When I started taking Mounjaro last year, the impact was astounding. With a reduced appetite and a muffling of the food noise which made crisps and biscuits impossible to resist, I lost two stone in six months, slimming down to 11-and-a-half stone.

The positive impact on my mental and physical health is so marked that I've become hopelessly addicted to my GLP-1 elixir and have continued with a low 'maintenance' dose (2.5mg), which I inject weekly into a pinched wedge of belly fat.

But now I'm facing a dilemma. For the past six months, I have stopped losing weight. There has been precisely zero shift on the bathroom scales. And though I'm lighter than I have been in decades, my weight is still in the 'overweight' category – at 5ft 7in – on the NHS BMI charts.

When my weight was falling off, I could justify the monthly cost of £180 for my Mounjaro syringe 'pen'. Now that it's stopped, and I'm squandering more than £2,000 a year for nothing, it feels like I need to try something new.

I could bump up my dose and spend even more. Or I could try the new, so-called 'Godzilla jab', retatrutide – which delivers a better weight-loss result than Mounjaro in trials, and costs a fraction of the price of my current private prescription.

The catch is that this big-hitting jab – the most powerful GLP-1 ever developed – is not yet licensed, which means it cannot be legally dispensed by a pharmacy, and for now can only be found on the 'grey market', as I will explain.

That isn't a problem in terms of availability. My research shows that it's ridiculously easy to get hold of – but it might well be an issue in terms of my health.

Developed by Eli Lilly, the same drug company behind Mounjaro, 'reta' – as it's known to users – showed incredible results in large-scale phase three trials published last month, with patients losing more than a quarter of their body weight in 18 months – a whopping 28.3 per cent – compared to a fifth (20.9 per cent) with Mounjaro.

Like Ozempic and Mounjaro, it works by mimicking hormones that regulate appetite and slow gastric emptying. But while Ozempic works on one hormonal receptor and Mounjaro on two, reta acts on three receptors, which gives it the added power to effectively increase energy expenditure and help the body burn more calories. This also helps to preserve muscle as the fat melts away.

It certainly sounds exciting. Yet the drug is so new, it won't be approved for sale via UK pharmacies until late 2027 or even 2028.

That means the only reta we can use now is 'fake' reta, not made by Eli Lilly but by Chinese chemical suppliers and unregulated research companies, probably following the formulation published by Eli Lilly in its patent applications and clinical trial papers.

But who cares, right? If it makes us slim?

That's certainly the attitude you encounter on social media, where dozens of perfectly respectable British influencers are extolling the virtues of their weekly reta fix – and directing followers to websites where you can buy it.

One TikToker Becky, for example, has numerous posts showing off her six-stone weight loss, with links to a site where you can order a 30mg reta pen for £150.

Another has a pinned post at the top of her profile, saying 'I cannot advise anybody… you have to make your own decision… but it does work', alongside telling her followers to message her for 'information' on how to get the jab.

So what are these sites selling knock-off reta? When I investigated the murky black market for replica Ozempic and Mounjaro last year, I discovered you risk losing money on scam websites and online shops with no guarantee that your illegally purchased package will arrive from its factory in China.

But reta is different. As it is not yet licensed, it does not come under the control of the Medicines and Healthcare products Regulatory Agency, which ensures all drugs meet strict safety, quality and efficacy standards before they can be prescribed.

That opens up a major loophole and means imported dupes can be openly sold – seemingly without fear of prosecution – as long as the packaging states 'for research purposes only'. You just need to know where to look.

When I put out a call among my Mounjaro-taking friends, a surprising number tell me they're interested in switching to reta because, like me, they are unwilling to pay as much as £370 per month for the higher dose they feel they need to get the scales moving again.

In fact, it took only a few calls for me to find a friend of a friend who had already taken the reta plunge.

Sally (not her real name), a 37-year-old nursery school teacher from Wigan, tells me she bought a reta syringe pen from a personal trainer – the son of her mother's friend.

'His mum tried it and it worked, so she recommended it to my mum, who then recommended it to me,' she says.

Sally lost one-and-a-half stone on Mounjaro last year, but suffered constant nausea and alarming hair loss (both common side-effects). 'I was miserable and it seemed crazy to be paying a fortune to feel so unwell. I was very dubious about the fact that reta is not yet approved, but I figured enough of my friends and neighbours are using it, so I should be ok.'

