What Is Retatrutide? A Complete Guide to the New Weight Loss Injection

Popularity in weight loss injections in the UK is high. According to UCL News, about 1.6 million UK adults used weight loss drugs such as Mounjaro and Wegovy in the past year. The next wave of weight loss treatments is coming, and among them is Retatrutide. It's popular in conversations about medicated weight loss, but some people may not know much about it.

Retatrutide, also known as Triple G, is an investigational medication currently under study for weight loss. Early clinical trials have shown promising results, but retatrutide is not yet approved in the UK.

This guide explains how retatrutide works and which approved weight loss medications you may be able to access now.

Key Takeaways

• Retatrutide, or Triple G, is an investigational weight loss injection and is not yet approved for use in the UK.
• It targets three hormone receptors (GLP-1, GIP, and glucagon).
• Clinical trials have shown promising weight loss results of up to 28% on the highest dose, but further regulatory review is still needed.
• Retatrutide is only available through approved clinical trials. Avoid purchasing it online.
• Approved alternatives, including Mounjaro and Wegovy, are already available in the UK for eligible patients.

What Is Retatrutide?

Retatrutide is an investigational weight loss medication currently undergoing clinical studies as a once-weekly subcutaneous injection for adults with obesity or who are overweight. This includes patients with related conditions such as type 2 diabetes and fatty liver disease. The medication is also undergoing testing for blood sugar control and metabolic health.

Retatrutide is the active ingredient in the medicine and is a triple receptor agonist. This means it acts on three hormone pathways involved in appetite, insulin, blood sugar, and fat metabolism. They are:

• GLP-1, or glucagon-like peptide 1. It helps reduce appetite and increase fullness, plus affects how quickly food leaves your stomach.
• GIP, or glucose-dependent insulinotropic polypeptide. It's linked to insulin release after meals.
• Glucagon receptors, which affect how the body uses stored energy.

Retatrutide differs from the available weight loss injections. Wegovy (semaglutide) is a GLP-1 receptor agonist, and Mounjaro (tirzepatide) acts on GLP-1 and GIP receptors. Retatrutide is a triple agonist because it targets GLP-1, GIP, and glucagon.

Here's a table of these differences:

Retatrutide is under development by Eli Lilly, the same company that makes Mounjaro.

Why Is It Called 'Triple G'?

Some people call Retatrutide 'Triple G' because of the three receptors it targets. The acronym or name for each of these three hormones starts with the letter G, so researchers and the media shorthand them as Triple G.

How Does Retatrutide Work for Weight Loss?

Retatrutide works by mimicking hormone signals that already exist in the body to help control hunger, digestion, insulin release, and how the body uses energy.

By targeting GLP-1, retatrutide slows down stomach emptying, helping you feel satisfied with smaller meals quickly and stay fuller for longer. When your appetite drops, you may eat less, which can support weight loss over time. This also eliminates constant cravings.

When retatrutide acts on GIP, it improves how well your body handles insulin, preventing sharp spikes and crashes in blood sugar. GIP also helps regulate lipid (fat) metabolism, making it easier for your body to break down fat cells.

The glucagon part of retatrutide is why the medication is so popular even in its trial stage. Glucagon normally tells the liver to release stored glucose when blood sugar is low. But with GLP-1 and GIP, it can increase your resting energy expenditure. This means your body breaks down and uses stored energy, even when resting. It's why some people say that retatrutide burns fat.

What Do Retatrutide Weight Loss Results Show So Far?

Retatrutide has promising results in clinical trials. According to the phase 2 trial, published in the New England Journal of Medicine, adults with obesity who received retatrutide experienced an average reduction in body weight of up to 24.2% over 48 weeks.

Eli Lilly released data from their phase 3 trial (TRIUMPH-4) showing a mean weight reduction of up to 28.7% in adults with obesity or overweight after 68 weeks on the highest dose of 12mg. This is higher than any current medications.

Another potential benefit of retatrutide is support for blood sugar control. Also, some trials are examining retatrutide's effect on related health conditions, such as cardiovascular disease, sleep apnoea, osteoarthritis, and liver fat.

While the results are promising, regulators must review the safety, effectiveness, manufacturing quality, and risks of a medication before it gets approval. They must also monitor the severity of common and rare side effects, which may be manageable for some people but difficult for others.

Retatrutide Side Effects

Like other weight loss medications, retatrutide affects your digestive system, which can cause side effects. According to clinical trials, most symptoms have been mild to moderate in severity. Also, these side effects are usually stronger during the first few weeks of starting the treatment or when increasing the dosage.

Common Side Effects

Gastrointestinal (GI) complications are the most commonly reported and include:

• Nausea
• Vomiting
• Diarrhoea
• Constipation
• Dysesthesia (Skin Sensitivity)
• Mild heartburn
• Indigestion
• Fatigue
• Dizziness
• Mild irritation or redness at the injection site

Serious Risks

Though rare, some serious side effects could occur on retatrutide, including:

• Heart Rate and Rhythm Changes: Because retatrutide targets the glucagon receptor, trials noted a temporary increase in resting heart rate during the early weeks of treatment, as well as a minor risk of cardiac arrhythmias.
• Pancreatitis: About 0.4% of trial participants experienced acute inflammation of the pancreas.
• Gallbladder Issues: Roughly 1% of trial participants had gallstones or gallbladder inflammation due to rapid weight loss.
• Severe Dehydration: Consistent vomiting or diarrhoea can quickly lead to dehydration, which can strain kidney function.

