30 September 2026
Wegovy vs Mounjaro in Ireland: Which Weight Loss Injection Is Right for You? (2026)
All medical information is reviewed by our clinical partners at MedicOnline.
Dr. Jahan Khan, CMO @ MedicOnline
IMC 409788
Both Wegovy and Mounjaro are now available in Ireland on private prescription. Both are clinically proven. Both work. So how do you decide which one is right for you? This evidence-based guide cuts through the noise.
If you have been researching weight loss injections in Ireland, you have almost certainly come across these two names. Wegovy (semaglutide) and Mounjaro (tirzepatide) are the two leading prescription GLP-1 medications available to Irish patients in 2026, and the question of which to choose is one of the most common we hear at Bua Health.
The honest answer is that there is no single "better" drug - the right choice depends on your individual health profile, medical history, and what your doctor recommends after assessment. What we can do is lay out exactly what the clinical evidence says, explain how the drugs differ mechanically, and help you understand who each one tends to suit best.
How Each Drug Works
Understanding the difference in mechanism is key to understanding why the two drugs perform differently in clinical trials.
Wegovy (semaglutide) is a GLP-1 receptor agonist. It mimics glucagon-like peptide-1, a naturally occurring gut hormone that signals fullness to the brain, slows gastric emptying, and reduces appetite.
Mounjaro (tirzepatide) is a dual GIP/GLP-1 receptor agonist. It activates both receptor pathways simultaneously. GIP receptor distribution differs from GLP-1, and combined activation appears to produce a greater average metabolic effect in direct trials.
In practical terms, both medicines produce substantial weight loss. In the one direct trial, Mounjaro beat Wegovy 2.4 mg[1]. Wegovy 7.2 mg has not been tested against Mounjaro, but in its own trial it reached a similar level to Mounjaro's top dose[2][3].
What the Clinical Trials Tell Us
The higher-strength Wegovy 7.2 mg dose has been approved in the EU and is now available in Ireland. In the STEP UP trial, people on Wegovy 7.2 mg lost 20.7% of their body weight on average over 72 weeks, and about one in three lost 25% or more[2]. Mounjaro 15 mg reached 22.5% in its own 72-week trial[3]. Results vary from person to person.
Side Effects: How Do They Compare?
Both medications share broadly similar side effect profiles, consistent with the GLP-1 class. Most common effects are gastrointestinal - nausea, constipation, diarrhoea, and stomach discomfort - particularly during dose escalation.
In the direct trial, stomach and bowel side effects led 5.6% of people on semaglutide and 2.7% of people on tirzepatide to stop treatment[1].
Both drugs are contraindicated in patients with personal or family history of medullary thyroid carcinoma (MTC) or MEN 2, and neither should be used during pregnancy.
Wegovy vs Mounjaro: Side by Side
Mechanism
Wegovy: GLP-1 receptor agonist
Mounjaro: Dual GIP/GLP-1 receptor agonist
Dosing
Wegovy: Once weekly; 0.25 mg to 7.2 mg maintenance
Mounjaro: Once weekly; 2.5 mg to 15 mg maintenance
Mean weight loss at top dose (separate trials, not directly comparable)
Wegovy: 20.7% at 7.2 mg (STEP UP, 72 weeks, taken as prescribed)
Mounjaro: 22.5% at 15 mg (SURMOUNT-1, 72 weeks, taken as prescribed)
Available in Ireland
Wegovy: Yes - private prescription
Mounjaro: Yes - private prescription
HSE reimbursement
Wegovy: Not yet (NCPE review ongoing)
Mounjaro: Not yet
Access and Cost in Ireland in 2026
Both Wegovy and Mounjaro are available in Ireland on private prescription. Neither is currently covered by the HSE or the Drugs Payment Scheme for weight management[5]. The NCPE has recommended that Mounjaro be considered for reimbursement if cost-effectiveness improves; the HSE decides[6].
Wegovy became formally available in Ireland in March 2025, and the higher-strength 7.2 mg single-dose pen became available in September 2026. Mounjaro is also available via private prescription from licensed Irish doctors for clinically eligible patients.
Following Eli Lilly's September 2025 price increase for Mounjaro, Wegovy is generally the more affordable option at standard maintenance doses. Prices vary by provider and dose level, so compare full costs including consultation fees.
Who Might Be Better Suited to Each?
