Semaglutide, Liraglutide and Tirzepatide: Which Weight-Loss Medicine Is Which?

Picture this: you've just Googled three drug names and ended up more confused than when you started

That happens a lot. The names get tangled because they describe different levels of the same story, some are active ingredients, some are brand names, and some are licensed for diabetes rather than weight management even though they circulate on social media as weight-loss medicines. Before comparing results, it helps to be clear on what each substance actually is.

Tirzepatide is the active ingredient in Mounjaro. It works on two gut-hormone receptors simultaneously (GIP and GLP-1) making it the only dual-agonist weight-loss medicine currently licensed in the UK. Semaglutide is the active ingredient in Wegovy (the weight-loss injection and, since June 2026, the first oral GLP-1 weight-loss tablet licensed in the UK). It activates the GLP-1 receptor only. Both slow gastric emptying and reduce appetite, but via different receptor combinations. Liraglutide, sold as Saxenda for weight management or Victoza for type 2 diabetes, is also a GLP-1 agonist, injected daily rather than weekly. If you want a fuller side-by-side breakdown of how these three options compare, our guide to Mounjaro, Wegovy or Saxenda walks through the distinctions in detail.

One thing worth knowing: Ozempic is also semaglutide, but it is licensed for type 2 diabetes, not weight loss. The same goes for Rybelsus, which is oral semaglutide at diabetes doses. If you've read about those names in a weight-loss context, this page clarifies exactly where they sit.

What the trial data shows, and how honest the numbers need to be

Clinical trials measure average weight loss in carefully selected participants following a prescribed programme alongside lifestyle support. Real-world results vary. With that framing clearly in place, here is what the published evidence reports:

The SURMOUNT-5 head-to-head comparison is the most directly relevant piece of evidence if you're weighing tirzepatide against semaglutide, and our page on semaglutide or tirzepatide explains what that trial means for someone choosing between the two. The nuances of that comparison are worth reading in full before drawing firm conclusions.

Liraglutide (Saxenda) was not included in these head-to-head trials. Its older data shows more modest average results than either of the above at the doses studied, and its daily injection schedule is a practical consideration for many people.

Licensing, eligibility and what's actually available through a private clinic

UK licensing sets the floor for what can legally be prescribed for weight management. The NICE appraisal of tirzepatide (TA1026) recommends it for adults with a BMI of 35 or above plus at least one weight-related condition, with lower BMI thresholds for certain ethnic backgrounds. Semaglutide's NICE recommendation under TA875 covers a similar population but applies within specialist weight management services for a maximum of two years. Neither of those NHS criteria applies to private prescribing, where the licensed SmPC eligibility (broadly, BMI 30 or above, or 27 with a weight-related condition) guides the prescriber's decision.

Liraglutide is licensed for weight management in the UK under the Saxenda brand, but nume does not dispense it. If Saxenda appeared in your research, the clinical picture today is that tirzepatide and semaglutide have stronger evidence behind them and are the treatments our prescribers work with. You can explore both on the weight-loss treatment overview.

None of these medicines are suitable during pregnancy, while breastfeeding, or when trying to conceive. They are not licensed for anyone under 18. A prescriber will also consider your full medical history, current medications and any contraindications, the consultation exists precisely for that assessment. If you're curious about how our clinical team approaches that review, you can read about our prescribers here.

Side effects, practicalities and what changes by switching

All three medicines share a GLP-1 mechanism in common, so their side-effect profiles overlap. Nausea, loose stools, constipation, bloating and fatigue are the most frequently reported effects across the class, typically most noticeable in the first weeks or after a dose increase, and often settling as the body adjusts. The NHS patient information for tirzepatide covers the full list in plain language worth reading before you start either medicine.

There are practical differences too. Tirzepatide is a once-weekly injection using a pre-filled KwikPen. The Wegovy injection is also once-weekly. Saxenda requires a daily injection, which some people find harder to sustain. The Wegovy tablet (approved by the MHRA in June 2026 as the first oral GLP-1 weight-loss medicine in the UK) needs no injection at all, though it requires a precise morning routine (empty stomach, plain water only, 30 minutes before food or other medicines) to absorb properly.

If you've already tried one medicine and are wondering about switching, that's a common and legitimate question, and a good starting point is understanding whether tirzepatide is actually the same as semaglutide before deciding whether a change makes sense. Switching from semaglutide to tirzepatide is something our prescribers assess case by case, taking into account your current dose, how long you've been on treatment and how you've responded. Which medicine suits you is a clinical decision our prescribers make with you.