Mysimba vs Wegovy: two different approaches to weight loss

Picture the situation: you've been told mysimba is 'the tablet option' and wegovy is 'the injection', is that the whole story?

That framing captures something real but misses a lot. Mysimba (naltrexone/bupropion) is indeed an oral tablet, taken twice daily, that acts on appetite-regulating centres in the brain (specifically the hypothalamus and the reward pathway) to reduce hunger and food cravings. It contains two existing medicines combined in a modified-release formulation. Wegovy, by contrast, is injectable semaglutide, a GLP-1 receptor agonist made by Novo Nordisk, given once a week as a subcutaneous injection. It mimics a gut hormone that slows gastric emptying, increases the feeling of fullness and dials down appetite signals.

Those aren't cosmetic differences. They mean different side-effect profiles, different contraindications, different interactions and different average results. Mysimba is specifically contraindicated in people with uncontrolled hypertension, seizure disorders, eating disorders, or those using opioid medicines, the naltrexone component blocks opioid receptors, which matters clinically. Wegovy's cautions centre on a history of pancreatitis, certain thyroid conditions and its GI side-effect profile. A prescriber works through all of this during assessment; the eligibility picture for one person can be quite different from another's even at the same BMI.

The Wegovy treatment overview covers the full licensed indication and titration pathway in more detail if you want the background before consulting.

The numbers: what clinical trials reported for each medicine

This table pulls together the headline trial evidence. Numbers are from published clinical data and NICE appraisal documents; they reflect average results in trial populations alongside lifestyle changes, not guarantees for any individual.

The gap in average weight loss is substantial. Wegovy's STEP 1 trial, published in the New England Journal of Medicine, reported approximately 15% average reduction over 68 weeks at 2.4 mg. Mysimba's COR trials reported roughly 5–6% on average. That doesn't make mysimba useless, for someone who cannot tolerate injections, or for whom semaglutide is contraindicated, the calculus between mysimba and semaglutide changes. But the numbers are what they are. If you want to understand more about how semaglutide and Wegovy relate to each other as treatment options, that detail matters when weighing up which route is right for you. A higher-dose semaglutide option also now exists: the MHRA approved a 7.2 mg Wegovy pen in April 2026, with trials reporting around 20.7% average loss at that dose.

For a broader look at how semaglutide compares with other options in its class, the Wegovy versus other GLP-1 medicines page covers the landscape.

Side effects, practicalities and what actually lands on your doorstep

Side effects shape whether someone stays on a medicine long enough to see results, so they belong in this comparison.

Mysimba's most common effects are nausea, constipation, headache and dizziness, particularly in the first few weeks of dose escalation. Blood pressure can rise, so monitoring is required. Because of the naltrexone component it cannot be used alongside opioid painkillers, a practical restriction that rules it out for a meaningful proportion of people.

Wegovy's side-effect profile is GI-led: nausea, diarrhoea, constipation, indigestion and fatigue, most pronounced after starting or after each dose increase, and typically settling within a couple of weeks for most people. The NHS semaglutide medicines page lists the full profile and the signs that warrant prompt medical attention, worth reading before you start.

On the practical side: if Wegovy is prescribed through nume, what turns up is a DPD parcel the next working day, no branding on the outside, tracked to your phone, containing the pre-filled Wegovy pen. Mysimba arrives as a blister pack of tablets. Neither is complicated to use, but the injection does require technique the first time; our prescribers and aftercare team are available seven days a week for exactly that kind of question. For a full comparison of the semaglutide injection options specifically, this overview of how Wegovy compares across its main alternatives unpacks the nuance.

NHS access, private routes and which decision is yours to make

NICE did not recommend mysimba for NHS use, which means it sits almost entirely in the private prescription space. Wegovy has a NICE recommendation (TA875) for use within specialist NHS weight management services, alongside multidisciplinary support, for a maximum of two years, but waiting lists are long and the eligibility criteria are strict. Most people who come to a private service like nume do so because they don't meet the current NHS criteria or can't wait.

On the private side, a legitimate prescription for either medicine requires clinical assessment by a qualified prescriber. Any seller offering these medicines without that step is operating outside UK law. The GPhC pharmacy register lets you verify any online pharmacy in seconds; it's the fastest check you can do before handing over personal and medical information.

nume prescribes Wegovy for eligible adults as part of its weight-loss programme. It does not currently dispense mysimba. If you're trying to decide between these two medicines, or want to understand how Wegovy and Ozempic compare as semaglutide options, the right starting point is a consultation, not a comparison article. Our prescribers review every application personally, the same day it arrives. To explore your options, see the weight-loss treatments page, or read more about the wider range of evidence-based approaches on our weight-loss overview.

Which medicine suits you is a clinical decision our prescribers make with you, never one a comparison table can make alone.