Mounjaro®
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Start journey Learn moreHow the switch actually works in practice: a step-by-step picture
Step 1, Understanding why 7.5mg Mounjaro does not map to a single Wegovy number
Mounjaro (tirzepatide) activates two gut-hormone receptors: GIP and GLP-1. Wegovy (semaglutide) targets only the GLP-1 receptor. Because the underlying pharmacology differs, you cannot line up the milligram scales and find a matching rung. A common misconception is that 7.5mg sits at roughly the midpoint of Mounjaro's range, so the equivalent Wegovy dose must be somewhere in the middle of its range too. That framing sounds logical, but it does not hold, and if you want to read through what a Wegovy equivalent to Mounjaro 7.5mg actually looks like in practice, that page sets out the reasoning in full. Effect on appetite, gastric emptying and weight loss is not proportional in the same way across the two molecules.
What clinical teams look at instead is where you are therapeutically: how much weight you have lost, which side effects you have experienced, and why you are considering a switch at all. A detailed breakdown of how doses compare across the two medicines is covered on the Mounjaro to Wegovy dose conversion page, which goes into the evidence behind each step. The short version for anyone on 7.5mg Mounjaro: Wegovy's maintenance dose is 2.4mg (or 7.2mg under the newer MHRA-approved schedule), but regardless of your starting point, Wegovy's titration always begins at 0.25mg, as set out in the prescribing guidance published on the electronic Medicines Compendium (eMC).
Step 2, What the trial data tells us about the two medicines side by side
The SURMOUNT-5 head-to-head trial, published in the New England Journal of Medicine in 2025, randomised adults with obesity and no diabetes to receive either tirzepatide or semaglutide 2.4mg for 72 weeks. Tirzepatide produced greater average weight reduction. In SURMOUNT-1, tirzepatide at its highest dose achieved around 20–21% average body-weight reduction. In the STEP 1 trial, semaglutide 2.4mg produced approximately 15% average reduction over 68 weeks, as published in the NEJM STEP 1 paper. The gap narrows with Wegovy's newer 7.2mg dose, which the MHRA approved in January 2026 and for which a dedicated single-dose pen was authorised on 14 April 2026; trials at 7.2mg reported around 20.7% average loss over 72 weeks.
The table below sets out the key factual comparisons. Numbers are from published clinical trials and regulatory documentation, they describe trial populations, not individual predictions.
| Feature | Mounjaro 7.5mg (tirzepatide) | Wegovy 2.4mg (semaglutide) |
|---|---|---|
| Mechanism | Dual GIP + GLP-1 receptor agonist | GLP-1 receptor agonist |
| UK licence (weight management) | BMI ≥30, or ≥27 with a weight-related condition | BMI ≥30, or ≥27 with a weight-related condition |
| Route | Once-weekly subcutaneous injection (KwikPen) | Once-weekly subcutaneous injection (pre-filled pen) |
| Average weight loss in trials (highest maintenance dose) | ~20–21% at 15mg (SURMOUNT-1, NEJM) | ~15% at 2.4mg (STEP 1, NEJM); ~20.7% at 7.2mg |
| Titration start (always) | 2.5mg | 0.25mg |
| NICE recommendation | TA1026 (Dec 2024, updated Sep 2025) | TA875 (Mar 2023) |
For a fuller comparison of Wegovy's available strengths alongside Mounjaro's, the Wegovy strengths vs Mounjaro page goes through each dose point in detail.
Step 3, What a prescriber considers before approving any switch
Switching between these medicines is not like swapping one antibiotic for another of the same class at the same strength. A prescriber will want to know why you are moving (whether it is availability, side-effect profile, cost, or a plateau in results) because the answer shapes the plan. Someone who has been doing well on 7.5mg Mounjaro but needs to switch for supply reasons is in a different clinical position from someone who found GI side effects difficult and wonders whether semaglutide suits them better.
Whichever reason applies, Wegovy's titration schedule must be followed from the starting dose. That is not a bureaucratic formality; starting at 0.25mg is how the medicine is designed to minimise nausea and allow your system to adjust. Jumping mid-schedule is not appropriate, and a prescriber will not approve it. If you are currently mid-treatment somewhere and want to understand the equivalent positions in Wegovy's range, the page on what Wegovy dose is equivalent to 7.5mg Mounjaro looks at this question specifically. The switching from 7.5mg Mounjaro to Wegovy guide covers the process in practical terms for transfer patients.
Both medicines are also Black Triangle (▼) products under additional MHRA monitoring. Neither is available without a prescription following clinical assessment, and NICE's recommendations for each (TA1026 for tirzepatide and TA875 for semaglutide) set out the population criteria. Which medicine suits you is a clinical decision our prescribers make with you, based on your full health picture.
Starting a consultation at nume
nume's consultation is free and takes a few minutes online. A GPhC-registered Independent Prescriber reads your responses and medical history the same day, not an automated system. For people transferring from another provider, evidence of current treatment is reviewed as part of the process. If you have questions before starting, our team is reachable via the contact page. You can also read about the clinical oversight behind the service on our prescriber's profile.
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