Mounjaro vs Ozempic vs Wegovy vs Saxenda: Which Is Best in Ireland?

Four medicines, four different legal positions

Most comparisons of weight-loss injections start with the wrong question. They ask which one is strongest. In Ireland, the more useful question is which one you are actually eligible to be prescribed — because Mounjaro, Ozempic, Wegovy and Saxenda do not all hold the same licence, and two of them are not licensed for weight loss at all in the way people assume.

That distinction matters more than the efficacy league table. A medicine that is not licensed for weight management cannot be prescribed for weight management as a matter of routine practice, however well it performs in a trial. So this guide sets out what each medicine is, what it is licensed for in Ireland, what the evidence shows, what it costs, and how a doctor actually chooses between them.

Mounjaro vs Ozempic vs Wegovy vs Saxenda at a glance

All four are prescription-only medicines and none is suitable for everyone. Each requires a medical assessment before it can be considered.

The licensing difference most comparisons get wrong

Ozempic is the name most people know, and it is the one most often misunderstood. In Ireland, Ozempic is licensed to improve blood sugar control in adults with type 2 diabetes. It is not licensed for weight management. Weight loss is a well-documented effect of the medicine, and that is precisely why it became famous, but a licence covers a specific indication and Ozempic’s does not include obesity.

Wegovy contains the same active ingredient as Ozempic — semaglutide — at doses licensed specifically for weight management, generally in adults with a BMI of 30 or above, or 27 or above alongside a weight-related health condition — our Wegovy Ireland page covers its price and availability in detail. So if you have read that “Ozempic is the weight-loss one”, the accurate version is that semaglutide is, and Wegovy is the brand carrying that licence.

Mounjaro sits in both camps: it holds a licence for type 2 diabetes and a European licence for weight management in adults meeting BMI criteria. Saxenda is licensed for weight management too, including in adolescents aged 12 and over, but it is the outlier on practicality — liraglutide has a much shorter duration of action, so Saxenda is a daily injection rather than a weekly one.

How they work — and why Mounjaro is mechanically different

Ozempic, Wegovy and Saxenda all imitate GLP-1, a hormone the gut releases after eating. GLP-1 slows how quickly the stomach empties, prompts the pancreas to release insulin when blood sugar rises, and acts on appetite centres in the brain. The practical effect is that food stays satisfying for longer and the background mental chatter about eating tends to quieten.

Mounjaro adds a second mechanism. Tirzepatide activates both the GLP-1 receptor and the GIP receptor, another gut hormone involved in insulin release and fat metabolism. This dual action is the leading explanation for why tirzepatide has produced larger average reductions than semaglutide in trials that compared them.

The difference between Saxenda and the rest is duration rather than mechanism. Liraglutide clears the body far faster than semaglutide or tirzepatide, which is why it must be injected every day. For many people that daily commitment is the deciding factor, independent of any efficacy question.

What the clinical trials actually showed

These are averages from controlled clinical trials, in which participants also received diet and activity support. They describe what happened across a study population over a fixed period — not what any individual should expect.

• Tirzepatide (Mounjaro) — in the SURMOUNT-1 trial, participants on the 15 mg dose lost an average of about 20.9% of body weight over 72 weeks.
• Semaglutide (Wegovy) — in the STEP 1 trial, participants on the 2.4 mg dose lost an average of about 14.9% over 68 weeks.
• Liraglutide (Saxenda) — in a head-to-head trial against semaglutide, liraglutide 3.0 mg produced an average reduction of roughly 7%, against roughly 17% for semaglutide over the same period.

The ordering is consistent across the evidence base: tirzepatide has tended to outperform semaglutide, and semaglutide has tended to outperform liraglutide. What the averages conceal is the spread. Within every one of these trials some participants lost a great deal more than the average and some lost very little, and no trial can tell you in advance which group you would fall into. Tolerability, adherence, dose escalation and what you do around the medication all move the result.

Dosing and titration

None of these medicines starts at its full dose. Each begins low and steps up gradually over months, which is how the gastrointestinal side effects are kept manageable. Mounjaro starts at 2.5 mg weekly and steps up through 5, 7.5, 10, 12.5 and 15 mg. Wegovy escalates over several months toward 2.4 mg weekly. Saxenda steps up over weeks toward 3.0 mg daily.

This titration schedule is the reason the higher doses cost more and the reason results build over months rather than weeks. It is also why moving up a dose too quickly tends to cause problems: the escalation exists to let the gut adapt. If you are curious about the practice of holding a lower dose deliberately, we cover the evidence and the risks in our guide to microdosing Mounjaro.

Did you know you can claim up to 75% back on your health insurance?See how the claim works →

Side effects and how they are managed

All four share a similar side-effect profile, and it is overwhelmingly gastrointestinal: nausea, constipation, diarrhoea, reflux and reduced appetite to the point of forgetting to eat. These are usually most noticeable in the first days after a dose increase and settle as the body adapts. Most people who stop early do so during a dose step-up rather than at the start.

There are also situations in which these medicines are not appropriate at all, including a personal or family history of medullary thyroid carcinoma, certain pancreatic conditions, and pregnancy or planned pregnancy. This is the substance of a proper medical assessment, and it is why an online form alone is not a safe substitute for a doctor reviewing your history. Our detailed breakdown of what to expect and how to manage it is in semaglutide side effects.

One consideration that applies across all four, and that gets far too little attention, is body composition. Rapid weight loss of any kind takes muscle as well as fat unless protein intake and resistance training are deliberately protected. That is a treatment-quality issue rather than a drug-choice issue — see how to protect lean mass on a GLP-1.

