Is Wegovy Like Mounjaro? What They Share and Where They Differ

You've been told both names and you're not sure whether it matters

It's a question our prescribers hear often: someone has read about Wegovy, then heard about Mounjaro, and they want to know whether the difference is mostly branding or genuinely clinical. The honest answer is that it's genuinely clinical.

Both medicines slow digestion, reduce appetite and help people eat less without the same degree of hunger they'd experience through diet alone. Both are given as a weekly subcutaneous injection using a pre-filled pen, both are licensed for weight management in UK adults with a BMI of 30 or above (or 27 or above alongside a weight-related health condition), and both carry a Black Triangle designation from the MHRA, meaning they're under additional monitoring. The NHS page on tirzepatide and its semaglutide equivalent cover the shared side-effect profile in plain language.

But the receptor difference matters. Mounjaro targets both the GLP-1 and GIP receptors. Wegovy targets GLP-1 only. GIP is a second gut hormone involved in appetite regulation and metabolic signalling, and adding it to the mix appears to amplify the effect, something the head-to-head trial data bears out.

If you want to understand how Wegovy's mechanism compares to Mounjaro's in more detail, we've covered that separately. For now, the short version: same family, meaningfully different pharmacology.

What the evidence actually shows, side by side

The clearest comparison comes from SURMOUNT-5, a 72-week open-label trial published in the New England Journal of Medicine in 2025 that ran tirzepatide directly against semaglutide 2.4mg in 751 adults with obesity and no diabetes. Tirzepatide produced greater average weight reduction. The NICE technology appraisal for tirzepatide (TA1026) notes that indirect comparisons also favour tirzepatide over semaglutide for weight loss.

That said, Wegovy's results in its own trials were substantial. The STEP 1 trial showed around 15% average body-weight reduction at the 2.4mg maintenance dose over 68 weeks. More recently, the MHRA approved a 7.2mg semaglutide pen in April 2026, and trials at that higher dose reported average weight loss of around 20.7% over 72 weeks, which narrows the gap with tirzepatide's top-dose performance considerably.

A practical note on the table: trial results are population averages. Individual response varies considerably, and both medicines are taken alongside lifestyle changes, reduced-calorie diet and increased physical activity. Numbers in isolation don't predict what happens for any one person. Those interested in the detailed Wegovy vs Mounjaro breakdown will find a fuller analysis there.

Side effects, practicalities and what actually turns up at your door

The side-effect profile overlaps heavily. Both medicines produce GI symptoms as the body adjusts, nausea tends to be the most reported, alongside loose stools, constipation, reflux and fatigue. These effects are most pronounced when starting treatment or moving to a higher dose, and usually settle within the first week or two. Neither medicine is free of them, and anyone with a history of pancreatitis needs to discuss this carefully with a prescriber; the MHRA highlighted acute pancreatitis as a known but infrequent risk across GLP-1 medicines in a Drug Safety Update in January 2026.

On the practical side, both arrive as pre-filled injection pens stored in the fridge. Each pen contains four weekly doses. When your first order comes through nume (sorry, through a dispensing pharmacy like ours) it arrives in a plain cardboard box via DPD with tracking, refrigerated for transit. You'll know exactly when it's coming.

One difference worth raising with a prescriber: tirzepatide may reduce how well oral contraceptive pills are absorbed, particularly in the first four weeks of treatment and after each dose increase. Women using the pill should discuss adding a non-oral method during those windows. NHS guidance does not flag the same concern for semaglutide, though any hormonal considerations are worth covering at consultation. For a broader look at how these two medicines sit against each other, including cost context, that page goes further.

Which one is right for you, and how a prescriber decides

Neither medicine is universally the better choice. Someone who tried semaglutide and found the GI side effects difficult may not find tirzepatide easier; someone whose weight is in a range where the difference in average results matters less might do very well on either. Medical history, other medicines, whether oral contraception or HRT is relevant, and how a previous GLP-1 treatment went all feed into the decision.

Switching between the two is a question our prescribers see regularly. If you've been on Mounjaro and are wondering about moving, the Mounjaro to Wegovy page covers what that involves. The reverse (moving from Mounjaro to Wegovy) has its own considerations too, which a prescriber will walk through with you. Cost is often part of that conversation; the price difference between Mounjaro and Wegovy is real and worth understanding before you decide.

What we won't do is tell you one is objectively better. The trial data favours tirzepatide on average weight loss at the highest doses, but averages describe populations, not individuals. Which suits you is a clinical decision our prescribers make with you.