Retatrutide Ireland: what is it, can you get it, and how does it compare with Mounjaro, Wegovy and Ozempic?

Ireland-focused guide · reviewed 24 September 2026. Retatrutide is investigational and is not approved for public use. This article explains the evidence; it is not a route to obtain an unapproved medicine.

Retatrutide may be the most important obesity medicine that you cannot currently get from an Irish pharmacy.

The once-weekly injection being developed by Eli Lilly has produced some of the largest average weight reductions yet reported in late-stage drug trials for obesity.

That has created understandable interest in Ireland — and a lot of misleading information online.

The essential facts are:

• retatrutide is not approved in Ireland;
• it is not approved by the EMA, FDA or any other medicines regulator for public use;
• there is no legitimate Irish retail price for it;
• it remains an investigational medicine being studied in Phase 3 trials;
• separate trials suggest weight loss may be greater than that seen in pivotal trials of Wegovy and Mounjaro, but retatrutide has not yet beaten Mounjaro in a published head-to-head trial.

The study that could answer that last question directly — TRIUMPH-5, retatrutide versus tirzepatide — is already underway and is expected to complete in late 2026.

That makes this a medicine worth watching very closely.

Retatrutide Ireland: the short answer

Question	Answer as of September 2026
What is retatrutide?	An investigational once-weekly injection that activates GIP, GLP-1 and glucagon receptors
Is retatrutide a GLP-1?	It acts on GLP-1, but it is more accurately described as a triple hormone receptor agonist
Is it approved in Ireland?	No
Can a GP prescribe it in Ireland?	Not as an approved commercial medicine
Can you buy it from an Irish pharmacy?	No legitimate approved retail product exists
Can you buy “retatrutide” online?	Products sold outside authorised clinical trials are unapproved and may be illegal or unsafe
How much weight loss has it produced?	Up to 28.3% average weight loss at 80 weeks in Lilly’s TRIUMPH-1 efficacy analysis; 25.0% in the treatment-regimen analysis
Has that Phase 3 obesity result been peer-reviewed?	The main TRIUMPH-1 obesity results were company-reported topline data at the time of review; Phase 2 obesity and Phase 3 diabetes data are peer-reviewed
When will it be available in Ireland?	There is no confirmed Irish launch date

What is retatrutide?

Retatrutide is an experimental peptide medicine developed by Eli Lilly.

Its development code is LY3437943.

In clinical trials it is given as a once-weekly subcutaneous injection.

What makes it different from the best-known obesity medicines is the number of hormone receptors it targets.

Wegovy and Ozempic

Semaglutide activates the:

GLP-1 receptor

Mounjaro

Tirzepatide activates:

GIP + GLP-1 receptors

Retatrutide

Retatrutide activates:

GIP + GLP-1 + glucagon receptors

That third component — glucagon receptor agonism — is the main reason retatrutide is often described as a triple agonist.

Is retatrutide a “GLP-3”?

No.

You may see retatrutide called:

• “GLP-3”;
• “triple G”;
• “reta”.

“Triple G” is an informal nickname.

But GLP-3 is not a scientific drug class.

Lilly itself says the more accurate term is triple agonist, because the molecule activates three different receptors: GIP, GLP-1 and glucagon.

There is no third GLP hormone being targeted.

How does retatrutide work?

The simplest explanation is that it combines several metabolic signals in one molecule.

GLP-1

GLP-1 receptor activation can:

• reduce appetite;
• increase feelings of fullness;
• slow gastric emptying;
• increase glucose-dependent insulin secretion.

This is the pathway used by semaglutide medicines such as Wegovy and Ozempic.

GIP

GIP receptor activation is also involved in insulin secretion and energy metabolism.

Tirzepatide — Mounjaro — combines GIP and GLP-1 agonism.

Glucagon

Glucagon is more complicated.

It is often taught simply as the hormone that raises blood glucose.

But glucagon signalling also affects:

• liver metabolism;
• fat metabolism;
• energy expenditure.

