How liraglutide and semaglutide differ — and which is licensed for weight loss in the UK

Do they work in the same way?

Both drugs target the glucagon-like peptide-1 (GLP-1) receptor, the same gut-hormone pathway involved in appetite regulation, gastric emptying and blood-sugar control. Press on either drug and the broad description sounds identical: GLP-1 receptor agonist, slows stomach emptying, reduces hunger signals, once-daily or once-weekly injection.

The molecular difference is real, though. Liraglutide is a modified version of native GLP-1 with about 97% similarity to the human hormone, attached to a fatty-acid chain that extends its half-life to around 13 hours. That is long enough for once-daily dosing but not longer. Semaglutide is structurally further from native GLP-1, with a larger fatty-acid chain and albumin-binding properties that extend its half-life to roughly seven days, making a once-weekly injection viable. This structural gap explains why the two drugs sit in the same class yet behave quite differently in practice, as the NHS medicines information for semaglutide and the corresponding liraglutide pages both note.

Neither drug is a simple upgrade of the other; they are distinct molecules with distinct dosing schedules and distinct clinical track records. If you have read that one is "the same as" the other, that is an oversimplification worth setting aside before a prescriber discussion.

How different are the weight-loss results between the two?

If you have spent time comparing options online, you are probably aware that the numbers vary quite a bit, and that can be frustrating when you are trying to make a sensible decision.

The clearest published comparison comes from the STEP 1 trial, which evaluated semaglutide 2.4 mg over 68 weeks and found an average body-weight reduction of around 15% in adults with obesity and no diabetes, as reported in the New England Journal of Medicine. Liraglutide 3 mg (Saxenda) was studied in the SCALE Obesity and Prediabetes trial and produced average weight loss of around 8% over 56 weeks. These are not directly comparable trials (different populations, different timeframes, different design choices) but the direction of the evidence is consistent: semaglutide generally produces roughly twice the average weight loss of liraglutide at their respective licensed doses.

There is a third option now sitting above both of them. Tirzepatide (Mounjaro), a dual GIP and GLP-1 receptor agonist, produced average weight loss of around 20–21% at 15 mg in the SURMOUNT-1 trial. The semaglutide page on this site sets out the Wegovy trial evidence in more detail if you want to compare the numbers side by side. Results in clinical practice always vary by individual, and no medicine guarantees a specific outcome.

Which of the two is actually licensed for weight loss in the UK right now?

Both liraglutide (as Saxenda) and semaglutide (as Wegovy) hold UK licences for weight management in adults with a BMI of 30 or above, or 27 and above with at least one weight-related condition. Lower thresholds apply for some ethnic backgrounds under UK guidance. On paper, the licences look parallel.

In practice, the landscape has shifted. Saxenda has been subject to supply constraints and is not widely dispensed. Wegovy is the active choice for most regulated UK services, including the NHS pathway for specialist weight management. For context on how Wegovy pricing works privately, the Wegovy prices page explains what a transparent, all-included private prescription typically covers. NICE's recommendation for semaglutide (TA875) covers its use in specialist NHS weight-management settings; Mounjaro received its own NICE recommendation (TA1026) in December 2024 for a broader NHS rollout.

It is also worth being clear about the drugs that are NOT licensed for weight loss in the UK. Ozempic is semaglutide, but it is licensed for type 2 diabetes. Rybelsus is oral semaglutide, but again its licence is for diabetes, the weight-management oral semaglutide tablet is Wegovy (25 mg maintenance dose), approved by the MHRA in June 2026. The difference between Ozempic and Wegovy page covers that distinction if it is relevant to your search.

What is available from a regulated UK service, and what should you do next?

nume is a GPhC-registered pharmacy (registration number 9012878, verifiable at the GPhC register) that dispenses Wegovy (semaglutide) and Mounjaro (tirzepatide) for weight management. Liraglutide is not dispensed here. If you are weighing up semaglutide against other options, or if you have seen liraglutide discussed and wondered whether it is still the right track, a prescriber review is the most efficient way to get a clear answer, because eligibility, health history and any existing medications all feed into the decision.

You can also read more about how Saxenda compares with Wegovy if liraglutide is your starting point, or explore the different semaglutide products to understand which formulation maps to which licence. Our clinical team reviews every application personally, if you want a professional view on which licensed option suits your situation, the consultation is free and there is no obligation.

Speak to our prescribers by starting your free consultation at our treatment page.