Semaglutide vs Saxenda: Two Weight-Loss Injections, One Clear Difference

The biggest misconception: 'they're basically the same injection'

The myth that circulates most often about this comparison is that semaglutide and liraglutide are the same drug at different doses. They are not. Both belong to the GLP-1 receptor agonist class and both slow gastric emptying while reducing appetite, but they are distinct molecules with different half-lives, dosing frequencies and trial results.

Liraglutide (Saxenda) has a half-life of roughly 13 hours, which is why it requires a daily injection to maintain therapeutic levels. Semaglutide's molecular design gives it a half-life of about a week, which is what makes a once-weekly injection possible. That distinction has real consequences for day-to-day life. Missing a daily dose is easy to do; a weekly schedule is easier for most people to build into a routine, whether that is a Monday-morning habit before the kettle boils or a note in the calendar.

The trial evidence reflects this divergence too. The SCALE trial of liraglutide 3mg reported an average weight loss of around 8% over 56 weeks. The STEP 1 trial of semaglutide 2.4mg, published in the New England Journal of Medicine, reported an average loss of around 15% over 68 weeks. If you want to understand how the branded semaglutide product fits into this picture, our page comparing semaglutide and Wegovy explains the relationship clearly. Head-to-head data is limited, but the difference in trial averages is large enough that NICE references it when appraising the medicines separately.

These are averages across trial populations. Individual results vary, and a prescriber will weigh the evidence alongside your own health picture.

What each medicine is actually licensed for in the UK

Both medicines are licensed for weight management in adults with a BMI of 30 or above, or a BMI of 27 or above alongside at least one weight-related condition such as high blood pressure, raised cholesterol or type 2 diabetes. That part of the picture is similar.

The differences lie in what else each medicine is authorised for. Semaglutide (as Wegovy) now holds additional UK authorisations: one covers reduction of major cardiovascular event risk in eligible adults, and (as of 3 July 2026) a conditional approval for a form of fatty liver disease known as MASH. Liraglutide (as Saxenda) does not hold these additional indications for weight-management patients. A different liraglutide brand, Victoza, is licensed for type 2 diabetes, just as Ozempic is a semaglutide brand licensed for diabetes rather than weight loss. The brand distinctions matter, the difference between semaglutide brands is worth understanding before you start any treatment.

Saxenda is manufactured by Novo Nordisk, as is Wegovy. NICE has appraised Wegovy (semaglutide) under technology appraisal TA875; Saxenda does not have a comparable NICE recommendation for routine NHS commissioning in England. That affects NHS availability significantly.

Side-effect profiles: more alike than different

Because both medicines act on GLP-1 receptors, the side-effect profiles overlap considerably. Nausea, loose stools, constipation, indigestion and fatigue are the most commonly reported effects with both, typically most noticeable when starting treatment or moving to a higher dose, and often settling within the first couple of weeks.

Injection-site reactions are possible with either. Both medicines carry a precautionary note regarding acute pancreatitis, the MHRA's Yellow Card scheme is the right place to report any unexpected reactions. Severe, persistent stomach pain that radiates toward the back warrants prompt medical attention with either drug.

For women using oral contraceptives, tirzepatide (Mounjaro) carries a specific guidance note about reduced pill absorption, but semaglutide and liraglutide do not carry the same warning. If contraception is relevant to your situation, raise it at consultation.

Neither Wegovy nor Saxenda is recommended during pregnancy, while breastfeeding, or for anyone trying to conceive. Both are unlicensed in under-18s. The NHS patient information for semaglutide at nhs.uk covers the full list of precautions in plain language and is worth reading before any consultation.

What is licensed for weight loss in the UK, and what nume prescribes

Two injectable medicines are currently licensed in the UK for weight management: Wegovy (semaglutide) and Mounjaro (tirzepatide). Saxenda (liraglutide) is also licensed, but it is not available through nume's pharmacy, this page exists to inform, not to route you toward it.

If you are trying to decide between the options that are available privately, the comparison between Saxenda and Wegovy covers more detail on the liraglutide side, and the broader weight-loss treatment overview sets out the landscape clearly. For a sense of what Wegovy costs privately, the Wegovy pricing page gives honest context without hidden surprises.

Mounjaro, a dual GIP and GLP-1 receptor agonist, is the other option, and if you want to understand how semaglutide fits into the wider GLP-1 category before deciding, the GLP-1 vs semaglutide page explains the distinction clearly.

Choosing between treatments is a clinical decision, not one a comparison table can make for you. Our prescribers work through that with you at consultation, taking your health history, current medicines, and what you're hoping to achieve into account. Speak to our prescribers to start that conversation: begin your free consultation here.