Retatrutide Weight Loss Injections: The Next Big Thing?

Weight loss injections such as Mounjaro and Wegovy have earned a strong reputation for helping individuals achieve their goals when diet and exercise alone haven’t worked. Clinical trials show that the treatments could lead to a 22.5% and 17% weight loss, respectively, when used alongside positive lifestyle choices.

Of course, science never sleeps, and new medications are constantly being introduced. Retatrutide is one such innovation. Manufactured by Eli Lilly, the company behind Mounjaro, the treatment has been garnering a lot of attention as it moves through development.

In this article, we’ll explore everything you need to know about Retatrutide weight loss injections, such as how they work, how effective they might be, how to use them, and whether they’re available in the UK. Let’s begin.

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What Does Retatrutide Do?

Retatrutide (also known as Triple G) is a novel weight loss medication currently in clinical development. Though not yet approved for prescription in the UK, emerging data suggests retatrutide could be the most effective weight loss injection yet.

This is because retatrutide is a triple-agonist drug, meaning it mimics the effects of three hormones. These are:

• Glucagon-like peptide 1 (GLP-1)
• Gastric inhibitory polypeptide (GIP)
• Glucagon

The combined action of the three agonists in retatrutide can have a profound effect on hunger, metabolism, and weight loss. GLP-1 slows the movement of food through the stomach, reducing appetite and cravings. GIP lowers blood lipid levels and promotes fat-burning, while glucagon increases the body’s energy expenditure (i.e., the number of calories burned).

As a result, retatrutide promotes rapid and significant weight loss. One phase 2 clinical study reported that people using this medication lost almost a quarter of their starting body weight in under a year. This is a higher rate of weight loss than that achieved with currently available weight-loss injections, such as Mounjaro, Nevolat, and Wegovy.

The likely reason for retatrutide’s enhanced efficacy is its ability to mimic the effects of three hormones simultaneously. This sets it apart from other weight loss injections, which mimic the effects of GLP-1 (semaglutide and liraglutide) or GLP-1 and GIP (tirzepatide).

What is Retatrutide Used For?

Retatrutide is a novel medication currently being tested for its applications in weight management. Researchers hope that by targeting three hormones simultaneously, they can develop the most potent weight loss injection to date.

Though the primary intended purpose of retatrutide is to combat obesity, this drug also has the potential to improve many weight-related health problems. This is because people who are clinically overweight or obese are at greater risk of other medical conditions, including:

• Type 2 diabetes (and related complications like diabetic retinopathy, diabetic foot syndrome, and various cancers)
• Cardiovascular disease and heart failure
• Kidney disease
• Metabolically-dysfunctional-associated fatty liver disease (MAFLD)
• Obstructive sleep apnoea

By facilitating rapid weight loss, retatrutide may alleviate or reduce the risk of serious obesity-adjacent medical complications. Therefore, it could produce better long-term health outcomes than other GLP-1 and GIP agonists.

How Effective is Retatrutide?

Retatrutide is still in clinical development, but emerging data suggest it is a powerful weight loss aid. Phase II trials into the efficacy of retatrutide for obesity reported an average weight reduction of 24.2% after 48 weeks of treatment. Participants also experienced improvements in weight-related health issues. For example, 72% of patients with prediabetes reverted to normal blood glucose levels by the end of treatment.

Ongoing clinical studies are now investigating retatrutide on a larger scale. The TRIUMPH trials, which include over 5800 participants, aim to demonstrate the safety and efficacy of retatrutide for obesity and related complications such as obstructive sleep apnoea and osteoarthritic knee pain. Retatrutide is also being studied for its potential to improve cardiovascular and kidney disease outcomes. If approved, retatrutide could make a substantial improvement to the long-term health and quality of life of people with weight management problems.

Is Retatrutide More Effective Than Tirzepatide and Semaglutide?

