Mounjaro®
Starting from £179.99/mo
Start journey Learn moreHow the switch from 1.7mg Wegovy to Mounjaro actually unfolds
Step 1, understand what 1.7mg Wegovy represents in the titration
Wegovy's approved titration runs: 0.25mg, 0.5mg, 1.0mg, 1.7mg, and then 2.4mg as the standard maintenance dose. So 1.7mg is the penultimate rung, you're near the top of the schedule but not yet at the dose where most of the clinical trial weight-loss figures were measured. The STEP 1 trial, published in the New England Journal of Medicine, recorded an average reduction of around 15% body weight at the 2.4mg maintenance dose over 68 weeks, that benchmark was not reached at 1.7mg alone.
Why does this matter for switching? Because when a prescriber decides whether to move you to Mounjaro, they'll want to know whether 1.7mg has been your dose for long enough to assess its effect, or whether you simply haven't reached 2.4mg yet. That context shapes the conversation entirely. If tolerance has been the barrier, Mounjaro's starting dose of 2.5mg (a tolerability step, not a therapeutic one) may offer a gentler re-entry; if it's been a question of results, the prescriber will weigh the evidence for tirzepatide's additional mechanism.
The detail of how 1.7mg Wegovy compares to Mounjaro at equivalent stages is worth reading before your consultation. Knowing the landscape helps you ask sharper questions.
Step 2 (compare the two medicines on the facts that matter for a switch
Wegovy (semaglutide) activates a single receptor pathway) the GLP-1 receptor, to reduce appetite and slow gastric emptying. Mounjaro (tirzepatide) activates two: GLP-1 and GIP. That dual action is the core pharmacological difference, and it appears to translate into greater average weight reduction in head-to-head data. The SURMOUNT-5 trial, published in the New England Journal of Medicine in 2025, found tirzepatide produced greater average weight loss than semaglutide 2.4mg over 72 weeks in adults with obesity and without diabetes, a useful reference point when thinking about switching at the 1.7mg stage rather than after completing the semaglutide schedule.
| Feature | Wegovy 2.4mg (semaglutide) | Mounjaro up to 15mg (tirzepatide) |
|---|---|---|
| Receptor pathway | GLP-1 agonist | Dual GIP and GLP-1 agonist |
| Average weight loss (trial) | ~15% at 2.4mg, 68 weeks (STEP 1, NEJM) | ~20–21% at 15mg, 72 weeks (SURMOUNT-1, NEJM) |
| Approved UK maintenance dose | 2.4mg weekly (7.2mg also approved, Apr 2026) | Up to 15mg weekly |
| Starting dose | 0.25mg weekly | 2.5mg weekly |
| Injection frequency | Once weekly | Once weekly |
| Licensed in UK for weight management | Yes (NICE TA875) | Yes (NICE TA1026) |
These figures come from separate trials with different populations and durations; direct arithmetic comparison has limits. Understanding what 1.7mg Wegovy is equivalent to in Mounjaro requires a prescriber's assessment, not a conversion table.
Step 3, what the prescriber actually reviews before a switch
If you come to a consultation having been on 1.7mg Wegovy, the prescriber will look at several things: how long you've been at that dose, what weight change you've seen, any side effects that influenced your decision to switch, and your overall medical history. Evidence of your current treatment is needed, that's standard practice at a regulated service and it protects you.
Mounjaro starts at 2.5mg regardless of where you were on semaglutide. This is not a step backwards; the two schedules are independent and the titration exists to manage tolerability. Most people who have already tolerated semaglutide's GI side-effect profile find the early Mounjaro doses manageable, but that can't be assumed. Common side effects across both medicines are gastrointestinal in nature: nausea, loose stools, reduced appetite, and occasionally reflux or fatigue, typically most noticeable after a dose step and settling over days to a couple of weeks. The treatment overview covers side-effect management in more depth.
One thing patients often tell our prescribers: they wish they'd asked sooner whether switching was an option, rather than staying on a dose that wasn't working because they didn't know a different medicine existed. If that resonates, a consultation is a good use of 10 minutes. Our clinical team reviews every consultation personally.
Which medicine is right for you at this stage?
There is no single answer, and we won't pretend otherwise. Some people on 1.7mg Wegovy are progressing well and simply want to know what Mounjaro offers before their next review. Others have plateaued or are managing tolerability issues and are actively looking for a change. The clinical picture is different in each case. For a detailed look at the weight-equivalent question specifically, or at how dose conversion works in the other direction, those pages set out the pharmacological context.
What we can say with confidence, based on published evidence reviewed by our clinician-led team: tirzepatide has demonstrated greater average weight loss in head-to-head trials, and Wegovy at 2.4mg (or the newly approved 7.2mg) remains a well-evidenced option. Which suits your situation is a clinical decision our prescribers make with you, not for you. The NHS information on tirzepatide and on semaglutide gives a good grounding in both medicines before that conversation.
Looking to start your weight loss journey?
Take a quick eligibility quiz to explore your options and see how we can support you.