Mounjaro®
Starting from £179.99/mo
Start journey Learn moreHow Mounjaro and Wegovy differ in practice — mechanism, evidence and access
Step 1: Understanding what each medicine actually does
Both injections work by mimicking gut hormones that signal fullness and slow the rate at which food leaves your stomach. The key distinction is that Wegovy acts on a single receptor (GLP-1) while Mounjaro activates two: GLP-1 and GIP. That dual action is partly why tirzepatide's trial results sit higher on average, though individual responses vary considerably. Wegovy's mechanism and dosing schedule are covered in full if you want the detail on how semaglutide works alone.
Wegovy's standard maintenance dose is 2.4mg weekly, reached by stepping up from 0.25mg over roughly four months. Mounjaro starts at 2.5mg (a tolerability dose whose job is to settle the digestive system rather than to drive weight loss) and can be titrated up to 15mg. In both cases the prescriber decides your pace, not a calendar. A closer look at the structural differences between the two medicines is available if you'd like to go deeper on the pharmacology.
Step 2: Reading the trial evidence side by side
The SURMOUNT-1 trial, published in the New England Journal of Medicine, randomised 2,539 adults without diabetes and reported average body-weight reductions of around 20–21% at the 15mg dose over 72 weeks. The STEP 1 trial for semaglutide 2.4mg, also in the NEJM, reported roughly 15% average loss over 68 weeks in a similar population.
A question our prescribers hear most weeks is whether those numbers mean Mounjaro will always outperform Wegovy for a given person. The honest answer is no. The figures are group averages: some participants on Wegovy lost more than the Mounjaro average, and vice versa. The SURMOUNT-5 head-to-head trial (2025) did find greater average loss with tirzepatide than with semaglutide 2.4mg, and if you want to understand how the Manjaro drug compares with Wegovy across the key trial findings, that page sets out what the evidence showed. Novo Nordisk also gained MHRA approval for a 7.2mg Wegovy dose in January 2026, with 72-week results of around 20.7%, narrowing the gap at the top end of Wegovy's range.
| Factor | Mounjaro (tirzepatide) | Wegovy (semaglutide) |
|---|---|---|
| Receptor target | Dual: GLP-1 and GIP | Single: GLP-1 |
| Average weight loss (pivotal trial) | ~20–21% at 15mg (SURMOUNT-1, 72 weeks) | ~15% at 2.4mg (STEP 1, 68 weeks) |
| UK maintenance dose range | Up to 15mg weekly | Up to 2.4mg weekly (7.2mg pen also approved) |
| NICE recommendation | TA1026: BMI ≥35 + ≥1 comorbidity (NHS) | TA875: BMI ≥35, specialist service, max 2 years (NHS) |
| Side-effect profile | GI-led: nausea, diarrhoea, constipation | GI-led: nausea, diarrhoea, constipation |
| UK licence holder | Eli Lilly | Novo Nordisk |
Trial figures are cited from the published NEJM papers; NICE recommendations from NICE TA1026 (tirzepatide) and NICE TA875 (semaglutide).
Step 3: Checking which one you might actually qualify for, and through which route
Both medicines share the same private licensed eligibility floor: adults with a BMI of 30 or above, or 27 or above alongside a weight-related condition such as type 2 diabetes, hypertension, high cholesterol or obstructive sleep apnoea. BMI alone never settles the matter; the prescriber weighs your full medical picture. Lower BMI thresholds apply for some ethnic backgrounds under UK guidance, which your prescriber will factor in.
On the NHS the picture differs. NICE's recommendation for tirzepatide (TA1026) applies within specialist services for adults with a BMI of 35 or above plus at least one comorbidity. Semaglutide under TA875 carries an additional condition: treatment must be delivered within a specialist weight management service and is approved for a maximum of two years. NHS availability for both is phased and varies by area, which is why many people explore the private route through a regulated pharmacy rather than joining a waiting list.
If you've been reading about semaglutide under its diabetes brand name, it's worth knowing that Ozempic and Wegovy contain the same active ingredient but carry different licences, Ozempic is licensed for type 2 diabetes, not weight management. That distinction matters clinically and legally. For a side-by-side specifically focused on whether Wegovy or Mounjaro suits a given situation better, that comparison is covered separately.
Neither Mounjaro nor Wegovy is the right choice in the abstract. Which suits you depends on your medical history, current medicines, lifestyle and what you and your prescriber decide together. At nume, our clinical team reviews every consultation personally. Start your free consultation at our treatment page and a prescriber will assess which option (if either) is appropriate for you.
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