Retatrutide is a once-weekly weight loss injection currently being developed by Eli Lilly, the pharmaceutical company behind Mounjaro. Unlike other weight loss medications such as Wegovy, retatrutide works by replicating not one, but three different hormone receptors. Together, this combination can help you feel less hungry, stay fuller for longer, and burn energy.

Expectations are high when it comes to results of the retatrutide weight loss injection, with the latest Phase 3 clinical trial showing that participants taking the highest studied dose lost an average of 28.3% of their starting body weight over 80 weeks¹. However, clinical trials are ongoing and retatrutide is not currently approved or available in the UK.

If you're wondering about retatrutide UK availability, what the medicine is, how it works, the latest clinical trial results and how it compares to other weight loss medications on the market, we've compiled everything you need to know.

What is retatrutide?

Retatrutide is an investigational medicine currently being studied as potential treatment for obesity/weight management and other weight-related health conditions, such as type 2 diabetes, sleep apnoea and certain chronic pains.^1.2

Currently under development by Eli Lilly, the treatment is often referred to as a triple hormone receptor agonist, or nicknamed 'Triple G,' because it mimics three different hormones:

• GLP-1 (glucagon-like peptide 1)
• GIP (glucose-dependent insulinotropic polypeptide)
• Glucagon

This combination is what makes retatrutide different from other weight loss medications currently available in the UK, such as Wegovy which only mimics one hormone, and Mounjaro which mimics two.

How does retatrutide work for weight loss?

How effective is retatrutide for weight loss?

According to the Phase 3 clinical trials published from the TRIUMPH-1 study³, retatrutide breaks all previous weight loss records.

At 80 weeks, average weight loss was:

• 19.0% with the 4mg dose
• 25.9% with the 9mg dose
• 28.3% with the 12mg dose
• 2.2% with placebo.^1.3

Among people taking the 12mg dose, 45.3% lost at least 30% of their starting body weight.^1.4

Some people in the study who started with a BMI of 35+ were followed for an additional 24 weeks. By week 104, those taking the highest dose had lost an average of 30.3% of their starting body weight.

It's important to remember that the clinical trial figures are averages, and individual results may vary. The Phase 3 programme is also still underway, and while early results are promising, retatrutide is not yet approved for use.

What is the retatrutide dosage?

As retatrutide isn't a licensed medicine yet, there is no official approved dosage. Different doses are being studied in clinical trials.

In TRIUMPH-1, participants were assigned to target doses of:

• 4mg
• 9mg
• 12mg

Treatment started with a weekly 2mg dose which was gradually increased every four weeks until participants reached their target dose.^1.5

This dosing schedule is based on the clinical trial only. When retatrutide is approved in the UK, its licensed doses and recommended dosing schedule will be confirmed.

How does retatrutide compare to other weight loss treatments?

What's the difference between retatrutide and Mounjaro?

Mounjaro and retatrutide are both weight loss drugs developed/under development by Eli Lilly, but they're different medicines.

The biggest difference is the number of hormone receptors they target.

Mounjaro (tirzepatide) activates:

• GIP receptors
• GLP-1 receptors

Retatrutide activates:

• GIP receptors
• GLP-1 receptors
• glucagon receptors.

This is why Mounjaro is generally described as a dual agonist, while retatrutide is described as a triple agonist.

While Mounjaro is currently an approved prescription medicine for weight management in the UK, retatrutide is still in the clinical trial phase and is not yet approved or available.

What's the difference between retatrutide and Wegovy?

Wegovy contains semaglutide, which only targets the GLP-1 receptors. It's currently available in the form of a weekly injection, or a daily Wegovy pill.

Retatrutide targets GLP-1 as well as GIP and glucagon receptors, meaning it works through three different hormonal pathways rather than one.

Both have been studied as once-weekly injections, but while Wegovy is already licensed for weight management in the UK, retatrutide remains under investigation.

What's the difference between retatrutide and the Foundayo pill?

Retatrutide and Foundayo are both weight loss medicines developed by Eli Lilly, but there are some important differences between them.

Foundayo contains orforglipron and comes as a tablet that's taken once a day. It works by targeting the GLP-1 receptor, which can help reduce appetite and make you feel fuller.

Retatrutide on the other hand, is being studied as a weekly injection targeting three different hormone receptors.

While Foundayo has been authorised in the UK, retatrutide is still in the clinical trial phase.

Who's eligible for retatrutide?

Retatrutide is still being studied and has not yet been approved in the UK, so there are currently no official UK eligibility criteria for the treatment.

The Phase 3 TRIUMPH-1 trial included adults who had:

• a BMI of 30 or above; or
• a BMI of 27 or above and at least one weight-related health condition, such as high blood pressure, abnormal cholesterol levels, obstructive sleep apnoea or cardiovascular disease.

It's important to note this criteria was for the clinical trial only, and may change if and when the medicine becomes available in the UK.

Switching to retatrutide from another weight loss treatment

As retatrutide isn't currently approved or available in the UK, it's not possible to switch to retatrutide from Mounjaro, Wegovy or Foundayo at the moment.

If the medicine becomes available in future, just like with any medicine, switching treatment would need to be discussed with a healthcare professional. They will assess response to your current treatment, any side effects experienced, your health history and your personal circumstances.

You should not stop taking your current weight loss medicine to try and obtain retatrutide from an unregulated source. Continue taking any prescribed medicines as directed and speak to your prescriber if you have any questions or concerns.

What are the side effects of retatrutide?

Like any medication, retatrutide may come with side effects.⁴ However, because the drug is still being investigated in clinical trials, its full safety profile hasn't been established yet.

Reported side effects were similar to those of other weight loss medicines such as Wegovy and Mounjaro.

In the TRIUMPH-1 trial, the most commonly-reported side effects were mainly gastrointestinal, including:

• nausea
• diarrhoea
• constipation
• vomiting

At the 12mg dose, Eli Lilly reported nausea in 42.4% of participants, diarrhoea in 32.0%, constipation in 26.1% and vomiting in 25.3%. Changes in skin sensation, known as dysesthesia, were also reported during the study.^1.6

Further research is needed to understand the full safety profile and longer-term effects of retatrutide.

Is retatrutide available in the UK?

No. Retatrutide is not currently approved or available as a weight loss treatment in the UK.

It remains an investigational medicine undergoing clinical development.

The MHRA has confirmed that retatrutide has not been approved for UK use and that products claiming to contain retatrutide being sold outside authorised clinical trials are likely to be illegal and potentially dangerous.⁵

Can you buy retatrutide online?

You may see websites or social media accounts offering products labelled as 'retatrutide,' but as the medicine is still in its clinical trial phase, buying these products could be extremely unsafe.

Products released before official licensing are unregulated and may be untested, unauthorised and potentially dangerous.

Prescription medicines should only be obtained from a registered pharmacy following a prescription from an appropriate healthcare professional.

When will retatrutide be available in the UK?

There is currently no confirmed UK release date for retatrutide.

Before it can be routinely prescribed in the UK, the medicine needs to complete the necessary clinical development and regulatory processes. Any specific UK launch date you see online should be treated as an estimate unless it has been confirmed by official sources.

We'll continue to update this page as more information becomes available to help you stay in the loop.

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How much will retatrutide cost in the UK?

The UK price of retatrutide is not currently known.

Because the medicine hasn't been approved or launched, there is no official UK retail or prescription price.

You may see estimated retatrutide prices online, but these shouldn't be confused with an official UK price.

If retatrutide is approved for use in the future, more information on price and availability will become available.