Wegovy vs Zepbound for Weight Loss: the UK Picture

What the head-to-head trial actually found

The most direct evidence comes from SURMOUNT-5, an open-label trial published in the New England Journal of Medicine in 2025. Over 72 weeks, 751 adults with obesity and no diabetes were randomised to either tirzepatide or semaglutide 2.4mg. Tirzepatide produced a greater average reduction in body weight than semaglutide at the doses compared. That is a meaningful finding (it is the clearest head-to-head data the field has) but it is worth reading carefully. The semaglutide arm used the 2.4mg maintenance dose. Since the trial was conducted, the MHRA approved a higher 7.2mg semaglutide dose (the dedicated single-dose Wegovy pen was approved on 14 April 2026), and early data suggest the gap narrows at that level.

SURMOUNT-1, the pivotal tirzepatide trial, reported an average body-weight reduction of around 20 to 21 percent at the 15mg dose over 72 weeks, in thousands of participants. The STEP 1 trial for semaglutide 2.4mg reported approximately 15 percent average reduction over 68 weeks. These figures come from different trials with different designs, so they are not a direct comparison — the question of which produces more weight loss is more nuanced than a single number suggests. Both figures should be framed as trial averages; individual results vary considerably.

One practical checking habit worth building: before any online provider quotes you results, look them up on the GPhC register at pharmacyregulation.org/registers, it takes under a minute and confirms whether the pharmacy is legally registered to dispense in the UK.

Zepbound in the UK: what the name actually means here

Zepbound does not exist as a UK product. Eli Lilly markets tirzepatide in the United States under the Zepbound brand for obesity; in the UK, the same medicine is sold as Mounjaro. The UK licensing, dosing presentations, supply chain and regulatory oversight are entirely separate from the US version. Any UK source claiming to sell or supply Zepbound should be treated with caution, it is not a product the MHRA has authorised here.

Mounjaro (tirzepatide) is licensed in the UK as a once-weekly subcutaneous injection, available in six strengths from 2.5mg up to 15mg, titrated by the prescriber. It is a dual GIP and GLP-1 receptor agonist (the only weight-loss medicine in the UK to act on both pathways simultaneously) and carries NICE approval for weight management under TA1026. If you are researching Zepbound because you want access to tirzepatide, comparing Wegovy and Mounjaro directly is the relevant question for UK readers. You can also read more about what switching between these treatments involves if you are already on one of them.

Wegovy (semaglutide) is a once-weekly injection, titrated from 0.25mg up to 2.4mg, or, since the April 2026 MHRA approval, up to the new 7.2mg single-dose pen for eligible patients. It acts on GLP-1 receptors only. NICE recommends it under TA875 within specialist weight management services for up to two years. Both medicines carry a Black Triangle designation, meaning they are subject to additional MHRA monitoring.

A side-by-side look at the key facts

Trial figures above are averages from cited studies; individual outcomes differ. Both Tier-1 and Tier-2 sources are used: NICE TA1026 (tirzepatide) and the STEP 1 trial published in the New England Journal of Medicine.

Which treatment can you actually access, and how?

For UK readers, the choice is between Wegovy and Mounjaro, both licensed, both available through a regulated private prescriber where you meet the clinical criteria. Neither is obtainable without a prescription following clinical assessment; any source offering them otherwise is operating outside UK law. The NHS England guidance on weight-management injections sets out the official access pathways clearly.

Private access through a GPhC-registered online pharmacy is the route for people who do not meet NHS thresholds or prefer not to wait. Our clinical team at nume (you can read about our lead prescriber's background) reviews every consultation personally before any prescription is issued. If you are weighing up the two medicines, our Wegovy versus Mounjaro comparison covers the clinical differences in more detail, including a closer look at how Zepbound and Wegovy stack up for those who have been researching the US literature, and our cost comparison page addresses the pricing picture honestly. You can also browse our treatment overview before deciding.

Which medicine suits your situation is a clinical decision. It depends on your health history, any existing conditions, what you have tried before, and how your body responds. Our prescribers work through that with you. If you are ready to start that conversation, begin your free consultation and a clinician will review it the same day.