The idea behind retatrutide is that combining glucagon receptor activity with GIP and GLP-1 activity may produce stronger effects on energy balance and body weight than incretin activity alone.

That is a plausible mechanism.

The clinical trials — not the mechanism — are what determine whether it actually works and whether the benefit is worth the risks.

Can you get retatrutide in Ireland?

Not as an approved medicine.

Eli Lilly states that retatrutide is investigational and is not approved by any regulatory agency for public use.

That means there is currently:

• no authorised Retatrutide-branded medicine;
• no normal Irish pharmacy supply;
• no approved Irish retail price;
• no licensed commercial prescription pathway.

Lilly says retatrutide is legally available only through its clinical trials.

If a legitimate clinical trial is recruiting, participation depends on strict eligibility criteria and trial locations — it is not the same as receiving a normal prescription.

The HPRA provides a public route for checking clinical trials taking place in Ireland and the wider EU.

But people are already using “retatrutide” in Ireland

Yes — and that is precisely why the distinction between trial medicine and black-market product matters.

RTÉ Investigates reported in 2024 that an unapproved product presented as retatrutide was being sold in Ireland.

In August 2026, RTÉ again reported warnings about people using retatrutide obtained outside regulated clinical trials.

Lilly’s position is explicit: anything claiming to be retatrutide sold to consumers outside its authorised clinical-trial supply chain is not an approved Lilly medicine.

The risks are not only the theoretical side effects of retatrutide itself.

With an unregulated vial, you may not reliably know:

• whether it contains retatrutide at all;
• the concentration;
• whether the vial is sterile;
• whether contaminants are present;
• whether the compound has degraded;
• whether the labelling is accurate.

The HPRA has separately warned about large volumes of illegal and falsified medicines entering Ireland, including GLP-1-type products.

Can you buy retatrutide online in Ireland?

There may be websites or social-media sellers willing to take money for products labelled “retatrutide,” “reta” or “research peptide.”

That does not make those products an approved medicine.

There is currently no legitimate consumer version of retatrutide to price-shop.

If a website is advertising “retatrutide 10 mg” or a similar vial for personal weight loss, that is fundamentally different from an authorised Wegovy or Mounjaro product supplied through the regulated prescription and pharmacy system.

Retatrutide price in Ireland: how much will it cost?

There is no official Irish price.

Retatrutide has not been approved or commercially launched.

Therefore:

Any current “retatrutide price in Ireland” is not the pharmacy price of an approved retatrutide medicine.

If the medicine receives European authorisation in future, Irish pricing would depend on factors such as:

• Lilly’s launch price;
• available presentations;
• private pharmacy pricing;
• whether public reimbursement is sought;
• any HSE reimbursement decision.

None of those has produced an official Irish retail price yet.

The Phase 2 result that first made retatrutide famous

The first major obesity result came from a peer-reviewed Phase 2 trial published in the New England Journal of Medicine in 2023.

The trial enrolled adults with obesity, or overweight plus a weight-related condition.

At 48 weeks, average weight change was:

Retatrutide dose	Average weight change at 48 weeks
1 mg	-8.7%
4 mg combined	-17.1%
8 mg combined	-22.8%
12 mg	-24.2%
Placebo	-2.1%

At the highest 12 mg dose:

• 100% of participants achieved at least 5% weight loss;
• 93% achieved at least 10%;
• 83% achieved at least 15%.

Those numbers were striking enough on their own.

But the trial was Phase 2 and relatively small.

The key question was whether similar effects would survive much larger Phase 3 testing.

Retatrutide Phase 3 results: what TRIUMPH-1 reported

In May 2026, Lilly announced topline results from TRIUMPH-1, its large Phase 3 obesity trial.

The trial involved more than 2,300 adults with obesity or overweight plus a weight-related condition, without diabetes.

