Monjaro vs Wegovy: comparing two leading weight-loss injections

Imagine you're holding the two pens side by side, here's what's actually different inside them

Someone in your position might have already worked out that Monjaro and Wegovy aren't just different brands of the same thing. Monjaro contains tirzepatide, made by Eli Lilly, and it's a dual GIP and GLP-1 receptor agonist, the only weight-loss medicine in the UK that works on both pathways simultaneously. Wegovy contains semaglutide, made by Novo Nordisk, and acts on the GLP-1 receptor alone. Both slow gastric emptying, reduce appetite and help regulate blood sugar, but the dual-receptor action of tirzepatide produces a more pronounced effect on appetite hormones, which is reflected in the trial results.

In the SURMOUNT-1 trial, participants using tirzepatide at the highest dose lost an average of around 20–21% of their body weight over 72 weeks, as published in the New England Journal of Medicine. In the STEP 1 trial for semaglutide 2.4mg, the average was around 15% over 68 weeks. The SURMOUNT-5 head-to-head trial, also published in the New England Journal of Medicine in 2025, tested both medicines directly against each other in adults with obesity but without diabetes, and tirzepatide produced greater average weight loss. That's the most direct comparison available. Wegovy's newer 7.2mg dose, approved by the MHRA in January 2026 and now available as a single dedicated pen, narrows that gap somewhat, reporting around 20.7% average loss over 72 weeks.

Worth knowing: these are averages from thousands of participants. Individual results vary, and no medicine produces the same outcome for everyone. That's exactly why the prescriber assessment matters.

What the eligibility criteria look like for each, and where they diverge

The licensed eligibility thresholds are similar but not identical. For both injections, the private prescription route broadly requires adults with a BMI of 30 or above, or a BMI of 27 or above alongside at least one weight-related health condition such as high blood pressure, type 2 diabetes, high cholesterol or obstructive sleep apnoea. A lower BMI threshold can apply for some ethnic backgrounds under UK guidance.

On the NHS, NICE has appraised both medicines separately. Tirzepatide is recommended under NICE technology appraisal TA1026 for adults with a BMI of 35 or above plus at least one weight-related comorbidity, through a phased NHS rollout that began in June 2025. Semaglutide (Wegovy) is recommended under NICE TA875 for a maximum of two years, within a specialist weight management service, for adults meeting similar BMI thresholds. NHS waiting lists for Wegovy through specialist services remain lengthy in most areas.

For a private prescription, both medicines require clinical assessment, BMI alone doesn't determine the outcome. Our prescribers look at your full health picture, your medication history and any contraindications before making a recommendation. You can read more about how the two are assessed side by side on our page covering the key differences between Monjaro and Wegovy.

Side effects, injection schedule and what actually arrives at your door

Both injections share a broadly similar side-effect profile. The most common effects are gastrointestinal: nausea, loose stools, constipation, indigestion and fatigue. These tend to be most noticeable in the first few weeks or after a dose increase, then ease for most people. Both treatments begin at a low starter dose specifically to give your body time to adjust, with the prescriber guiding any increases through regular clinical review.

One practical difference: Monjaro comes as a KwikPen delivering four weekly doses per pen, while Wegovy is a pre-filled single-use pen. The injection sites are the same for both, abdomen, thigh or upper arm, rotated. Both require refrigerated storage; the exact room-temperature window for each is in the Patient Information Leaflet and should be followed precisely.

If you order through nume and your consultation is approved, your treatment arrives via DPD the next working day in a plain, unmarked box. The pen is packed with the clinical paperwork and our prescribers' contact details for aftercare. It's a small thing, but people notice it, the packaging tells your neighbours nothing.

For a closer look at how the Wegovy injection works as a standalone treatment, our Wegovy page covers its mechanism, schedule and eligibility in full. If cost is part of your thinking, our Wegovy price guide explains the private market honestly. And if you're curious about a different pairing, the Wegovy vs Ozempic comparison clarifies why Ozempic (though it contains semaglutide) is licensed for type 2 diabetes management, not weight loss.

The head-to-head numbers, side by side

These figures come from clinical trial populations and are averages; individual outcomes differ. Neither column constitutes a guarantee. Which medicine is more appropriate for a specific person is a clinical question, and our prescribers work through that with every patient. If you'd like to explore further before speaking to a clinician, the is Monjaro better than Wegovy page goes deeper on interpreting those numbers, and the what's better, Monjaro or Wegovy page addresses the question from a practical-decision angle. Our weight-loss treatment overview covers all the options available through nume. When you're ready, start your free consultation and a prescriber will talk through which approach fits your situation.