Can You Switch From Mounjaro to Wegovy, or the Other Way Around?

How do Mounjaro and Wegovy actually differ from each other?

The most practical difference is how each medicine works at the receptor level. Wegovy (semaglutide) is a GLP-1 receptor agonist: it mimics one gut hormone involved in appetite regulation and slows gastric emptying. Mounjaro (tirzepatide) activates two receptors (GLP-1 and GIP) making it the only dual-agonist weight-loss medicine currently licensed in the UK. That additional pathway appears to explain the weight-loss gap seen in clinical trials.

In the SURMOUNT-1 trial, tirzepatide produced an average body-weight reduction of around 20 to 21% at the 15mg dose over 72 weeks, cited in the NEJM SURMOUNT-1 paper. Semaglutide 2.4mg produced around 15% average reduction in the STEP 1 trial at 68 weeks. The SURMOUNT-5 head-to-head trial (NEJM, 2025) confirmed greater average loss with tirzepatide in a direct comparison. The new 7.2mg Wegovy dose, approved by the MHRA in April 2026, narrowed that gap (trials reported around 20.7% average loss at 72 weeks) so the picture is shifting.

The titration schedules also differ. Mounjaro starts at 2.5mg and works through six possible strengths up to 15mg. Wegovy begins at 0.25mg and escalates to 2.4mg as standard, with 7.2mg now available as the maximum. Neither schedule should be adjusted without a prescriber's involvement. You can read a more detailed side-by-side breakdown on our Wegovy vs Mounjaro comparison page.

Why would someone want to go from Mounjaro to Wegovy, or vice versa?

There are several legitimate clinical reasons a prescriber might recommend switching, none of which are about one medicine being simply "better" in the abstract.

A person moving from Mounjaro to Wegovy might be doing so because of tolerability, some people find the GI side-effect profile of one medicine easier to manage than the other, though both share a broadly similar nausea-led pattern at the start of treatment or after a dose increase. Cost can also be a factor: as widely reported following Eli Lilly's UK list-price changes from 1 September 2025, higher Mounjaro doses now carry a higher list price, and some patients look at whether semaglutide represents better value at their current dose. Our page on why Wegovy is often priced differently covers the background to that question.

Going the other direction (from Wegovy to Mounjaro) is more common among people who have plateaued on semaglutide and want to try a dual-agonist approach, or among those for whom Wegovy was originally chosen based on availability and who now want to reassess. If you are wondering whether you can go straight from Mounjaro to Wegovy without a gap in treatment, the answer depends on your current dose and clinical history rather than a fixed rule. The question of whether you can go from Wegovy to Mounjaro is, clinically speaking, the same process in reverse: a prescriber reviews your history, current dose, response and reasons, then decides how to time the transition. There is no established wash-out period defined in UK guidance for switching between these two medicines; timing is a clinical judgement. Our switching guide goes deeper into how the handover works in practice.

What does the comparison look like in numbers?

Both medicines are prescription-only and require clinical assessment for every supply. NICE's appraisal of tirzepatide (TA1026) and the corresponding appraisal of semaglutide (TA875) set out the NHS eligibility criteria for each. Private eligibility is determined by the licensed indications and the prescriber's assessment of your individual situation.

How does a switch actually happen through a regulated prescriber?

If you are already on one of these medicines and considering a move to the other, the starting point is a clinical conversation, not a pharmacy substitution. A prescriber will want to know your current dose, how long you have been on it, what results you have seen, your reasons for wanting to change, and whether any contraindications or interactions are relevant. People sometimes also ask whether they can move from Mounjaro to Wegovy on their own initiative, and the short answer is that any such change still requires a prescriber's sign-off rather than being a decision you make unilaterally. It is also worth noting that mixing Mounjaro and Wegovy, by taking both at the same time, is not something a prescriber would recommend, as the two medicines work on overlapping receptors and combining them has no established safety or dosing basis. For Mounjaro specifically, women on oral contraceptives should be aware that absorption of the pill may be reduced during the first four weeks of treatment and for four weeks after each dose increase, so a switch that changes your dose trajectory can affect contraceptive reliability too. NHS England's guidance on weight-management injections covers this and other practical considerations.

At nume, every repeat order and every change to treatment is reviewed by a GPhC-registered prescriber before anything is dispensed. If you are transferring from another provider, our team reviews your treatment history as part of the process. There is no auto-renewal and no algorithm making the call. If you have questions about where you stand, our FAQs cover the most common transfer scenarios, and our support team is available seven days a week.

Which medicine suits you at this point in your treatment is a clinical decision our prescribers make with you, not one that can be settled by a comparison table alone.