At 80 weeks, Lilly reported the following efficacy-estimand results:

Group	Average weight change
Retatrutide 4 mg	-19.0%
Retatrutide 9 mg	-25.9%
Retatrutide 12 mg	-28.3%
Placebo	-2.2%

At 12 mg:

• 62.5% achieved at least 25% weight loss;
• 45.3% achieved at least 30%;
• 27.2% achieved at least 35%.

For context, a person starting at 100 kg would correspond to an average reduction of about 28 kg if they experienced exactly the 28.3% mean result.

That is only an illustration.

Individual results vary substantially.

Why you may also see “25%” quoted

Lilly reported more than one statistical estimand.

Under its treatment-regimen estimand, which incorporates what happened regardless of treatment adherence and certain additional interventions, the 12 mg group lost an average of:

25.0%

rather than 28.3%.

Both figures came from the same trial but answer slightly different questions.

Using only the larger number without explaining that distinction makes the result look more certain than it is.

Did people keep losing weight after 80 weeks?

A prespecified extension followed a subset of people with a starting BMI of at least 35 who had completed the main study and tolerated treatment.

At 104 weeks, Lilly reported average weight loss of up to:

30.3%

under the efficacy estimand.

That extension population was selected and should not be treated as the expected result for every future patient.

But it suggests the weight curve had not necessarily plateaued for everyone by week 80.

What did retatrutide do in people with type 2 diabetes?

This is important because weight loss is usually smaller in obesity trials involving type 2 diabetes.

A Phase 3 trial called TRANSCEND-T2D-1 was published in The Lancet in June 2026.

At 40 weeks, average weight change was:

• -11.5% with 4 mg;
• -13.9% with 9 mg;
• -15.3% with 12 mg;
• -2.6% with placebo.

HbA1c also fell substantially, by up to about 1.94 percentage points from baseline in the 12 mg group.

This was a peer-reviewed Phase 3 result.

It supports the biological effect of retatrutide beyond the company’s obesity press releases.

Retatrutide vs Mounjaro vs Wegovy: what the numbers show

This is the comparison most people will want.

But there is a major warning:

These are results from different trials, conducted in different populations, over different lengths of time, with different statistical methods. They are not a head-to-head ranking.

With that caveat:

Medicine / study	Mechanism	Trial population	Duration	Reported average weight change
Retatrutide 12 mg — TRIUMPH-1	GIP + GLP-1 + glucagon	Obesity/overweight, no diabetes	80 weeks	-28.3% efficacy estimand; -25.0% treatment-regimen
Retatrutide 12 mg — Phase 2	GIP + GLP-1 + glucagon	Obesity/overweight, no diabetes	48 weeks	-24.2%
Tirzepatide 15 mg — SURMOUNT-1	GIP + GLP-1	Obesity/overweight, no diabetes	72 weeks	-20.9%
Semaglutide 2.4 mg — STEP 1	GLP-1	Obesity/overweight, no diabetes	68 weeks	-14.9%
Liraglutide 3.0 mg — SCALE	GLP-1	Obesity/overweight, no diabetes	56 weeks	-8.0%

Separate trials therefore suggest an approximate progression:

liraglutide < semaglutide < tirzepatide < retatrutide

for average weight loss in the specific studies shown.

But that sequence is not yet a proven head-to-head hierarchy.

What we already know from Mounjaro vs Wegovy head-to-head

There is now a direct head-to-head obesity trial for two approved medicines.

In SURMOUNT-5, tirzepatide was compared directly with semaglutide over 72 weeks in 751 adults with obesity and without type 2 diabetes.

Average weight reduction was approximately:

• 20.2% with tirzepatide;
• 13.7% with semaglutide.

That result confirms that trial-to-trial comparisons can sometimes be tested properly when the drugs are studied in the same protocol.

Retatrutide has not yet had that published head-to-head moment.

That is why the pending TRIUMPH-5 retatrutide-versus-tirzepatide trial matters much more than simply placing separate headline percentages beside each other.

Retatrutide vs Mounjaro: is retatrutide actually better?

We do not know yet.

