. A drug you can take beats a stronger drug you stop after six weeks.
- Track record matters to some people. Semaglutide has years more UK use behind it. If that reassures you, that is a legitimate reason and worth saying out loud to your prescriber.
- Existing conditions change the calculation. Type 2 diabetes, kidney disease, cardiovascular history and previous pancreatitis all bear on the choice, and none of it can be worked out from a comparison page.
- What you can actually get. Which brings us to the real answer.
06Getting either in the UK
For most people in the UK this is the question that decides it, not the trial data.
On the NHS, tirzepatide prescribing for obesity moved into the GP contract in April 2026 through new QOF indicators, with phased rollout and strict eligibility criteria. Practice participation is optional, so meeting the criteria does not guarantee your surgery is prescribing it. Semaglutide for weight management runs through separate NICE criteria and local commissioning.
Privately, both are available through registered UK pharmacies against a valid prescription. Prices vary and this site does not publish them.
Practical upshot: ask your GP practice what it actually offers rather than deciding which drug you want first. And if a supply problem comes up, temporary shortage across this class has been common since 2022 and is not the same as a drug being withdrawn.
07The honest bottom line
Tirzepatide won the head-to-head on weight loss. If that were the only consideration, the answer would be simple.
It is not, because both drugs only work while you take them, both cause side effects a meaningful proportion of people cannot live with, and access in the UK depends on criteria and postcode rather than preference. The realistic version of this decision is a conversation with a prescriber about what you are eligible for and what you can tolerate, not a choice you make in advance from a table.
08Common questions
Is Mounjaro better than Wegovy?
For weight loss on average, the head-to-head SURMOUNT-5 trial favoured tirzepatide, around 20 per cent against roughly 14 per cent over 72 weeks. Better on average is not better for everyone, and tolerability and access decide most real cases.
Can I switch from Wegovy to Mounjaro?
That is a prescribing decision, not a shopping one. People do switch, usually because of side effects, availability or response. It needs to go through whoever prescribes for you, because the starting dose is not simply carried across.
Are they both available on the NHS?
Both can be, under different routes and both with strict criteria. Tirzepatide prescribing for obesity entered the GP contract in April 2026 with optional practice participation, so availability varies by area. Ask your practice what it actually offers.
Do you regain weight on both?
Yes. Both work by suppressing appetite while present, so appetite and usually weight return after stopping. NICE guidance covers deprescribing and post-treatment support for tirzepatide, which tells you the health service treats stopping as a clinical event needing a plan.
Full record
Tirzepatide
The other licensed drug in this space, and the first approved anywhere to act on two hormone receptors at once.
Full record
Semaglutide
A licensed prescription medicine, and one of the two GLP-1 drugs most people are actually talking about.
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