Is Mounjaro Semaglutide? What These Two Medicines Actually Share

The biggest mix-up: semaglutide and tirzepatide are not the same drug

Mounjaro's active ingredient is tirzepatide. Wegovy's is semaglutide. They are chemically distinct molecules made by different pharmaceutical companies, Eli Lilly makes Mounjaro, Novo Nordisk makes Wegovy. Both reduce appetite and slow how quickly food moves through your stomach, but they do this through different receptors. Semaglutide targets the GLP-1 receptor only. Tirzepatide targets both the GLP-1 and the GIP receptor simultaneously, making it the only dual-agonist weight-loss medicine licensed in the UK. That distinction matters clinically: the two pathways appear to produce a greater combined effect on appetite and blood-sugar regulation than either alone. So when someone asks whether Mounjaro contains semaglutide, the short answer is no, it contains a related but different compound. The confusion is understandable; both are injectable, both are once-weekly, and both emerged from the same broad class of gut-hormone medicines. The question of whether semaglutide and Mounjaro are the same comes up often enough that it has its own dedicated page.

Ozempic is also semaglutide, but it is licensed in the UK for type 2 diabetes, not weight management. Rybelsus is oral semaglutide, again for diabetes. Neither should be conflated with Wegovy in weight-loss contexts.

What the trial evidence shows, and where the comparison gets nuanced

Both medicines have large phase-3 trial programmes. SURMOUNT-1 (2,539 adults with obesity, 72 weeks) found tirzepatide produced average body-weight reductions of around 20–21% at the 15mg dose, as published in the New England Journal of Medicine. STEP 1, the equivalent semaglutide trial at 2.4mg over 68 weeks, found around 15% average reduction. A direct head-to-head, SURMOUNT-5, was published in the New England Journal of Medicine in 2025 and confirmed tirzepatide produced greater average weight loss than semaglutide 2.4mg in adults with obesity but without diabetes.

That said, the comparison is not entirely straightforward. Novo Nordisk's higher 7.2mg semaglutide dose, approved by the MHRA on 14 April 2026, has reported around 20.7% average weight loss over 72 weeks, narrowing the gap with tirzepatide 15mg considerably. And trial results are averages: individual responses vary, tolerability varies, and medical history shapes which medicine a prescriber would choose. If you are weighing up whether semaglutide or tirzepatide is the right option for you, the evidence side by side is covered in detail on that page. For a deeper look at the evidence side by side, this page weighs up semaglutide against Mounjaro on results.

UK licensing: what each medicine is actually approved for

In the UK, both tirzepatide (Mounjaro) and semaglutide (Wegovy) are licensed for weight management in adults with a BMI of 30 or above, or 27 or above alongside at least one weight-related condition such as high blood pressure, type 2 diabetes or obstructive sleep apnoea. Both carry a Black Triangle (▼), meaning the MHRA requires additional monitoring while post-marketing evidence builds. NICE's appraisal of tirzepatide (TA1026) and its separate appraisal of semaglutide (TA875) set different NHS access criteria: tirzepatide requires a BMI of 35 or above plus at least one weight-related comorbidity for NHS prescribing; semaglutide must be used within specialist weight management services for a maximum of two years.

Neither the NHS eligibility rules nor the licence criteria determine what a private prescriber concludes for an individual patient, that is a clinical assessment. For a fuller breakdown of how the two medicines compare on the question that really matters to most readers, this page examines which performs better and in what circumstances. Numeric BMI thresholds are a starting point; prescribers also consider your medical history, current medications and personal preferences. If you want to explore which is appropriate for you, check your eligibility with our prescribers, it's free, and the consultation is reviewed the same day.

The practical differences that matter day to day

Beyond the chemistry, tirzepatide and semaglutide differ in a few ways patients notice. Mounjaro is only available as an injectable pen; semaglutide now comes in an injectable form (Wegovy) and, since June 2026, as the first oral GLP-1 medicine licensed for weight loss in the UK, the Wegovy tablet. For anyone who finds injections uncomfortable, that option is worth knowing about. Both injectable forms are once-weekly; the oral tablet is once daily, taken before food on an empty stomach with a small amount of plain water.

Side-effect profiles overlap substantially, nausea, constipation, indigestion and fatigue are common to both, most noticeable at the start of treatment or after a dose increase, and typically mild-to-moderate. The NHS medicines page for tirzepatide covers Mounjaro's profile in detail. One prescribing consideration specific to Mounjaro: women taking the oral contraceptive pill should use an additional non-oral method of contraception during the first four weeks of treatment and for four weeks after each dose increase, because tirzepatide may reduce how well the pill is absorbed. There is no equivalent guidance for semaglutide. This is worth raising at consultation.

Which of these medicines suits you is a clinical decision our prescribers make with you, not a conclusion we'd draw from a comparison table alone. Readers sometimes arrive still uncertain about whether Mounjaro is a semaglutide drug, and that page explains the distinction clearly before any consultation. The two medicines are not interchangeable, and the right choice depends on your health history, your preferences and the clinical picture as a whole. Our clinical team at nume reviews every consultation personally.