This is ultimately a clinical decision for you and your doctor, but trial and real-world data suggest practical patterns:
- Wegovy may suit better if heart disease is a concern. Semaglutide is the only one of the two with a completed heart-outcome trial, and it carries a licensed indication for reducing cardiovascular risk[4].
- Mounjaro may suit better if you have already tolerated tirzepatide well and want to continue on it.
Individual response still varies. The right approach is to start, monitor, and adjust under medical supervision with your clinical team.
Ready to get started with Bua?
With Bua, you're supported by a specialist, doctor-led weight management service from day one. Here's how the process works:
Complete a secure online assessment with your medical history, goals, and weight-related health context.
Have your case reviewed by an IMC-registered doctor from our clinical partners at MedicOnline.
Agree a personalised treatment plan which may include Wegovy or Mounjaro, alongside ongoing clinical support.
Frequently Asked Questions
Related reading: Who qualifies for Wegovy in Ireland? and Who qualifies for Mounjaro in Ireland?.
References
- 1.Aronne LJ, et al. Tirzepatide as compared with semaglutide for the treatment of obesity (SURMOUNT-5). N Engl J Med 2025;393:26-36.Direct comparison over 72 weeks in 751 adults with obesity, or overweight with a weight-related condition, without diabetes. Open-label: participants and doctors knew which medicine was given. Each medicine was given at its highest tolerated dose: tirzepatide 15 mg (10 mg if not tolerated) or semaglutide 2.4 mg (1.7 mg if not tolerated). Weight change: 20.2% on tirzepatide, 13.7% on semaglutide (difference 6.5 points). Semaglutide 7.2 mg was not part of this trial.
- 2.Wharton S, et al. Once-weekly semaglutide 7.2 mg in adults with obesity (STEP UP). Lancet Diabetes Endocrinol 2025;13:949-963.Semaglutide 7.2 mg, 2.4 mg and placebo over 72 weeks in 1,407 adults with a BMI of 30 or more, without diabetes, alongside diet and exercise changes. Weight change when taken as prescribed: 20.7% on 7.2 mg, 17.5% on 2.4 mg, 2.4% on placebo. Across everyone in the trial, including those who stopped: 18.7%, 15.6% and 3.9%. Lost 25% or more of their body weight: 31.2% on 7.2 mg, 15.3% on 2.4 mg, 0% on placebo. The 2.4 mg group was small (201 people). As-prescribed and responder figures are from the Wegovy EU product information, section 5.1. STEP UP did not include tirzepatide; its figures cannot be compared directly with SURMOUNT-1 or SURMOUNT-5.
- 3.Jastreboff AM, et al. Tirzepatide once weekly for the treatment of obesity (SURMOUNT-1). N Engl J Med 2022;387:205-216.Tirzepatide 5 mg, 10 mg, 15 mg and placebo over 72 weeks in 2,539 adults with a BMI of 30 or more, or 27 or more with a weight-related condition, without diabetes, alongside diet and exercise changes. Weight change when taken as prescribed: 16.0%, 21.4% and 22.5%; placebo 2.4% (Mounjaro EU product information, section 5.1). Across everyone in the trial, including those who stopped: 15.0%, 19.5% and 20.9%; placebo 3.1%. SURMOUNT-1 did not include semaglutide; its figures cannot be compared directly with STEP UP.
- 4.Lincoff AM, et al. Semaglutide and cardiovascular outcomes in obesity without diabetes (SELECT). N Engl J Med 2023;389:2221-2232.Semaglutide 2.4 mg weekly against placebo in 17,604 adults aged 45 or older with existing cardiovascular disease and a BMI of 27 or more, without diabetes, followed for 39.8 months on average. Heart attack, stroke or death from a cardiovascular cause: 6.5% on semaglutide, 8.0% on placebo (hazard ratio 0.80, 95% CI 0.72 to 0.90). Tirzepatide has no equivalent published cardiovascular outcome trial yet.
- 5.Health Service Executive. Obesity: treatment: medicines.Which weight-management medicines the HSE covers under the medical card, Drugs Payment Scheme and Long-Term Illness Scheme. Last reviewed by the HSE on 5 December 2025.
- 6.National Centre for Pharmacoeconomics. Tirzepatide (Mounjaro) for weight management, HTA ID 24024. December 2025.The NCPE recommended that reimbursement be considered if cost-effectiveness can be improved relative to existing treatments. The HSE makes the decision.
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