Saxenda v Mounjaro: how these two weight-loss injections actually compare

You're weighing up daily injections against weekly ones — here's where the difference starts

Picture the situation: a friend tells you she's been using Saxenda for six months and has lost about half a stone. You've heard Mounjaro produces bigger results. You want to know whether the extra research backing is real, or just marketing noise.

The difference begins with biology. Saxenda contains liraglutide, a synthetic version of the gut hormone GLP-1 that signals fullness to the brain and slows gastric emptying. It has been licensed in the UK for weight management for several years and has a well-established safety record. The NHS patient information for tirzepatide sets out why Mounjaro's dual mechanism is considered distinct: tirzepatide also activates GIP receptors, a second gut-hormone pathway involved in appetite regulation and metabolic response. Activating both pathways appears to produce additive effects on weight reduction that a single-pathway medicine does not match.

There is also the practicality of daily versus weekly dosing. Saxenda requires an injection every day, titrated from 0.6mg up to 3mg over several weeks. Mounjaro's KwikPen is used once a week; each pen contains four doses and is kept in the fridge. For many people, a single injection on a Tuesday morning fits into a routine far more easily than a daily ritual, though individual preference matters, and a prescriber will factor your lifestyle into any recommendation.

The full explanation of whether Saxenda and Mounjaro are the same medicine covers the molecular differences in detail if you want to go deeper on the science.

The trial numbers are further apart than most comparison articles suggest

Clinical trial results for weight-loss medicines are often presented selectively, so it is useful to be specific. Saxenda's pivotal SCALE trials reported average body-weight reductions of roughly 5–8% over 56 weeks, meaningful, and statistically significant against placebo, but modest by the standards of newer medicines.

Mounjaro's results in SURMOUNT-1 (2,539 adults, 72 weeks, published in the New England Journal of Medicine) showed average weight reductions of around 20–21% at the 15mg maintenance dose. That is a substantially different order of magnitude. NICE's appraisal of tirzepatide (TA1026) reviewed this evidence and recommended Mounjaro for NHS use within defined eligibility criteria, noting the trial results in its committee discussion.

It matters how you read these numbers. Trial participants follow structured diet and activity programmes alongside medication, so real-world outcomes vary. Neither medicine is a standalone treatment: both are licensed alongside a reduced-calorie diet and increased physical activity. Still, the gap between 5–8% and 20–21% is large enough that the choice between Saxenda and Mounjaro is rarely a close call on evidence alone.

If cost context is part of your decision, the Mounjaro price comparison page covers what private treatment typically costs and what a legitimate price should include.

One practical note: Saxenda is not available through nume. Our prescribers work with Mounjaro and Wegovy, the two injections currently licensed for weight management in the UK with the strongest evidence base.

What is actually licensed for weight loss in the UK right now, and what that means for you

This matters because there is a common point of confusion: liraglutide is also sold as Victoza, which is licensed for type 2 diabetes. Saxenda and Victoza are the same molecule at different doses, and only Saxenda carries the weight-management licence. Similarly, semaglutide is available as Ozempic (diabetes) and Wegovy (weight management), the licence, not the molecule, is what determines lawful prescribing. Your prescriber will only issue a weight-management prescription for a medicine whose licence covers that indication.

The UK-licensed weight-loss injections available through regulated private pharmacies are Mounjaro and Wegovy. If you want to understand the relationship between tirzepatida e Mounjaro, including how the active ingredient and the branded medicine connect, that page sets it out clearly. Mounjaro (tirzepatide) starts at 2.5mg, with the prescriber titrating upward based on tolerance and response, and if you are looking at the starting stage of treatment specifically, the Mounjaro 2 page covers what to expect at the lower doses. Wegovy (semaglutide 2.4mg, with a higher 7.2mg dose now approved) follows a similar step-up schedule. Saxenda remains available through some services but is prescribed less frequently given the more limited weight-loss outcomes and the daily injection burden.

More detail on how tirzepatide works as a treatment is on the tirzepatide overview page, and a full picture of Mounjaro as a medicine is on the Mounjaro page. If you are curious whether your own situation fits the eligibility criteria, the weight-loss treatments overview explains who each medicine is licensed for.

A quick word on the process at nume: every consultation is read the same day by a GPhC-registered Independent Prescriber, not a triage algorithm. That clinical review covers your health history, current medicines and weight-related conditions before any treatment is considered.

Side effects and what Saxenda and Mounjaro have in common

Both medicines share a broadly similar side-effect profile because both act on GLP-1 receptors. Nausea, vomiting, diarrhoea, constipation and indigestion are the most reported effects with either, and they tend to be most noticeable in the early weeks of treatment or after a dose increase, then settle for most people. The NHS medicines information pages cover both in detail and are the right place to read the full lists.

There are some distinctions. Because Saxenda is injected daily, injection-site reactions may be more frequent simply by volume of injections. Mounjaro, given once weekly, produces the same class of GI effects but some users find the once-weekly rhythm easier to manage around daily life, the discomfort, where it occurs, tends to cluster around the day of injection rather than persisting every day.

Pancreatitis is a serious but uncommon risk with GLP-1 medicines generally. Severe stomach pain that spreads to the back, with or without vomiting, warrants urgent medical attention rather than waiting for a scheduled review. Report any suspected side effects using the MHRA Yellow Card scheme, which covers both prescription medicines and any suspect products you may have encountered online.

Questions our prescribers hear regularly can be explored on the nume FAQs page. If you have a specific concern, the team is reachable through the contact page seven days a week.

If Mounjaro sounds like the right direction after reading this, a free consultation with our prescribers is the first step, no referral, no waiting list.