Mounjaro, Wegovy and Ozempic compared

The comparison in one paragraph

Ozempic and Wegovy contain semaglutide, a GLP-1 receptor agonist, given once weekly by injection under the skin. Mounjaro contains tirzepatide, which acts on the GLP-1 receptor and also on the GIP receptor, and is likewise given once weekly. Saxenda contains liraglutide and is given once daily. For weight management in the European Union, Wegovy, Saxenda and Mounjaro hold that indication. Ozempic does not: it is licensed for type 2 diabetes.

That last point is the single most misunderstood fact in this area. Ozempic being widely discussed as a weight loss medicine does not make weight loss its licensed use, and prescribing it for that purpose is off-label. MEDINOW does not issue Ozempic for weight management.

What is actually in each pen

Semaglutide, in both Ozempic and Wegovy, is a GLP-1 receptor agonist. It mimics a gut hormone released after eating, slows gastric emptying, and acts on appetite regulation in the brain. The practical effect most people describe is feeling full sooner and thinking about food less.

Tirzepatide, in Mounjaro, is a dual agonist. It acts at the GLP-1 receptor and additionally at the GIP receptor, another incretin pathway. Whether that translates into a meaningful advantage for a given individual is a clinical question rather than a marketing one, and it depends on tolerance as much as on average trial results.

Liraglutide, in Saxenda, is the oldest of the group in weight management use and is a daily injection rather than a weekly one. Some people prefer a daily rhythm; most find a weekly injection easier to keep up with over months.

All of these are prescription-only medicines throughout the EU. Assessment, dosing and monitoring are the reason for that, not bureaucracy.

Licensed indication: the difference that decides everything

Marketing authorisations in the EU are granted for specific indications, and the European Medicines Agency publishes the product information for each one. Wegovy, Saxenda and Mounjaro carry an indication in weight management alongside diet and increased physical activity, with entry criteria based on body mass index and on weight-related conditions. Ozempic carries an indication in type 2 diabetes.

Why this matters to you rather than to a regulator: the licensed indication determines what the doctor is assessing you against, what the product information says about dosing, and what a pharmacist expects to see. It also determines what is defensible. A doctor who declines to issue Ozempic for weight loss is not being obstructive, he is declining to prescribe outside the authorised indication when licensed alternatives exist.

The HPRA, the Irish medicines regulator, and the EMA both publish the authorised product information. If you want the definitive statement of what a medicine is licensed for, that is where it lives, not on a comparison page.

How the dose is stepped up

None of these medicines starts at the maintenance dose. All of them use a stepped escalation, because gastrointestinal side effects are dose-related and settle better when the body is given time.

Wegovy escalates over several months towards a maintenance dose of 2.4 mg once weekly, with the schedule set out in the product information. Mounjaro starts at 2.5 mg once weekly and moves up in defined steps depending on tolerance and response. Saxenda is escalated dose by dose over the first weeks. Ozempic, in its diabetes indication, has its own escalation.

Two practical consequences follow. First, this is not treatment you assess after a fortnight. Second, if a step-up is not tolerated, the answer is usually to hold at the previous dose for longer rather than to abandon the medicine or to push through. Anyone offering to start you at a high dose to speed things up is doing you harm, not a favour.

Side effects most people notice

Gastrointestinal effects dominate: nausea, vomiting, diarrhoea, constipation, reflux, burping and abdominal discomfort. They are most common during escalation and often settle. Eating smaller portions, stopping at the first sign of fullness, and avoiding very fatty meals helps more than anything sold to counteract them.

More serious but much less common problems are listed in the product information and are worth knowing by name: acute pancreatitis, gallstones and gallbladder inflammation, dehydration and kidney injury secondary to persistent vomiting, and in people also taking insulin or a sulfonylurea, hypoglycaemia. Severe persistent abdominal pain, particularly radiating to the back and with vomiting, needs urgent medical assessment rather than a wait-and-see week.

Muscle mass and nutrition deserve a mention that marketing rarely gives them. Rapid loss of weight on reduced intake means reduced protein intake too. Resistance exercise and adequate protein are part of doing this properly, not optional extras.

Who should not take them

The product information for these medicines lists contraindications and cautions, and they are not decorative. The only contraindication it records is hypersensitivity to the active substance or to any of the excipients. Rodent studies found thyroid C-cell tumours, and the product information judges the relevance for humans to be low without ruling it out; caution applies where thyroid disease is already present. We do not prescribe this class where there is a personal or family history of medullary thyroid carcinoma or multiple endocrine neoplasia syndrome type 2, and that is our own decision rather than a licensing restriction. A history of pancreatitis calls for caution and usually a different approach. Severe gastrointestinal disease, including gastroparesis, is a problem because these medicines slow gastric emptying further.

Pregnancy and breastfeeding are exclusions. Effective contraception is expected during treatment, and treatment is stopped in advance of a planned pregnancy, with the interval set out in the product information for the specific product.

Diabetic retinopathy in people with type 2 diabetes needs specific attention, because rapid improvement in glucose control has been associated with a temporary worsening. Anyone on insulin or a sulfonylurea needs those doses reviewed by the prescriber managing their diabetes, not adjusted alone.

This is the part of the assessment where a request is most often declined, and declining is the medicine working as intended.

What it costs in Ireland

These are not cheap medicines and they are usually paid for privately when prescribed for weight management. The monthly cost varies by product and by dose step, so a single figure quoted on a web page is likely to be out of date. The pharmacy is the reliable source for the current retail price of a specific pen at a specific strength, and it is worth asking before you commit to starting.

Reimbursement is the second half of the answer. HSE community schemes, including the Drugs Payment Scheme, have their own rules about which products are covered and for which purpose, and treatment prescribed for weight management generally sits outside them. Do not plan a budget around a scheme applying until you have confirmed it with the HSE or with your pharmacy.

The honest planning assumption is a recurring monthly private cost for as long as treatment continues, plus the cost of whatever assessment and monitoring is arranged. Treating this as a one-off purchase is the most common financial mistake people make with this class.

Compounded and unlicensed semaglutide sold online

Vials of what is described as semaglutide, sold without a prescription and often with dosing instructions in units rather than milligrams, are the single most dangerous thing in this space. They are not authorised medicines, their contents are not verified, and dosing errors with an unlabelled vial and an insulin syringe can be very large.

The HPRA regularly warns about prescription-only medicines offered for sale outside the regulated supply chain, and detains such products at the border. An authorised medicine reaches you through a pharmacy, in the manufacturer's device, with the package leaflet in the box.

If a price looks impossible, the product is not the same product. That is the whole explanation.

How MEDINOW assesses a weight management request

MEDINOW is operated by MEDINOW Sp. z o.o. and assessments are carried out by lek. Damian Wojno, a doctor registered in Poland, PWZ no. 3211301. The model is a written medical questionnaire that the doctor reads and answers in his own time. There is no video consultation, no telephone appointment and no live chat.

The weight management assessment costs 29.90 euro. You complete the questionnaire with your height, weight, medical history, current medicines and any previous treatment in this class, and the doctor decides whether treatment is appropriate and, if so, which product and which starting step. Where a prescription is issued, it is a PDF built to the annex of Implementing Directive 2012/52/EU and sent by e-mail; you bring it to any pharmacy with photo identification.

The fee covers the medical assessment, not the issuing of a document. If the doctor declines on medical or legal grounds, the fee is refunded. If the doctor asks you for documentation, you have at least 7 days to provide it and we will remind you before the deadline; if the consultation cannot be completed, we refund the full amount. Ozempic is not issued for weight management, and no request for a starting dose above the product information schedule is accepted.