The use of an unapproved drug dubbed the ‘Godzilla’ of weight-loss jabs is raising alarm among doctors, who warn the UK is witnessing a ‘huge, unregulated human experiment‘.
Retatrutide, known as ‘Reta’, is an appetite-suppressing medication like Mounjaro and Ozempic. But, unlike those drugs, it is still undergoing clinical trials, meaning it has not been approved by health officials.
However, soaring demand for weight-loss injections – now believed to be used by around 2.5 million Britons – has fuelled a booming black market for the new drug.
Trials suggest that retatrutide can help patients lose up to a third of their body weight in less than a year, prompting people to buy the drug from unlicensed sellers despite the risk that the products could be fake, contaminated or wrongly dosed.
Though it is not expected to receive official approval until later this year or early next year, investigations have found TikTok influencers, spas and beauty clinics selling retatrutide online under secret codenames to avoid detection by authorities.
The drug is said to be particularly popular with gym-going young men, with early research suggesting it may help patients lose fat while retaining muscle mass.
But doctors are now warning that, without official approval, those currently using retatrutide are putting themselves at serious risk.
It comes just weeks after health officials in Australia revealed six people had been hospitalised with severe liver damage after taking unlicensed doses of the drug.
Retatrutide is an appetite-suppressing medication like Mounjaro and Ozempic – but unlike those drugs it is still undergoing clinical trials
Courtney Younglove, founder and medical director of Heartland Weight Loss in Kansas, said: ‘What’s happening now is a huge, unregulated human experiment.’
Speaking to medical news site Medscape, she added: ‘Yes, we know retatrutide works to cause weight loss, but the more important data – who are the best candidates, what doses do we use, how to titrate them, what adverse effects to watch for – we don’t know.’
Like existing weight-loss jabs, retatrutide – which is manufactured by Zepbound and Foundayo maker Eli Lilly – targets the glucagon-like peptide-1 (GLP-1) hormone.
Unlike its rivals, however, it also targets another two – GIP and glucagon – earning it the nickname of a ‘GLP-3’.
Experts in the US say they have never seen such a widespread demand for a drug which has not yet been approved by the Food and Drug Administration (FDA).
Anne Peters, a professor of clinical medicine and a clinical scholar at the Keck School of Medicine, said: ‘I’ve never seen this, not ever. I’ve seen this happen with supplements, but not a drug that’s under study to be FDA-approved.’
Trials show that patients taking the powerful new drug can lose up to a third of their body weight.
Patients taking a 12mg dose typically lost more than a quarter of their body weight (28.3 per cent) in just 18 months – the equivalent of 31.9kg or 5 stone.
Nearly half of all participants, meanwhile, achieved at least 30 per cent weight loss over the course of the 80-week study, a level long associated with bariatric surgery.
Currently, the most powerful licensed weight loss drug, Mounjaro, helps users lose around 20.9 per cent of their body weight when taken for 72 weeks.
Trials have shown that the retatrutide, like other GLP-1s, comes with gastrointestinal side effects such as nausea, vomiting, diarrhoea, and constipation.
But recent reports suggest that unlicensed use of the drug could also lead to more serious health issues.
Officials in Australia put out an urgent health warning earlier this month after six people were hospitalised with acute liver damage after taking the drug.
Megan Hancocks (pictured) said she used off-market peptide retatrutide late last year
The unapproved peptide products had been bought online, through friends and social media accounts, said Victoria’s Chief Health Officer Dr Caroline McElnay.
One retatrutide user, Megan Hancocks, 32, became interested in the peptide after seeing it on social media, but couldn’t access it through legitimate means.
During a routine beauty appointment late last year, Ms Hancocks said she was offered off-market peptides sourced from a Chinese manufacturer, available for cash.
She said she had bought a vial labelled retatrutide, along with another peptide commonly used for skin treatments.
‘I was quite small looking back now, but obviously your mind tells you otherwise,’ she told ABC News.
She took her first dose on Christmas Eve, followed by another just days later.
But, within a week, Ms Hancocks was rushed to the Royal Melbourne Hospital with acute liver failure.
Her symptoms included severe jaundice including a yellow colour to her eyes, nausea and vomiting, extreme fatigue, stomach swelling and debilitating constipation.
Doctors treated her for about a month and considered the possibility of a liver transplant, but her condition stabilised before the procedure was needed.
Another study led by the University of Pennsylvania, which analysed Reddit posts from more than 13,000 people claiming to have used retatrutide, found users also reported fatigue, increased energy, food cravings and an elevated heart rate.
Experts say this raises questions about whether some people are taking fake versions of the drug.
Professor Peters said: ‘Compounded retatrutide often comes in a powder that users reconstitute. For all I know, they might be taking baby powder.’
A New York Times article published earlier this month found that hundreds of thousands of retatrutide doses may have entered the US during the first four months of the year.
While some of those were believed to have been shipped to scientists studying the drug, there are fears that large amounts may be flooding the black market.
Timothy Macket, a professor at the University of California San Diego who studies fake medications, said: ‘The bottom line is, the demand is fully there. And there are lots of ways to get it.’
A spokesperson for Eli Lilly warned that black market retatrutide may be fake and not contain any trace of the drug at all.
They said: ‘Any claim that black market retatrutide is the same as Lilly’s genuine medicine as studied in clinical trials is false.’
The FDA has already received around 40 reports of suspected adverse reactions linked to retatrutide, including heart problems, appendicitis and blurred vision.
Fourteen patients were hospitalised and four were classified as being in a life-threatening condition.
Despite the risks, users told the New York Times that they are prepared to gamble on the drug as a way to shift weight quickly.
Jacob Hanzel, 31, who buys what he believes is retatrutide through a WhatsApp group, sends each batch to a lab for testing and has regular health checks with his doctor.
Due to the risks that the products could be fake, Jacob Hanzel, a 31-year-old who purchased the medication from a WhatsApp group, tests the products at a local lab.
He said: ‘I was willing to take this risk. While knowing it’s still a risk.’
Research by online pharmacy MedExpress has found that men between 25 and 34 are the most likely to buy the drug illegally, while women are more likely to use it when officially approved.
Experts believe this may be linked to its popularity among gym-goers.
Dr Luke Turnock, a performance-enhancing expert at the University of Lincoln, said retatrutide is ‘following the pattern of steroids’.
He told The Sun: ‘Retatrutide is still an experimental medicine so may have long-term risks that are not yet fully understood.
‘Even if it does pass all clinical trials, the illicit market product will still have risks because purity is uncertain and doses recommended by sellers may be risky to use.’