This is perhaps the most important point in the entire article.

Mounjaro contains tirzepatide, a dual GIP/GLP-1 agonist.

Retatrutide adds glucagon receptor agonism.

The separate trial averages make retatrutide look stronger.

But comparing separate trials can mislead because participants, baseline BMI, follow-up time, discontinuation rules and statistical methods differ.

Fortunately, the proper trial is already happening.

TRIUMPH-5

TRIUMPH-5 is a Phase 3 study directly comparing:

retatrutide vs tirzepatide

in around 800 adults with obesity.

There is no placebo arm.

The primary outcome is percentage change in body weight.

Lilly’s public trial information lists completion in late 2026.

Until that trial reports, claims that retatrutide has definitively “beaten Mounjaro” are premature.

For Compound, TRIUMPH-5 is the study to watch.

Retatrutide vs Wegovy

Wegovy contains semaglutide 2.4 mg.

Semaglutide activates the GLP-1 receptor.

In STEP 1, average weight loss with semaglutide was 14.9% at 68 weeks, compared with 2.4% with placebo.

Retatrutide’s reported averages in separate trials are substantially larger.

Again, this is not a direct comparison.

Wegovy also has an established regulatory, manufacturing and safety history that retatrutide does not yet have.

A medicine cannot be judged on weight loss alone.

Retatrutide vs Ozempic

Ozempic also contains semaglutide, but it is a different medicinal product from Wegovy.

Ozempic is authorised for type 2 diabetes.

Wegovy is the semaglutide product specifically authorised for weight management.

That means “retatrutide vs Ozempic” is not the cleanest efficacy comparison for obesity.

If you are comparing obesity-trial weight loss, retatrutide vs Wegovy is the more relevant semaglutide comparison.

For Irish access and indication differences, see How to get Ozempic in Ireland and Wegovy, Mounjaro and Ozempic prices in Ireland.

Is retatrutide just “stronger Mounjaro”?

Not exactly.

Mounjaro and retatrutide share GIP and GLP-1 receptor activity.

But retatrutide also activates the glucagon receptor.

That could affect energy expenditure and metabolism in ways that are not simply equivalent to increasing the dose of tirzepatide.

The medicines are distinct molecules.

Milligram doses cannot be compared directly.

For example:

12 mg retatrutide is not “weaker” than 15 mg tirzepatide because the number is smaller.

Milligrams only describe the mass of the specific molecule being administered.

What side effects has retatrutide caused?

Because retatrutide is investigational, it does not yet have a final approved patient-information leaflet.

The best evidence currently comes from trials.

Phase 2

The most common adverse events were gastrointestinal and were generally:

• dose-related;
• mild to moderate;
• more manageable with a lower starting dose.

The Phase 2 trial also reported dose-dependent increases in heart rate, which peaked around week 24 and then declined.

That remains an important safety signal to monitor.

TRIUMPH-1 Phase 3

Lilly reported the following adverse-event rates at the 12 mg dose:

Event	Retatrutide 12 mg	Placebo
Nausea	42.4%	14.8%
Diarrhoea	32.0%	13.5%
Constipation	26.1%	10.9%
Vomiting	25.3%	4.8%
Dysesthesia / altered sensation	12.5%	0.9%

Discontinuation because of adverse events occurred in:

11.3% of participants at 12 mg versus 4.9% with placebo.

Those figures come from Lilly’s Phase 3 topline release.

They are useful, but a final regulatory safety profile will require full review of the complete data package.

What is dysesthesia?

One relatively unusual signal reported in TRIUMPH-1 was dysesthesia.

This is an umbrella term for abnormal sensations, which can include:

• tingling;
• burning;
• altered skin sensation;
• uncomfortable sensitivity.

Lilly reported dysesthesia more frequently at the higher retatrutide doses.

Most events were described as mild to moderate and many resolved while treatment continued.

It is still an area worth watching as more detailed Phase 3 publications appear.

Is retatrutide safe?

