Switching from Wegovy 2.4mg to Mounjaro: A Practical Guide

You're already on 2.4mg, does that mean you jump straight to a higher Mounjaro dose?

This is the question our prescribers hear most often from people transferring across. The short answer is no. Mounjaro starts at 2.5mg regardless of where you are on the Wegovy ladder, and that starting dose exists to let your system adjust to tirzepatide's mechanism, it isn't skipped just because you've tolerated semaglutide well for months. The two medicines act on different receptor combinations: semaglutide targets the GLP-1 receptor only, whereas tirzepatide activates both GLP-1 and GIP receptors. Tolerating one doesn't guarantee the same tolerability profile on the other, so the cautious titration pathway is there for good reason.

You can read more about how the dose conversion question is typically handled in our guide to dose conversion between Mounjaro and Wegovy, which covers the underlying pharmacology in more detail. For this direction of travel (Wegovy to Mounjaro) the practical starting point is always 2.5mg, titrating upward every four weeks as your prescriber advises, based on tolerability and response.

There is also a gap period to plan for. Semaglutide has a long half-life; most clinical guidance suggests leaving around a week after your last Wegovy dose before starting Mounjaro, though your prescriber will confirm the timing for your specific situation. Don't adjust this yourself.

What the evidence says about Mounjaro versus Wegovy 2.4mg

The SURMOUNT-5 trial published in the New England Journal of Medicine in 2025 directly compared tirzepatide against semaglutide 2.4mg in adults with obesity who did not have type 2 diabetes. Over 72 weeks, tirzepatide produced a greater average weight reduction. SURMOUNT-1 had already shown average body-weight reductions of around 20–21% at the 15mg tirzepatide dose, which NICE cited in its appraisal of tirzepatide (NICE TA1026, published December 2024). Wegovy 2.4mg's pivotal STEP 1 trial reported around 15% average weight loss over 68 weeks.

The comparison table below summarises the key factual differences between the two medicines at the doses most relevant to this switch.

Wegovy's 7.2mg dose, approved by the MHRA in April 2026 as a dedicated single-dose pen, narrows that average-result gap somewhat, with trials reporting around 20.7% weight loss) something worth factoring into the conversation if you haven't yet reached a plateau on the standard 2.4mg. The Wegovy vs Mounjaro comparison page covers that newer data in full.

Side effects: what changes and what stays the same when you switch

The side-effect profiles of the two medicines overlap considerably because both slow gastric emptying and reduce appetite through gut-hormone pathways. Nausea, constipation, diarrhoea, indigestion and fatigue are common to both, and they tend to be most noticeable in the early weeks of a new dose. Starting Mounjaro at 2.5mg means you're likely to experience a fresh wave of those GI effects, even if you've been symptom-free on Wegovy for months. That's normal and usually settles.

What's worth knowing: the MHRA issued a Drug Safety Update in January 2026 highlighting acute pancreatitis as a known but infrequent risk with GLP-1 medicines. Severe, persistent stomach pain that radiates toward the back is a reason to seek urgent medical attention, this applies to both medicines and doesn't disappear just because you've been on treatment before. If you have questions about which side effects to watch for after switching, our FAQs cover the most common concerns, and our prescribers are available for aftercare seven days a week.

The NHS patient information for tirzepatide at nhs.uk/medicines/tirzepatide is a reliable first reference for the full side-effect list and what to do about each one.

How to switch safely, and what a prescriber needs to know

You can't legally obtain Mounjaro without a prescription following clinical assessment. That assessment for a switch is more detailed than a first-time consultation: a prescriber needs to know your current dose, how long you've been on it, your weight trajectory, any side effects, and whether you're still responding. People transferring from another provider should be prepared to provide evidence of their current treatment.

At nume, every repeat order and every transfer is reviewed personally by a GPhC-registered Independent Prescriber before anything is dispensed. If you order before midday on a weekday, that review happens the same day, handy if you're trying to fit a medication admin task in before the school run. Our pharmacy's GPhC registration is publicly verifiable at the GPhC register (registration 9012878). You can also explore the full range of weight-loss treatment options if you're still weighing up the decision.

If you're curious about the reverse direction, we've written separately about switching from Mounjaro to Wegovy and what dose considerations apply there, including specific guidance for people who want to know about switching from 7.5mg Mounjaro to Wegovy or who are looking at switching from 10mg Mounjaro to Wegovy. The cost side of the equation is covered in our guide to whether Mounjaro or Wegovy is cheaper. Which medicine is right for you is a clinical decision made between you and a prescriber who knows your history, not one this page can make for you.