Mounjaro®
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Start journey Learn moreWhat the evidence and your options actually tell you about switching
What the trial data says about tirzepatide after semaglutide
The most relevant head-to-head evidence comes from SURMOUNT-5, published in the New England Journal of Medicine in 2025. Over 72 weeks, adults with obesity who received tirzepatide lost significantly more body weight on average than those on semaglutide 2.4mg, the trial wasn't designed around patients switching mid-treatment, but it does establish that tirzepatide's dual-receptor mechanism produces a meaningfully different physiological response. A full comparison of the two medicines covers the mechanism and trial figures in detail.
SURMOUNT-1 (2,539 participants, 72 weeks) reported average weight reductions of around 20–21% at the 15mg dose of tirzepatide. STEP 1 reported around 15% for semaglutide 2.4mg. These are not directly comparable trials (populations, designs and run-ins differ) but NICE's appraisal of tirzepatide (TA1026) notes that indirect comparisons favour tirzepatide, and SURMOUNT-5 now provides direct evidence in that direction too. The practical implication: if your body has largely adapted to GLP-1 stimulation alone, adding GIP receptor activity through tirzepatide may produce a renewed response.
None of this means switching is automatic or right for everyone. Plateau on semaglutide can have causes that a new medicine won't fix, diet drift, a change in activity levels, an underlying condition that hasn't been addressed. A prescriber reviewing a switch needs to rule those out first. When switching is likely to be appropriate depends on how long you've been at maintenance dose and what your actual weight trajectory looks like.
How a plateau on semaglutide is different from semaglutide failing
Most people on semaglutide see the sharpest weight loss in the first few months, with the rate slowing as the body adjusts. That deceleration is normal, it is not the same as the medicine stopping work. A genuine plateau is typically defined as less than 5% weight loss after six months at the highest tolerated maintenance dose; NICE's appraisal of semaglutide for weight management (TA875) uses that threshold as one factor in assessing whether to continue.
Before any switch, it's worth reviewing: are you still at the recommended maintenance dose, or did titration stop early due to side effects? Has your diet changed? Are you getting adequate protein? These aren't trivial questions. Switching medicines carries its own adjustment period and its own side-effect profile. Tirzepatide's gastrointestinal effects (nausea, diarrhoea, constipation) follow a similar pattern to semaglutide's, typically most noticeable after starting or a dose change, then settling. You don't escape that adjustment just by changing the pen.
If the plateau is real and sustained, the dual-agonist mechanism of tirzepatide gives it a plausible pharmacological advantage. That's the conversation to have with a prescriber who can see your full picture. The timing and process involved in switching matters practically too, there are washout considerations and a starting-dose protocol to follow.
A side-by-side look at what differs between the two medicines
| Factor | Semaglutide (Wegovy injection) | Tirzepatide (Mounjaro) |
|---|---|---|
| Receptor action | GLP-1 only | GIP + GLP-1 (dual agonist) |
| Approx. average weight loss (pivotal trial) | ~15% over 68 weeks (STEP 1) | ~20–21% over 72 weeks at 15mg (SURMOUNT-1) |
| UK licence (weight management) | BMI ≥30, or ≥27 with ≥1 condition | BMI ≥30, or ≥27 with ≥1 condition |
| Maintenance dose options | 2.4mg weekly (7.2mg pen now also approved) | Up to 15mg weekly, titrated by prescriber |
| Head-to-head (SURMOUNT-5, NEJM 2025) | Comparator arm | Greater average weight loss |
| Injection frequency | Once weekly | Once weekly |
Ozempic is also semaglutide, but it is licensed for type 2 diabetes (not weight management) and should not be sought for that purpose. The comparison above applies to Wegovy (the weight-management formulation). For a closer look at how costs compare across these two options, the pricing gap between Wegovy and Mounjaro has its own context worth understanding.
What switching actually involves, and how nume handles it
Switching from semaglutide to tirzepatide isn't a same-day admin task. Tirzepatide has its own starting-dose protocol, treatment begins at 2.5mg to allow your system to adjust, regardless of what dose of semaglutide you were on. The dosing schedule when switching is something our prescribers set based on your individual history, not a fixed template.
At nume, transfer patients provide evidence of their current treatment, and our prescribers review that alongside the clinical rationale before approving a switch. There are no automatic renewals here, every decision is made by a named clinician reviewing your case. Once approved and dispatched, your Mounjaro KwikPen arrives by tracked DPD delivery the next working day, in plain packaging, ready to refrigerate at home.
The question of whether a switch is right for you isn't one a comparison page can fully answer. It involves your weight history, your current health picture, and sometimes conditions that affect which medicine fits better. Whether you're clinically suitable to switch is exactly the kind of question our team works through with you. Which medicine suits you is a clinical decision our prescribers make with you, not one we make for you in advance.
If you'd like to have that conversation, speak to our prescribers through a free consultation.
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