Is Wegovy Better Than Mounjaro? What the Evidence Actually Shows

How each medicine works — and why it matters for results

Wegovy contains semaglutide, a GLP-1 receptor agonist. It mimics a gut hormone that signals fullness, slows gastric emptying, and reduces appetite. Mounjaro contains tirzepatide, which activates two receptors (GLP-1 and GIP) making it the only dual-agonist weight-loss medicine currently licensed in the UK. Engaging both pathways appears to produce a stronger appetite-suppressing effect, and the trial data reflects that.

In the STEP 1 trial, semaglutide 2.4mg produced an average body-weight reduction of around 15% over 68 weeks. Tirzepatide, studied in the SURMOUNT-1 trial, reached an average of roughly 20–21% at the 15mg dose over 72 weeks, with some analyses showing higher figures still. When the two medicines were put directly against each other in the SURMOUNT-5 trial (published in the New England Journal of Medicine in 2025) tirzepatide produced greater average weight loss than semaglutide 2.4mg in adults with obesity and no diabetes. That is meaningful evidence, not marketing. It is also worth noting that Wegovy's newer 7.2mg dose, approved by the MHRA in early 2026, narrows the gap somewhat, with trials reporting around 20.7% average loss at that strength.

The comparison becomes more nuanced when individual tolerability enters the picture, which is why a side-by-side look at the practical differences between Mounjaro and Wegovy is worth reading alongside this page.

Who each medicine is licensed for in the UK

Both are licensed for adults, but the thresholds differ slightly in practice. The table below sets out the key parameters.

Both carry a Black Triangle (▼) designation, meaning they are subject to additional MHRA monitoring. NICE's appraisal of tirzepatide (TA1026) and the semaglutide appraisal (TA875) set the NHS eligibility criteria, though private prescribing follows the licensed indications directly.

Side effects: similar profiles, some differences worth knowing

Both medicines share a broadly GI-led side-effect profile, nausea, loose stools, constipation, indigestion, and fatigue are most common, particularly after starting or moving up a dose. For most people these settle within a week or two, though not for everyone. Injection-site reactions are possible with either.

There is one clinically relevant practical difference. Women taking oral contraceptives alongside Mounjaro are advised to add a non-oral contraceptive method (condoms, for instance) for the first four weeks of treatment and for four weeks after each dose increase, because tirzepatide can slow stomach emptying enough to reduce pill absorption. The same caution does not have equivalent evidence behind it for Wegovy. If you use HRT, NHS England also advises discussing whether a transdermal option makes more sense while on tirzepatide. These are the sorts of conversation a prescriber walks through with you; they are not reasons to avoid either medicine, just factors that affect which one fits your situation.

For anything urgent (severe stomach pain that spreads to your back, signs of a serious allergic reaction, or symptoms of pancreatitis) seek medical help straight away and report it via the MHRA Yellow Card scheme. You can read more about Wegovy's safety profile on the Wegovy treatment page.

The decision is clinical, here is how to make it

If you are reading this weighing up the two options, the honest answer is that tirzepatide's average results are stronger in the data, but averages describe populations, not individuals. Some people respond better to one than the other. Some have medical history that makes one less suitable. Some are already established on semaglutide and switching carries its own considerations, which is why our page covering whether Mounjaro is actually better than Wegovy for your situation is worth a read before making any decisions. Cost, too, plays a role for many people, and the broader question of what other options compare to Wegovy is one more people are asking.

What a prescriber does is take your full picture: BMI, any existing conditions, current medicines, your goals, and your preferences, including whether you would rather avoid injections entirely (Wegovy is now also available as a once-daily tablet, approved by the MHRA in June 2026, for those who prefer it). If you have come across this medicine under a different brand or generic name, our page explaining the alternative name for Wegovy can help clarify what you have been reading about. That conversation is the right place for this decision, not a comparison article. Our clinical team, led by a GPhC-registered Independent Prescriber, reviews every consultation personally and the same day. There is no algorithm making that call.

You can explore both treatment options and start your free consultation at our weight-loss treatments page. If you have questions before then, the FAQs cover a lot of ground, or you can get in touch with our team directly. You may also find it useful to read through how Wegovy compares to Ozempic, particularly if you are wondering whether the two semaglutide products are interchangeable for weight loss.