Excitement around a new drug, especially one showing early promise in clinical trials, is usually celebrated by its developers. But retatrutide, the experimental weight-loss jab from Eli Lilly, has become a headache not just for the company, but for regulators in the UK and worldwide. The drug hasn't been approved for human use by any regulatory body, yet counterfeit versions are flooding the black market. Experts tell the BBC this is one of the first times they've seen copycat versions of an experimental drug - still in testing - become so widely available.
Vials purporting to be 'reta', as it's affectionately known, are being sold in UK gyms, nail and beauty salons, hairdressers, on social media, and even by street flower sellers. 'The world has gone mad,' says Sehar Shahid, pharmacist and director of 24 HR Pharmacy. 'People are effectively injecting an illegal drug and thinking it's safe. It's become so normalised people openly talk about their dealers, where's best to get it from, and post all over social media.' Indeed, a quick scroll through social media reveals orders placed in minutes, with no proof of contents, effects, or origin.
Keen users post before-and-after 'reta' pics on TikTok, describing how it silenced food noise and melted away pounds. The problem? Despite positive trial results, real retatrutide is still being tested for safety and efficacy. Only 50% of drugs at Phase III stage in the US eventually get FDA approval; the rest fail due to poor performance in larger populations or unexpected safety issues. And the fakes? They may not resemble the lab-developed version at all.
Eli Lilly's website warns: 'No one should take anything claiming to be retatrutide outside of a Lilly-sponsored clinical trial. Illicit retatrutide products may contain unknown ingredients, harmful contaminants, and impurities. These products may also have too much or too little active ingredient, or the wrong ingredient entirely.' Yet plenty are willing to gamble.
'Young fit patients are coming into hospital with nausea, vomiting, diarrhoea, in some cases kidney failure,' says endocrinologist Prof Donal O'Shea. He notes some personal trainers are supplying and injecting clients without them knowing doses or contents. Tom Davies, 20, from Brighton, nearly ended up in hospital after overdosing on a fake he ordered from a Chinese supplier recommended by gym friends. 'It was horrendous. My body felt so under pressure, I was so bloated, it was like someone had dropped a 20kg weight on my stomach. For 72 hours I had really bad diarrhoea and nausea. I thought, if this continues I'm going to end up in A&E.' He had given himself eight times the recommended dose, as copycat retatrutide often requires mixing with bacteriostatic water and careful calculations.
Dr Nas Khattak, a research doctor in Chester screening patients for Eli Lilly's Phase III trial, compares self-dosing to being a lab rat without oversight. Trial participants must meet strict criteria: 'We request their GP record, we make sure that they're emotionally well. They'll have suicide, self-harm, mental health assessments - all done by doctors. Then we review blood tests and decide suitability.' Tom, despite his ordeal, did more research and continued using his fake version for nine months, reporting his sugar and junk food cravings vanished. Pharmacist Shahid warns that just because a fake works for one person doesn't mean it will for the next.
Retatrutide, if approved, would be the first weight-loss drug to act on three hormone receptors, earning the nickname 'triple G'. It targets GLP-1 (slows stomach emptying, signals fullness), GIP (enhances insulin secretion), and glucagon (increases energy expenditure, promotes fat breakdown). Lisa King, taking a fake since July, lost 3kg (6lb) a week while dieting and exercising, and believes it helps manage her polyendocrine metabolic ovarian syndrome (PMOS) symptoms - sugar cravings down, periods regulated, more energy. She's unfazed by the lack of approval: 'No, not at all. There are many things that have not been approved. If I start to experience any negative side effects I'll just come straight off it.'
Other users report brain fog, nausea, diarrhoea, loss of libido, and anhedonia. Doctors are increasingly worried. Dr Sahira Dar, GP and chair of the British Islamic Medical Association, urges healthcare professionals to ask about black market products 'without judgement' so patients feel able to 'disclose what they have taken'.
Eli Lilly, which has spent nearly a decade developing retatrutide, is fighting back. It's taking action against peptide companies, influencers, compound pharmacies, and wellness clinics, reporting over 14,000 websites, ads, and social posts illegally marketing the drug. A spokesperson said: 'Any retatrutide available online is unapproved, unverified, and simply not worth the risk.' The UK's MHRA has conducted raids and seizures of 'products claiming to contain retatrutide' over the past year, working to disrupt illegal importation and distribution.
Prof O'Shea cautions against demonising the entire drug class: 'GLP-1s are a major advance in managing obesity, a major advance in our insight into how the brain regulates cravings and appetite.' But approval is still far off. Eli Lilly plans to submit for US FDA approval early next year, with a review taking up to a year - meaning legal availability in the US no earlier than end of 2027. In the UK, depending on MHRA approval, it could hit the market by 2028. Until then, the black market thrives, and the 'world has gone mad' indeed.