The correct answer in 2026 is:

Its safety is still being established.

There is now substantial clinical-trial exposure, including several successful Phase 3 studies.

That is very different from saying the medicine has completed regulatory safety review.

Before approval, regulators will assess:

• all adverse events;
• serious adverse events;
• cardiovascular signals;
• pancreatitis and gallbladder events;
• renal effects;
• gastrointestinal tolerability;
• dosing and escalation;
• drug interactions;
• pregnancy and reproductive data;
• manufacturing quality;
• long-term benefit-risk balance.

The medicine’s final contraindications and warnings do not exist yet in the form of an approved Irish/EU product label.

Why the glucagon component could matter for safety

Glucagon receptor agonism is part of what makes retatrutide scientifically interesting.

It also means researchers need to understand effects beyond appetite suppression.

Potential areas of interest include:

• heart rate;
• glucose regulation;
• liver metabolism;
• lean mass;
• energy expenditure;
• cardiovascular outcomes.

Lilly is running large outcomes studies rather than relying on weight loss alone.

One of those programmes includes a cardiovascular and renal outcomes trial involving thousands of participants.

That kind of evidence will be important if retatrutide eventually becomes a widely used long-term medicine.

Will retatrutide replace Mounjaro or Wegovy?

There is no basis for saying that yet.

If approved, retatrutide could become another major treatment option.

Whether it becomes preferable for a particular person would depend on much more than average weight loss:

• tolerability;
• medical history;
• diabetes;
• cardiovascular disease;
• response to treatment;
• side effects;
• cost;
• reimbursement;
• supply;
• patient preference.

Some people may also achieve sufficient benefit on lower-dose or existing medicines without needing the strongest possible weight-loss effect.

When will retatrutide be available in Ireland?

There is no confirmed Irish date.

As of September 2026:

• retatrutide remains investigational;
• Lilly has reported several positive Phase 3 studies;
• Lilly has said it plans a US regulatory submission in Q1 2027;
• the company says it now has data to support broader global regulatory submissions.

A US submission does not automatically make the medicine available in Europe or Ireland.

For ordinary Irish pharmacy availability, there would first need to be an appropriate European regulatory pathway and authorisation, followed by commercial launch.

Public reimbursement would be a separate question again.

So anyone giving a guaranteed Irish launch month today is speculating.

Could Ireland get retatrutide before approval through a trial?

Clinical trials are the legitimate route by which investigational medicines are given to participants before approval.

But trials have strict entry criteria and specific sites.

They are not a substitute for commercial access.

If you want to check whether a retatrutide trial is recruiting in Ireland, use official clinical-trial registers such as the HPRA trial finder / EU Clinical Trials Information System, rather than paying a private seller claiming to offer “trial-grade” retatrutide.

Will retatrutide be covered by the HSE?

It is much too early to know.

Retatrutide first needs regulatory authorisation.

After that, public funding would depend on a separate Irish reimbursement process, including evidence, price and cost-effectiveness.

The current HSE funding position for approved GLP-1 and obesity medicines cannot simply be projected onto a medicine that has not launched.

Why retatrutide could matter so much

The potential importance of retatrutide is not just that the 28.3% number is larger than earlier obesity-drug trial averages.

It is that pharmacological treatment is moving into a range of weight loss that historically was difficult to achieve without bariatric surgery.

That raises new questions:

• How much weight loss is optimal?
• How should lean mass be protected?
• Which patients need maximum efficacy?
• What happens when treatment is stopped?
• Can cardiovascular and kidney outcomes improve?
• Will very large weight loss change the economics of obesity treatment?
• How tolerable will the highest doses be in routine care?

Retatrutide may become one of the medicines that forces those questions into everyday clinical practice.

Or later data could expose limitations that are less visible in headline weight-loss numbers.

That is why the next phase of evidence matters.

The three retatrutide developments to watch next

1. TRIUMPH-5: retatrutide vs tirzepatide

This is the big one.

