What mounjaro is used for: licensed indications and clinical evidence

What the trial data actually showed before regulators approved it for weight loss

NICE's appraisal of tirzepatide (TA1026) was informed by the SURMOUNT clinical programme, with SURMOUNT-1 as its cornerstone. That trial randomised 2,539 adults with obesity or overweight and at least one weight-related condition, but without type 2 diabetes, to either tirzepatide or placebo over 72 weeks. At the 15 mg maintenance dose, average body-weight reduction was in the region of 20–21%, compared with around 2–3% on placebo. The SURMOUNT-1 paper in the New England Journal of Medicine set out these figures in full, and they underpinned NICE's recommendation in December 2024.

The mechanism behind those numbers is genuinely distinct from earlier GLP-1 medicines. Tirzepatide binds to receptors for both glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide-1 (GLP-1). Those two gut hormones together slow gastric emptying, reduce appetite and improve blood-sugar regulation. The practical result is a stronger and more sustained reduction in energy intake than single-pathway agents tend to produce. If you want a closer look at what drives those effects specifically, this page on the active ingredients behind weight loss unpacks it in more detail.

A later head-to-head trial, SURMOUNT-5, compared tirzepatide directly with semaglutide 2.4 mg over 72 weeks and found greater average weight reduction with tirzepatide. That result informed the comparative sections of NICE TA1026's committee discussion and has been widely cited since.

Which conditions Mounjaro is actually licensed to treat

The two UK-licensed uses sit in separate clinical contexts, though the medicine is identical in both.

For weight management, the licence covers adults with a BMI of 30 kg/m² or above, or those with a BMI between 27 and 29.9 kg/m² who also have at least one weight-related condition. That second group might include people with high blood pressure, raised cholesterol, pre-diabetes, obstructive sleep apnoea or osteoarthritis, among others. Treatment is intended alongside a reduced-calorie diet and increased physical activity, not as a standalone fix. Lower BMI thresholds can apply for people from certain ethnic backgrounds under UK guidance, check your eligibility through a free consultation if you are unsure where you stand.

For type 2 diabetes, tirzepatide is licensed to improve blood-sugar control in adults, again alongside diet and exercise. The SURPASS trial programme covered this indication separately. It is worth being clear that the two licences are distinct: a prescriber treating someone for diabetes is working within different clinical parameters than one prescribing for weight management, even though the pen in the fridge is the same.

What Mounjaro is not licensed for in the UK: weight loss in people under 18, use during pregnancy or breastfeeding, or use by people currently trying to conceive. Those exclusions apply regardless of BMI.

The conditions that overlap with both licensed uses

Many people who meet the criteria for weight management also live with type 2 diabetes, and that is where the uses genuinely converge. NICE TA1026 specifically names type 2 diabetes as one of the qualifying weight-related conditions for the weight-management licence, so a person with obesity and type 2 diabetes may be eligible under either or both pathways. Their prescriber decides which clinical route applies and monitors accordingly.

This overlap matters practically. The dosing schedule (starting at 2.5 mg and titrating in stages) and the injection method are the same across both indications, but the monitoring targets and review criteria differ. Anyone switching from a diabetes treatment to a weight-management licence, or vice versa, should have that transition discussed explicitly with their clinical team. Our tirzepatide information page covers the molecule itself in more detail for those who want the pharmacological background.

There are also conditions that benefit indirectly from the weight loss tirzepatide produces without being named indications in their own right. Blood pressure, sleep apnoea severity and lipid profiles often improve as body weight falls. Those improvements are clinically meaningful but they are consequences of the licensed use, not uses in themselves.

What mounjaro is not used for, and why that line matters

A question our prescribers hear fairly often is whether Mounjaro can be used for cosmetic weight loss in people who are at a healthy weight. The MHRA has been direct on this: GLP-1 medicines are not assessed or approved for quick or cosmetic purposes, and prescribing outside the licensed indication is a serious clinical and regulatory matter. The MHRA's Yellow Card reporting scheme is where patients and clinicians can flag any concerns about how these medicines are being supplied or used.

It is also worth separating Mounjaro from drugs that share similar brand recognition but different licences. Ozempic is semaglutide, licensed for type 2 diabetes in the UK, not for weight loss. A comparison of tirzepatide's uses against other medicines in this class may help if you have seen those names used interchangeably online and want a clearer picture.

For people curious about the cost of private treatment, the context behind Eli Lilly's 2025 UK price changes explains how the market shifted and what that means for private prescriptions now. That context is worth having before making any decision, and if you're planning ahead around something like a holiday or a long bank-holiday weekend, it's useful to know that orders placed before 12pm on a working day can be reviewed and dispatched the same day, arriving the next working day by DPD.

A prescriber's job is to match a licensed indication to a patient's actual clinical picture. Separately, if long-term safety is on your mind, this page addressing whether Mounjaro causes cancer sets out what the current evidence and regulatory assessments actually say. If you want to find out whether Mounjaro is appropriate for your situation, check your eligibility through our free consultation.