Mounjaro®
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Start journey Learn moreHow liraglutide and tirzepatide actually compare, mechanism, evidence and what the UK licence says
The biggest misconception: 'they're all just the same jab with a different label'
It's a reasonable assumption, several injectable weight-loss medicines exist, all involving a weekly pen, and the GI side effects overlap enough that people group them together. But liraglutide and tirzepatide are pharmacologically distinct in a way that genuinely matters to outcomes.
Liraglutide (the active ingredient in Saxenda, made by Novo Nordisk) is a GLP-1 receptor agonist. It mimics one gut hormone involved in appetite signalling and blood-sugar regulation, and it slows gastric emptying. That's the single-pathway approach shared by semaglutide (Wegovy/Ozempic) too, though liraglutide is a daily injection rather than weekly.
Tirzepatide (Mounjaro, made by Eli Lilly) is a dual GIP and GLP-1 receptor agonist, the only medicine of its kind currently licensed in the UK for weight management. It activates two separate receptor pathways simultaneously. The GIP component appears to amplify the appetite-reduction effect beyond what GLP-1 alone achieves, which is thought to be a significant reason for the larger average weight-loss figures seen in trials. You can read more about how that dual-receptor mechanism sets it apart in our GLP-1 vs tirzepatide explainer, and if you want to understand what the difference between Mounjaro and tirzepatide actually is, we cover that relationship in detail too.
So no, they're not the same jab with a different label. The receptor profile is fundamentally different, and the clinical outcomes reflect that.
What the trial evidence shows, side by side
Both medicines have robust clinical-trial programmes, but the numbers land in different places.
| Factor | Liraglutide (Saxenda) | Tirzepatide (Mounjaro) |
|---|---|---|
| Receptor targets | GLP-1 only | GLP-1 and GIP (dual agonist) |
| Injection frequency | Daily | Once weekly |
| Average weight loss in pivotal trial | ~5–8% body weight over ~56 weeks (SCALE trial, Novo Nordisk; varies by dose and population) | ~20–21% at 15mg over 72 weeks (SURMOUNT-1, NEJM) |
| UK licence for weight management | Yes (Saxenda) (BMI ≥30 or ≥27 with ≥1 weight-related condition | Yes (Mounjaro)) BMI ≥30 or ≥27 with ≥1 weight-related condition |
| NICE technology appraisal (weight loss) | No appraisal exists for liraglutide weight management | Yes, TA1026 (published Dec 2024, NICE TA1026) |
| Dispensed by nume for weight management | No | Yes |
The SURMOUNT-1 trial randomised 2,539 adults with obesity and found average body-weight reductions of around 20–21% at the 15mg dose over 72 weeks. No equivalent head-to-head trial of liraglutide directly against tirzepatide exists at the time of writing, so indirect comparisons should be treated as directional rather than definitive. NICE's committee, in appraising tirzepatide, noted that indirect comparisons favour tirzepatide over other GLP-1 medicines, but which medicine is appropriate for a given patient is still a clinical judgement, not a league table.
UK licensing, and why liraglutide's status matters here
Both medicines hold UK marketing authorisations for weight management, so both are legally available in the UK on a private prescription for eligible adults. The distinction is at the prescriber and pharmacy level: not every clinic or online pharmacy stocks every option, and licensing conditions differ in detail.
Liraglutide as Saxenda requires a daily injection, which some people find easier to fit into a routine; others prefer a once-weekly pen they can store in the fridge door and forget about until the same day each week. That's a practical consideration worth raising at consultation.
Tirzepatide has a NICE technology appraisal (TA1026) recommending it for NHS use under defined criteria, adults with a BMI of 35 or above and at least one weight-related comorbidity, with lower BMI thresholds for certain ethnic backgrounds. NICE TA1026 outlines the full criteria. No equivalent NICE appraisal exists for liraglutide in weight management. On the NHS, tirzepatide is being phased in through primary care; liraglutide's NHS landscape for weight management is different and more limited.
If you're weighing up newer agents too, our page on the difference between Mounjaro and retatrutide covers what's on the horizon beyond existing licensed medicines.
What nume prescribes, and what to do if you're considering liraglutide
Saxenda (liraglutide) is a legitimately licensed weight-management medicine, but it's not one our pharmacy currently dispenses. If a search has brought you here while comparing options, the medicines our prescribers can offer are Mounjaro (tirzepatide) and Wegovy (semaglutide), both licensed in the UK for weight management, both stocked in our GPhC-registered pharmacy (registration 9012878).
Our weight-loss treatment page sets out both options clearly. If you're curious about the broader injectable landscape before deciding, the tirzepatide vs liraglutide comparison page goes deeper on the clinical data, and our treatment overview explains how each medicine fits into a broader weight-management plan.
Which option suits you is a clinical decision our prescribers make with you, based on your BMI, your health history, your other medicines, and what you're actually trying to achieve. If you're also considering retatrutide and want to understand how reta and Mounjaro compare to one another, we explain the key distinctions on that page. The NHS guidance on weight-management injections is a useful reference for understanding the wider clinical context. Check your eligibility by starting a free consultation, a real prescriber, not an algorithm, reviews your answers the same day.
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