Retatrutide may prove more effective than tirzepatide and semaglutide for weight loss. Clinical trials report that this medication can help people lose up to a quarter of their body weight. This result surpasses those produced by both semaglutide (Wegovy) and tirzepatide (Mounjaro), possibly because of retatrutide’s triple-agonist action.

By targeting GLP-1, GIP, and glucagon simultaneously, retatrutide may promote better blood sugar control and weight loss outcomes than tirzepatide and semaglutide. However, the true efficacy of retatrutide won’t be conclusive until the clinical trials are complete.

How to Use Retatrutide Pens

Retatrutide pens aren’t yet available for use, as the drug is still in development. However, once approved, doctors will probably prescribe it as a weekly subcutaneous injection like Wegovy and Mounjaro.

No one has released a medical device for administering retatrutide yet, but it will likely be similar to other weight loss injection pens. Wegovy and Mounjaro both come in pre-filled injection pens, which you can use at home without medical supervision. These pens are designed to administer four individual doses, each containing a precisely measured quantity of your prescribed medication. Once all four doses are used up, the pens can be discarded.

Retatrutide Dose Schedule

Retatrutide does not currently have an approved dosing schedule, as the medicine is still under investigation. However, clinical trial subjects received weekly subcutaneous injections with dose increases every 4 weeks. The dose escalations in this study followed the following schedule:

• Weeks 1 to 4: 2 mg per week
• Weeks 5 to 8: 4 mg per week
• Weeks 9 to 12: 8 mg per week
• Week 13 onwards: 12 mg per week

Currently available weight loss injections like Wegovy and Mounjaro also follow a treatment regimen of weekly injections with 4-weekly dose increases. Therefore, it is likely that clinicians will develop a similar dosing schedule for retatrutide.

For reference, the Wegovy dosage schedule is as follows:

Meanwhile, the Mounjaro dosage schedule looks like this:

Is Retatrutide Available in the UK?

No, Retatrutide is not yet available in the UK. This drug is still under investigation and is currently the subject of the TRIUMPH phase III clinical trials; a series of large-scale studies into retatrutide’s efficacy for treating obesity and weight-related health complications.

The estimated completion date for this study is 2026, and retatrutide won’t be approved until the drug has passed all safety and efficacy tests. Therefore, its earliest possible availability in the UK will be late 2026 or 2027.

How Much Will Retratrutide Cost?

At this stage in the drug’s development, it’s hard to predict how much retatrutide will cost. However, it’s expected to compete with existing weight loss injections and will likely be priced similarly to Wegovy and Mounjaro. At Prescription Doctor, Wegovy is available from £129.99, while Mounjaro starts at £179.99.

Helping You Through Your Weight Loss Journey

If you’ve been struggling to lose weight through diet and exercise alone, following a medicated programme could be the answer. While Retatrutide weight loss injections aren’t available in the UK at this time, there is a wide range of licensed treatments that are designed to help you reach your goals.

Prescription Doctor is proud to offer a broad selection of medications as part of our weight loss clinic, including injections like Mounjaro, Nevolat, and Wegovy, as well as tablets such as Mysimba and Xenical. This is backed up by our team of highly skilled clinicians who are available to answer any queries you may have and support you throughout your journey.

Our service is built around your unique requirements. Place an order for your chosen treatment by filling out the online questionnaire, and our clinicians will review your information to determine whether the medication is suitable for your circumstances or recommend an alternative. We will also regularly check in with you to monitor progress and ensure everything is working as it should.

Ready to take the first steps towards a new you? Start a consultation with Prescription Doctor today and let us help you achieve your ambitions. 

Authored By

Kate Latham

Medical Content Writer

Kate has been a scientific content writer since 2017. With a BSc in Biology and a background in cancer research, she is adept at identifying the latest findings in medical research and utilising these

Published on: 06/01/2026

Reviewed By

Mohamed Imran Lakhi

MPharm - Lead Pharmacist

Imran Lakhi is the superintendent pharmacist and founder at Prescription Doctor. He has been at the core of our team.

Reviewed on: 06/01/2026