Mounjaro vs Wegovy in Milton Keynes

How each one works

Both medicines borrow from the same piece of human biology. After a meal the gut releases hormones, incretins, that tell the pancreas to release insulin and tell the brain that you have eaten. Both of these medicines imitate one of those hormones, GLP-1, and hold that signal for far longer than the body would on its own. In practice people describe feeling full sooner, staying full for longer, and thinking about food less.

Semaglutide, the active ingredient in Wegovy, imitates GLP-1 alone. Tirzepatide, the active ingredient in Mounjaro, imitates GLP-1 and a second gut hormone called GIP at the same time. That is the substantive difference between them: one target versus two. What it means for any individual person is not something this page can tell you, and the difference does not make one a stronger version of the other.

Neither is an appetite suppressant in the old sense, and neither works on willpower. They change the signal your body sends about hunger and fullness, which is why the food and activity side of it still has to be built alongside, and why stopping the medicine without having built that tends to be followed by the weight returning.

What is the same

More than most comparisons admit. Both are weekly injections given with a pen you use yourself, on the same day each week. Both start at a low dose that steps up gradually, and in both cases the step-up is where side effects cluster. Both are prescription only, neither is appropriate in pregnancy or while breastfeeding, and both work best alongside changes to how you eat and move rather than instead of them.

The four differences that actually change the decision

Most of the table is the two medicines agreeing with each other. Both are weekly injections, both start low and step up, both carry the same common side effects, and both need the same monthly supervision. Four rows are where a real decision gets made, and they are worth spelling out.

1. The contraceptive pill

This is the difference people are least likely to know about and the one most likely to matter. Tirzepatide can reduce how well an oral contraceptive is absorbed, and the advice is to use an additional method, a barrier method, for four weeks after starting treatment and for four weeks after every dose increase. Given the dose rises several times over the first months, that is a recurring arrangement rather than a one-off. There is no equivalent advice for semaglutide.

If you take the pill and do not want to manage that, it is a legitimate reason to prefer one over the other, and it is the kind of thing that gets missed entirely by an online form that never asks.

2. Planning a pregnancy

Neither medicine is used in pregnancy or while breastfeeding. They differ on how far ahead you need to stop: at least one month before trying to conceive for tirzepatide, at least two months for semaglutide. If you are thinking about starting a family in the next year, that difference is worth planning around, and it is worth raising at the assessment even if it feels early.

3. Missing a dose, and travelling with it

Both are weekly, and both have a grace period if the day slips: up to four days late for Mounjaro, up to five for Wegovy. Beyond that the dose is skipped rather than doubled up. If your week is unpredictable, the extra day is a small but real practical difference.

Storage is the other practical one. Both live in the fridge at 2 to 8°C. Mounjaro can be kept out of the fridge below 30°C for up to 30 days; Wegovy for up to 28 days at 15 to 30°C. For a fortnight away that is academic. For a longer trip, or a summer with no reliable fridge at the other end, it is not, and it is worth saying so at the assessment rather than working it out at the airport.

4. Whether you want an injection at all

Semaglutide is also available as a daily tablet, and we prescribe it. There is no tablet form of tirzepatide. If needles are the thing standing between you and treatment, that is not a small consideration, and it narrows the choice by itself. The tablet is taken every day rather than once a week, on an empty stomach with a small sip of water, and you wait before eating or taking anything else. Some people find a daily routine easier than a weekly injection, and some find the opposite.

Doses, and why both start low

Neither medicine is started at the dose it is intended to end at. Both begin at a low starting dose and step up in stages over a period of months, and the first weeks are explicitly about tolerance rather than results. Going up too quickly is the most common reason people feel unwell on these medicines, and it is avoidable.

The step up is not automatic. At each monthly review the prescriber looks at how you have tolerated the current dose, what has happened to your weight, and whether anything has changed in your health, and decides on that basis whether to increase, hold or stop. Plenty of people stay at an intermediate dose because it is working and they feel well on it, and there is nothing wrong with that.

