Switching from Mounjaro to Wegovy: which dose do you move to?

Tirzepatide and semaglutide are not interchangeable: what the trial data shows

Starting from the clinical evidence is the right place here, because it explains why a straightforward dose conversion does not exist. Tirzepatide (Mounjaro) activates two receptors (GIP and GLP-1) while semaglutide (Wegovy) acts on GLP-1 alone. That structural difference means the two medicines produce distinct pharmacological effects at different dose levels, so your body's experience of one does not reliably predict its response to the other.

In SURMOUNT-1, published in the New England Journal of Medicine, tirzepatide at 15 mg produced average weight loss of around 20–21% over 72 weeks in adults with obesity. The STEP 1 trial for semaglutide 2.4 mg showed around 15% average reduction over 68 weeks. The SURMOUNT-5 head-to-head trial, also published in 2025, reported greater average loss with tirzepatide than with semaglutide 2.4 mg directly. Those are population averages, individual responses vary considerably. More recently, Wegovy's licensed maximum moved to 7.2 mg, with trials reporting roughly 20.7% average loss, narrowing that gap further.

None of this produces a conversion factor. What it does tell you is that the medicines sit at meaningfully different dose ranges (milligrams of tirzepatide are not equivalent to milligrams of semaglutide), and a prescriber assessing your switch will use clinical judgement rather than arithmetic. Our Wegovy vs Mounjaro comparison covers the evidence in more depth if you want to revisit why you might be switching in the first place.

Why 'restart from the beginning' is usually the answer

The standard recommendation from prescribers is to begin Wegovy at 0.25 mg (its lowest dose) when switching from Mounjaro, regardless of your Mounjaro dose at the time of the switch. That might feel frustrating if you were established on, say, 10 mg or 15 mg of tirzepatide. The reasoning is grounded in safety: your gastrointestinal system has adapted to one medicine's mechanism, and semaglutide will likely feel different in ways that are difficult to predict in advance.

Starting low gives your body time to adjust and keeps side-effect risk manageable. Nausea, constipation, and stomach discomfort are among the most commonly reported effects at the start of treatment, the licensed dose-escalation schedules exist precisely to reduce these early effects. Attempting to jump to a mid-point dose on Wegovy because you tolerated a mid-point Mounjaro dose is not evidence-based practice and is not something a responsible prescriber would recommend without careful individual review.

There is also a practical gap to consider. The switch itself usually involves a period without either medicine while the previous one clears. The timing of that gap is a clinical call. For a closer look at the specific dosing context when someone has been on 7.5 mg of Mounjaro, our page on switching from 7.5 mg Mounjaro to Wegovy covers that scenario in detail. Similarly, if you have been on the higher end of the Mounjaro range, the page on switching from 10 mg Mounjaro is worth reading alongside this one.

How the doses compare on paper, and why the table only tells part of the story

It helps to see both dose ladders side by side. The comparison below shows the licensed UK escalation schedules for each medicine. It is factual information, not a conversion guide, the numbers are not equivalent.

Sources: eMC SmPCs for Mounjaro and Wegovy; MHRA approval of the 7.2 mg Wegovy pen, confirmed 14 April 2026. A quick check worth doing before you switch: look at the PIL (patient information leaflet) inside your current pen, it states the exact storage requirements and what to do if you miss a dose, details that become relevant during any transition period.

The dose ranges look very different on paper, and they are. A person finishing at 15 mg of Mounjaro would not begin Wegovy at 2.4 mg; they would start at 0.25 mg and move through each step as their prescriber advises. Our page on Mounjaro to Wegovy dose conversion explores the logic behind this in more detail. For context on what any switch means for your monthly costs, the price difference between Mounjaro and Wegovy is worth reviewing too.

What the clinical assessment covers when you request a switch

A switch between these two medicines is not a simple admin task. A prescriber will want to understand why you are switching (whether it is due to side effects, supply issues, cost, or clinical response) because that affects the recommendation. Someone switching because of persistent GI intolerance on Mounjaro needs a different conversation from someone switching because their current supply chain has changed.

At nume, every request to switch is reviewed by a GPhC-registered prescriber. They will look at your dose history, your response and any side effects you have reported, and your current health picture before confirming suitability. If the switch goes the other direction, our page on switching from Mounjaro to semaglutide covers the dosage considerations in that framing. A full dosage guide for the Mounjaro-to-Wegovy switch is also available if you want to read through the full clinical picture first.

Both Mounjaro and Wegovy are prescription-only medicines. Which suits you (or whether a switch makes clinical sense at all) is a decision a prescriber reaches with you, not one to make alone. To begin that conversation with our team, check your eligibility and start a free consultation.