The long-term safety of retatrutide will become clearer once regulatory bodies fully review the data from the Phase 3 clinical trial program.

Is Retatrutide Available in the UK?

Retatrutide is not approved in the UK and therefore is not legally available to patients outside approved clinical trials. As of the writing of this blog, the only way to access retatrutide safely in the UK is as a trial participant.

The National Health Service (NHS) and private clinics cannot prescribe or supply retatrutide as a weight loss treatment in the UK.

The Medicines and Healthcare products Regulatory Agency (MHRA) has warned that medicines claiming to contain retatrutide outside authorised clinical trials are likely to be illegal and potentially dangerous.

Can You Buy Retatrutide Online?

You may see retatrutide advertised online, but buying it is strongly discouraged because it's not approved for use in the UK.

Sellers on social media and other online platforms claiming to sell retatrutide may be scammers. The medications may be counterfeit, contaminated, incorrectly dosed, or not retatrutide at all. This creates serious health risks. Avoid online sellers and unregulated websites claiming to sell retatrutide.

When Will Retatrutide Become Available?

There's no confirmed UK launch date for retatrutide, as the medication is still in phase 3 clinical trials. After those studies, Eli Lilly would need to apply for approval from the relevant regulatory bodies, including the MHRA.

Also, NHS access would require assessment from the National Institute for Health and Care Excellence (NICE). Until that happens, any exact release date or retatrutide cost estimate is only speculation.

What UK Patients Can Use for Weight Loss Now

There are approved weight loss treatment options in the UK including:

• Mounjaro: It contains tirzepatide and acts on GLP-1 and GIP, affecting appetite and blood sugar regulation. Mounjaro is currently one of the best weight loss injections available in the UK, with patients losing about 20.9% to 22.5% of their body weight.
• Wegovy: Wegovy contains semaglutide and is a GLP-1 medication for weight management in suitable patients. You can lose about 21% of your body weight with the highest injection dose (7.2 mg). There's also a Wegovy pill.
• Weight Loss Pills: Some patients prefer tablets or may not be eligible for injections. In that case, prescription weight loss pills such as Orlistat and Alli may be the best options.

Curely’s Weight Loss Support for UK Patients

Curely is a licensed UK clinic and pharmacy that helps you access clinically proven treatments.

Our process is simple, starting with a quick and thorough online consultation. A prescribing clinician will review your answers and help decide which treatment may be suitable for you. Once approved, we'll deliver your medicine to your home or work in discreet, unmarked packaging.

Curely offers flexible treatment plans and the option to pause when you need to, so you'll be in full control of your weight loss journey.

Our top priority is your health and safety, which is why we source all our medications from regulated, approved suppliers. Start your consultation with Curely today.

FAQs

Is Retatrutide Available Yet?

No. Retatrutide is still an investigational medication that may become available in the future, but only if regulatory bodies approve it. People interested in weight loss treatments can use Mounjaro, Wegovy, and prescription pills from Curely.

Is Retatrutide Better Than Mounjaro?

Early trials suggest retatrutide may lead to higher average weight loss than Mounjaro because it's a triple agonist. However, because retatrutide is not yet available, Mounjaro is the best option for achieving high weight loss results.

Is Retatrutide the Same as Ozempic?

No. Ozempic contains semaglutide, a GLP-1 receptor agonist, while retatrutide targets GLP-1, GIP, and glucagon receptors. Also, Ozempic is approved for the treatment of Type 2 diabetes in the UK, not weight loss.

How Are People Getting Retatrutide?

The only legitimate way to access retatrutide is through an approved clinical trial. Online products claiming to be retatrutide are not regulated medicines and may be unsafe.

Conclusion

Retatrutide is a triple agonist developed by Eli Lilly, and early trials suggest it may help some patients lose a lot of their body weight. But it's not approved in the UK and therefore unavailable through the NHS or private clinics. Buying retatrutide online is unsafe and strongly discouraged.

Curely offers regulated weight loss medications, including Mounjaro, Wegovy, and prescription pills that are safe and approved under UK law. Complete Curely’s consultation today to find out which weight loss treatment may be suitable for you.

Reference List

• Eli Lilly. “What Are the Preliminary Results with Retatrutide from TRIUMPH-4 in Participants with Obesity or Overweight and Osteoarthritis?” Lilly.Com, 2026.
• Jastreboff, Ania M, et al. “Triple–Hormone-Receptor Agonist Retatrutide for Obesity — a Phase 2 Trial.” The New England Journal of Medicine, vol. 389, no. 6, 26 June 2023.
• Medicines and Healthcare products Regulatory Agency. “MHRA Smashes Major Illicit Weight Loss Medicine Production Facility in Record Seizure.” GOV.UK, 24 Oct. 2025.
• UCL. “1.6 Million UK Adults Used Weight Loss Drugs in Past Year.” UCL News, 8 Jan. 2026.