Both are weekly injections, given under the skin of the stomach, thigh or upper arm with a fine needle in a pre-filled pen. Most people find the injection itself unremarkable after the first one. You are shown how to do it at the clinic rather than sent away with a leaflet, and the pens need to be kept in a fridge until you start using them, which is worth planning for if you travel.

Side effects, and what they have in common

The common side effects are the same for both and are mostly digestive: nausea, constipation or diarrhoea, indigestion, burping, and feeling full uncomfortably quickly. They are usually worst in the days after a dose increase and settle as the body adjusts. Eating smaller portions, stopping when full rather than finishing the plate, and going easy on very fatty or very rich food make a real difference to how the first weeks feel.

Less commonly, both can be associated with gallbladder problems and with pancreatitis. Severe, persistent abdominal pain, particularly pain that goes through to the back, is the symptom to take seriously and to seek help for the same day rather than waiting for your review.

Both also interact with how quickly the stomach empties, which can affect other medicines, and both need care where there is a history of thyroid or pancreatic disease. This is precisely the material the assessment exists to go through, and it is why neither medicine is supplied here on the basis of an online form.

Switching between them

Switching is a prescribing decision and not one to make yourself. The doses are not equivalent, and starting the second medicine at the level you reached on the first is how people end up genuinely unwell. A switch means restarting the ladder, usually at or near the bottom, and building back up with the same monthly checks.

That said, switching is normal and it is not a failure. People move between these medicines because side effects did not settle, because progress stalled at a dose they could tolerate, or because supply of one became difficult. Raise it at your review and it will be managed properly rather than improvised.

What neither of them does

Neither medicine is a course of treatment with an end date built in. Both work while they are being taken, and appetite generally returns when they stop. That is not a failure of the medicine, it is what it is: they change a signal rather than reset it permanently.

Neither replaces the rest of it either. Weight lost quickly is not all fat, and keeping muscle means eating enough protein and doing some resistance work while the appetite is quiet. The people who do best treat the medicine as the window in which the harder habits become possible, rather than as the thing that does the work.

And neither is suitable for everybody. A history of pancreatitis, certain thyroid conditions, some gallbladder problems and a number of common medicines all need checking first. Occasionally the honest answer at the assessment is that neither of these is right for you, and you should expect to be told that rather than sold the nearest alternative.

Cost, and what a month includes

Both are private prescriptions and neither is routinely available on the NHS for weight management outside specialist services. Prices differ between the two, and differ by dose within each of them, because the higher doses contain more medicine. Current prices for every dose of each treatment are listed on our weight loss clinic page, and the monthly review is part of the service rather than an added charge. What you pay for is the medicine, the assessment and the ongoing supervision together.

How the decision is actually made

At the assessment the prescriber looks at your medical history, everything else you take, what you have tried before and what happened, and any reason one medicine would be a worse fit than the other. Availability is sometimes a factor too, and being told that plainly is better than being kept waiting.

You are not committed to the first choice. The monthly review exists partly so that a treatment that is not working, or not being tolerated, can be changed rather than endured. If you also want to consider a daily tablet instead of an injection, both are prescribed here and the treatments page covers all of them.

Getting either one in Milton Keynes

Both medicines are prescription-only, and both require an in-person assessment at Kenmakos Medical. We do not run an online questionnaire that ends in a prescription. Height and weight are measured here, your history and current medicines are gone through, and if neither treatment is appropriate you will be told that rather than sold something.

The clinic is on Barton Road in Bletchley, off Queensway and a few minutes from Bletchley station, with free parking directly outside. Patients travel in from across the city, from Central Milton Keynes down Saxon Street, from Wolverton and Stony Stratford, and from Newport Pagnell and the villages beyond. Appointments run to 8pm on weekdays and on Saturdays, which matters more than it sounds when treatment means coming back once a month rather than once.