Semaglutide versus liraglutide: comparing two GLP-1 medicines for weight loss

Step 1: understand what each medicine actually is, and what it isn't

Both semaglutide and liraglutide work by mimicking GLP-1, a gut hormone that signals fullness, slows gastric emptying, and reduces appetite. That shared mechanism is why they sit in the same drug class, but the similarities largely stop there.

Semaglutide is available as Wegovy (for weight management) and as Ozempic (for type 2 diabetes). The two brand names use the same active ingredient at different doses and under different licences. People searching for things like semaglutide versus Ozempic are often surprised to learn that Ozempic cannot legally be prescribed for weight loss in the UK, the distinction between Wegovy and Ozempic matters practically as well as legally. If you have been offered Ozempic for weight loss by a private provider, it is worth asking questions.

Liraglutide for weight management is sold as Saxenda (3 mg daily). Victoza is the same molecule at a lower daily dose, licensed for type 2 diabetes, the same Ozempic-style distinction applies. Saxenda's manufacturer is Novo Nordisk, which also makes Wegovy. Both Wegovy and Saxenda are licensed as weight-management medicines in the UK, but they are not the same treatment, and the question of which performs better has a fairly clear evidence-based answer.

Worth stating plainly: nume dispenses Wegovy for weight loss, not Saxenda. This comparison is here to help you understand your options, not to sell you one of them.

Step 2: look at the trial evidence side by side

The clinical trial data for the two medicines comes from separate programmes, so a direct head-to-head trial does not exist in the way the SURMOUNT-5 study compared tirzepatide with semaglutide. That said, the published results from the STEP and SCALE trial programmes give a clear indication of the gap.

The STEP 1 trial (68 weeks, semaglutide 2.4 mg weekly) reported an average body-weight reduction of around 15% in adults with obesity, published in the New England Journal of Medicine. The SCALE trials for liraglutide 3 mg reported average reductions of around 5–8% over 56 weeks, depending on the population studied. Both figures come from trials involving lifestyle support alongside the medicine, and both are averages, individual results vary.

The table below summarises the key factual differences.

The NICE appraisal of semaglutide (TA875) recommends it for NHS use within specialist weight management services, for a maximum of two years, with ethnic-background BMI thresholds 2.5 kg/m² lower than the headline figures. No equivalent NICE appraisal exists for liraglutide in weight management.

Step 3: consider the practical differences day to day

Practicality genuinely influences adherence, and adherence influences results. A once-weekly injection fits into most routines far more easily than a daily one. Plenty of people on liraglutide have described the daily injection as a source of fatigue, not physical fatigue, but the low-level effort of remembering and administering it every morning before breakfast.

Wegovy's storage requirement is the same as Saxenda's in principle: keep it in the fridge. In practice, the pen that comes out of the fridge door once a week is meaningfully less disruptive than one reached for every morning before the kettle has boiled. The full breakdown of practical differences between liraglutide and semaglutide covers things like titration schedules, side-effect timing and what to do if you miss a dose, decisions your prescriber and the Patient Information Leaflet should guide, not an article.

Side-effect profiles overlap significantly: nausea, vomiting, constipation and diarrhoea are the most common for both, and tend to be most noticeable after starting or after a dose increase, then ease for most people over the following weeks. If you are weighing up how liraglutide and semaglutide compare on tolerability and dosing, the NHS medicines pages for semaglutide give a patient-level overview of what to watch for and when to seek medical help.

Step 4: know what's actually available and where to go next

Wegovy is dispensed privately through regulated pharmacies like ours, and is also available on the NHS through specialist weight management services under TA875, though waiting times vary considerably. Saxenda is not dispensed by nume; if it interests you, your GP or a specialist service can advise.

Tirzepatide (Mounjaro) is a third option, a dual GIP and GLP-1 agonist that produces greater average weight loss than semaglutide 2.4 mg based on the SURMOUNT-5 head-to-head trial. It is also licensed in the UK for weight management. People sometimes ask how semaglutide and Wegovy relate to each other as treatment options, and our weight-loss treatment overview explains how the licensed options compare and what the consultation process covers.

If you are considering switching from liraglutide to semaglutide, that is a conversation to have with a prescriber rather than a decision to make based on availability alone. The right medicine depends on your medical history, current medicines, lifestyle and what you have already tried. Which suits you is a clinical decision our prescribers work through with you, start your free consultation to begin that conversation.