Mounjaro and other medications: making sense of the choices

What sets Mounjaro apart from other licensed weight-loss medicines?

The question most people are really asking when they search this is: which medicine is likely to work best for me? That's a prescriber's call, but understanding the landscape helps you have a better conversation.

Mounjaro contains tirzepatide, a molecule that binds to two receptors simultaneously, GIP and GLP-1. Both are gut hormones involved in appetite regulation and blood-sugar control. Slowing gastric emptying and increasing feelings of fullness are effects common to this class, but the dual mechanism appears to amplify them. The SURMOUNT-1 trial, which enrolled 2,539 adults, reported an average body-weight reduction of around 20–21% at the 15mg dose over 72 weeks. You can read the full clinical basis in the NHS medicines page for tirzepatide.

Wegovy (semaglutide 2.4mg injection) targets the GLP-1 receptor only. It produced around 15% average weight loss in its pivotal 68-week STEP 1 trial. A higher 7.2mg Wegovy dose, approved by the MHRA in January 2026, closes some of that gap. Neither number guarantees what will happen for any individual. Both medicines require a reduced-calorie diet and increased physical activity to work effectively, and both are Black Triangle medicines under additional MHRA monitoring.

The full profile of Mounjaro covers mechanism, licensed strengths and storage in more detail if you want to go deeper before your consultation.

Medicines that come up in the search, and why the licensing matters

Ozempic is probably the name people encounter most often online, and that causes genuine confusion. It contains the same active ingredient as Wegovy (semaglutide) but it is licensed in the UK for type 2 diabetes management, not weight loss. Prescribing it off-label for weight management outside a clinical trial sits outside the licensed indications the MHRA has approved. The same applies to Rybelsus, which is oral semaglutide in 3mg, 7mg and 14mg tablets for diabetes.

Orlistat (sold as Xenical on prescription, or Alli as a pharmacy product at lower strength) works completely differently, it blocks the absorption of roughly a third of dietary fat in the gut rather than acting on appetite hormones. It is significantly older, with a well-understood side-effect profile that is largely gastrointestinal. NICE has not issued a technology appraisal for orlistat in the way it has for the newer injectable medicines.

For people considering tirzepatide and other medications together (such as their usual antidepressants, blood pressure medicines or contraceptive pill) interactions are a genuine consideration. The interactions page covers the evidence on what is and isn't affected by GLP-1 medicines. ADHD medication is one specific question that comes up regularly; the Mounjaro and ADHD medication page addresses that directly.

What the clinical evidence says about choosing between them

The SURMOUNT-5 trial (an open-label, head-to-head comparison of tirzepatide and semaglutide 2.4mg in 751 adults with obesity and without diabetes, published in the New England Journal of Medicine in 2025) is the most direct evidence available. Tirzepatide produced greater average weight reduction. NICE acknowledged in its appraisal of tirzepatide (TA1026, published December 2024) that indirect comparisons also favour tirzepatide, whilst noting that higher-dose semaglutide narrows the gap.

What trial averages don't capture is individual variation. Some people tolerate one medicine's side-effect profile better than the other's. Some have contraindications that rule out a particular agent. Some have already tried one and want to understand what switching would involve. None of these questions can be resolved by reading a league table, they need a proper clinical review.

At the GLP-1 medicines overview you'll find more on how the receptor pathways compare. For context on what private treatment typically costs across different medicines, the Mounjaro pricing page gives an honest picture of the market.

How suitability is decided in practice

Both Mounjaro and Wegovy are prescription-only medicines. The licensed eligibility criteria sit at BMI 30 or above, or 27 or above with at least one weight-related condition, things like hypertension, type 2 diabetes, obstructive sleep apnoea, dyslipidaemia or osteoarthritis. Lower BMI thresholds can apply for some ethnic backgrounds under UK guidance. But meeting those numbers is the start of the assessment, not the end of it.

A prescriber also looks at your medical history, current medications, previous weight-loss attempts, contraindications (including a history of pancreatitis or certain thyroid conditions), and whether the medicine fits your circumstances. Pregnancy, breastfeeding, or planning to conceive rules out both medicines. Under-18s are not licensed candidates.

The weight-loss medication and Mounjaro page goes into eligibility in more depth. If you want to explore how the broader range of weight-loss options fits together, that's a good place to look before a consultation.

Once a prescription is issued through nume, your treatment is dispatched the same day (for orders confirmed before 12pm, Monday to Friday) and arrives with DPD the next working day, tracked, in plain, unbranded packaging. The pen itself is a pre-filled KwikPen; each one contains four weekly doses. Speak to our prescribers to find out which medicine, if any, is suitable for you.