What they cost in Ireland — and what the State covers

This is where the four separate most sharply, and where most comparison articles stop short.

For type 2 diabetes, both Ozempic and Mounjaro are funded through the Long Term Illness scheme, so an eligible patient with diabetes does not carry the cost. For weight management, the picture is almost entirely different: Mounjaro and Wegovy are not reimbursed by the State. A health-economic assessment carried out for the HSE concluded that funding Mounjaro for public patients would not represent value for money at the current price, estimating a cost to the State of roughly €5,500 to €6,200 per patient per year.

The one exception is Saxenda, which is reimbursed for weight management under a restricted HSE Managed Access Protocol — but the criteria are narrow, requiring a BMI at or above 35 together with prediabetes and high cardiovascular risk. Most people seeking treatment for weight loss in Ireland will not meet them.

The practical consequence is that weight-loss treatment here is overwhelmingly private-pay, which makes the all-in monthly cost the number that matters — doctor, medication and delivery together, not a headline consultation fee with the pharmacy bill arriving separately. We keep a dose-by-dose comparison across Irish providers in our Mounjaro prices in Ireland guide, and the current state of public funding in will Mounjaro be free on the HSE?

Two routes can return part of the cost, and both are widely missed. Several Irish health insurance plans handle a doctor consultation for weight management like any other consultant visit, and qualifying medical expenses including prescribed medication attract standard-rate tax relief through Revenue’s MED1 process. Both need an itemised receipt separating the doctor’s fee from the medication. We set out what each insurer accepts in getting up to 75% back on weight-loss treatment.

How a doctor actually chooses

In practice the decision is a sequence of filters, and efficacy is not the first one.

1. Is treatment appropriate at all? BMI, weight-related conditions, medical history, current medicines and previous attempts. For some people the answer is no, or not yet.
2. Which licences apply to your situation? Type 2 diabetes opens different doors than weight management alone. This filter alone removes Ozempic from most weight-management conversations.
3. What are the contraindications? Personal and family history rule specific options in or out regardless of preference.
4. What can you realistically sustain? A weekly injection and a daily one are different commitments, and the best medicine is one that is still being taken in twelve months.
5. What can you access and afford at the maintenance dose? The starter dose is not the ongoing cost, and stopping abruptly for financial reasons tends to undo the progress.

Only after those filters does relative efficacy decide anything — and by then the field has usually narrowed to one or two options.

Which might suit whom

Broad patterns, not recommendations. Your own assessment governs.

• Mounjaro is the option most often discussed for weight management in Ireland, holding both licences and the strongest trial averages, on a weekly injection.
• Wegovy is semaglutide at weight-management doses, with the longest real-world track record for this specific use and a weekly injection.
• Saxenda is the only route to State-reimbursed weight-management treatment, though under narrow criteria, and is the only one licensed from age 12 — at the cost of a daily injection and lower average results.
• Ozempic belongs to type 2 diabetes care in Ireland. If your interest is weight management, the honest answer is that the relevant semaglutide conversation is about Wegovy.

Which is right for you?

The comparison tables are the easy part. The decision depends on your medical history, which licences apply to your circumstances, what you can tolerate, and what you can sustain at the maintenance dose — and that requires a doctor who has actually reviewed your details. Our Irish-registered doctors assess each case individually and will say plainly when treatment is not the right course.

Mounjaro vs Ozempic vs Wegovy vs Saxenda FAQs

What is the difference between Mounjaro, Ozempic, Wegovy and Saxenda?

They use three active ingredients. Mounjaro is tirzepatide, a dual GIP and GLP-1 agonist. Ozempic and Wegovy are both semaglutide, a GLP-1 agonist, licensed for different indications and doses. Saxenda is liraglutide, a GLP-1 agonist with a much shorter duration of action, which is why it is injected daily while the others are weekly.

Is Ozempic licensed for weight loss in Ireland?

No. In Ireland Ozempic is licensed to improve blood sugar control in adults with type 2 diabetes, not for weight management. Wegovy contains the same active ingredient, semaglutide, at doses licensed specifically for weight management.

Which is most effective for weight loss?

In clinical trials, tirzepatide produced the largest average reductions, followed by semaglutide, then liraglutide. Those are population averages over fixed study periods with diet and activity support, and individual responses varied widely within every trial. Which is appropriate for you is a medical decision, not a ranking.

Is Mounjaro better than Wegovy?

Mounjaro has produced larger average reductions in trials, but the better option is the one that suits your medical history, that you tolerate, and that you can sustain at the maintenance dose. Some people do better on semaglutide, and tolerability often decides more than the trial averages do.

Does the HSE cover any of them for weight loss?

Mounjaro and Wegovy are not reimbursed by the State for weight management. Saxenda is, but only under a restricted HSE Managed Access Protocol requiring a BMI of 35 or above together with prediabetes and high cardiovascular risk. Ozempic and Mounjaro are covered under the Long Term Illness scheme for type 2 diabetes, which is a separate matter.

Why is Saxenda a daily injection?

Liraglutide clears the body considerably faster than semaglutide or tirzepatide, so it has to be given every day to maintain its effect. Semaglutide and tirzepatide persist long enough for once-weekly dosing.

Can I switch between them?

Switching happens for tolerability, supply or cost reasons, but it is a clinical decision. Doses are not equivalent between medicines, so a switch involves restarting a titration schedule rather than converting one dose to another.

How do I know which is right for me?

Only a doctor can decide, after reviewing your health profile, history and goals. You can take Slimbr’s free eligibility quiz to start a medical assessment.