It should tell us much more reliably whether the triple agonist actually produces greater weight loss than Mounjaro’s active ingredient under the same trial conditions.

2. Full peer-reviewed publication of the obesity Phase 3 programme

Topline company data are useful.

Full journal publication allows closer scrutiny of:

• missing data;
• discontinuations;
• adverse events;
• subgroup outcomes;
• statistical methods.

3. Regulatory submissions

The next major practical milestone is not another viral percentage.

It is regulators receiving and reviewing the full evidence package.

That is the point at which questions about real Irish availability begin to become concrete.

Retatrutide FAQs

Is retatrutide available in Ireland?

No. Retatrutide is not an approved medicine in Ireland and there is no authorised pharmacy product for public use.

Can I get retatrutide from my GP?

Not as an approved commercial prescription. Retatrutide remains investigational.

Is retatrutide stronger than Mounjaro?

Separate studies have reported greater average weight loss with retatrutide, but that does not prove superiority. The Phase 3 TRIUMPH-5 trial is directly comparing retatrutide with tirzepatide.

How much weight can you lose on retatrutide?

Lilly’s TRIUMPH-1 Phase 3 topline analysis reported average weight loss of up to 28.3% at 80 weeks at 12 mg under the efficacy estimand. The treatment-regimen analysis was 25.0%. Results vary between individuals.

Is retatrutide better than Wegovy?

Separate obesity trials reported larger average weight reductions with retatrutide than with semaglutide 2.4 mg, but the medicines were not tested against each other in those trials.

Is retatrutide the same as Ozempic?

No. Ozempic contains semaglutide and activates the GLP-1 receptor. Retatrutide is a different investigational molecule that activates GIP, GLP-1 and glucagon receptors.

Is retatrutide “GLP-3”?

No. “GLP-3” is an informal and scientifically inaccurate nickname. Retatrutide is a GIP/GLP-1/glucagon triple receptor agonist.

What is “reta”?

“Reta” is simply a shortened nickname people use online for retatrutide.

How much does retatrutide cost in Ireland?

There is no official Irish pharmacy price because retatrutide has not been approved or commercially launched.

Can you buy research retatrutide online?

Products advertised online are not an approved retatrutide medicine. Lilly warns against products claiming to be retatrutide outside its clinical trials because purity, dose and contents cannot be reliably assured.

More on GLP-1 medicines in Ireland

• GLP-1 medicines in Ireland: evidence, benefits and access — Put retatrutide in the wider Irish treatment landscape.
• How to get Ozempic in Ireland — How approved prescription access currently works.
• Wegovy, Mounjaro and Ozempic costs in Ireland — Compare currently available medicines and prices.
• GLP-1 side effects and when to seek help — Safety information for approved GLP-1-based treatments.
• What happens after stopping a GLP-1? — What long-term discontinuation evidence shows.

Bottom line

Retatrutide has moved from an interesting Phase 2 drug to one of the most closely watched late-stage obesity medicines in the world.

The evidence so far is genuinely impressive:

• 24.2% average weight loss at 48 weeks in the peer-reviewed Phase 2 12 mg group;
• up to 28.3% at 80 weeks in Lilly’s TRIUMPH-1 Phase 3 efficacy analysis;
• meaningful glucose and weight reductions in a peer-reviewed Phase 3 type 2 diabetes trial.

But the equally important fact for an Irish reader is:

Retatrutide is not currently an approved medicine in Ireland and cannot be obtained through the normal prescription and pharmacy system.

The comparison with Mounjaro is also not settled.

The separate trials make retatrutide look extremely powerful.

The direct TRIUMPH-5 retatrutide-versus-tirzepatide trial is what could tell us whether that apparent advantage holds up when the drugs are tested against each other.

For now, the useful position is to watch the data — not to treat unregulated online products as an early-access version of a future medicine.

For currently available Irish options, see Wegovy, Mounjaro and Ozempic costs in Ireland and How to get Ozempic in Ireland.