She paid £140 for a 20mg pen with enough 'Godzilla juice' to last ten weeks on a 2mg weekly 'starter dose' as 'prescribed' by her PT. She noticed the appetite suppression immediately.

'I loved the fact I didn't feel sick, no acid reflux or eggy burps, and the weight was falling off,' she says. 'It was amazing!'

'Sometimes my mind played games with me where I would get a twinge of pain and worry the reta had triggered kidney failure,' she says. 'I'm a bit dramatic like that, but I loved watching the numbers dropping on the scales too much to let it bother me.'

By the time she was coming close to finishing her first pen, Sally noticed her old appetite levels had started to creep back, and her weight loss was slowing down, so when purchasing a second pen, she increased her weekly dose to 3mg and then 4mg.

That was clearly a mistake.

'The dose was too much for me,' she says. 'All the familiar Mounjaro side-effects kicked back in and I felt sick all day every day from the moment I woke up in the morning to the moment I went to sleep. I tried everything to get rid of the nausea but it was relentless. Some days I had to work from my bed because I felt so ill.

'I persevered for three more weeks but in the end I had to give up.'

Sally lost 9lbs in nearly three months on reta. Then she stopped and regained 7lbs in a month. Still, she's adamant she'd go back to reta rather than Mounjaro when she can afford to do so – this time sticking to a lower 2mg dose.

One of the reasons the idea of injecting yourself with an unlicensed drug has become so popular among middle-class women like me and Sally is because, in the last six months, the buying and trying of reta has become completely 'normalised' not only on social media but in certain circles in real life too. 'Reta' has become something of a buzzword at the gym, for example.

Dr Luke Turnock, a senior lecturer in criminology at the University of Lincoln who monitors illegal drug sales, tells me retatrutide was the most listed GLP-1 on the illicit market back in 2024 – and its popularity is growing alarmingly fast.

He and his team of criminologists have traced the use of reta in the body-building community, where – alongside anabolic steroids and testosterone – weightlifters began using it to help strip body fat and boost performance.

From there it has entered the mainstream. When I quizzed my muscle-pumped 23-year-old son about this, he confirmed: 'Yes! Loads of my buddies have spoken about it and quite a few are taking it at the gym.'

This process of 'normalisation' is the cause of much concern among academics.

Dr Turnock worked closely with fellow scientist Dr Luke Cox, a lecturer from the school of sport and exercise science at Swansea University, on a study published in April this year highlighting the crucial role played by social media and internet forums in boosting a false sense of confidence around fake reta.

There is a 'reliance on anecdotal expertise', says Dr Cox, which encourages the 'spread of misinformation, unsafe experimentation and exaggerated claims of efficacy'. His great concern is that social media influencers – funded by incentive payments through affiliate links to online shops – are expanding the popularity and perceived 'safeness' of reta into the mainstream.

'The rapid expansion of this market is scary,' says Dr Cox. 'It's like the Wild West.'

'Because it is not, yet, a prescription-only medicine [i.e. regulated by the MHRA],' says Dr Turnock, 'reta falls into the same grey area as other experimental peptides [short chains of amino acids that, for example, allegedly have an effect on muscle growth] in terms of legal enforcement.

'This means when warehouses full of reta pens are busted, sellers are not prosecuted as they might be if they were selling tirzepatide or semaglutide [the active ingredients in Mounjaro and Ozempic].'

More worrying still, no one is yet certain that reta is safe.

As part of the GLP family of weight-loss drugs, it's expected to trigger similar gastrointestinal side effects – nausea, diarrhoea and constipation – as Ozempic and Mounjaro, as well as a similar risk of pancreatitis and gallbladder disease in extreme cases.

In fact, the early trials indicate reta might be more likely to trigger gastrointestinal side-effects than Mounjaro, depending on dose.

But there are additional concerns about elevated heart rate, particularly in those who take higher doses. Dr Cox says it's a frequently cited side effect, with fitness enthusiasts reporting that their wrist monitors pick up a resting heart rate ten to 15 beats higher than normal.

On an online forum of reta users, one member said: 'I had to stop taking reta because of heart palpitations and severe anxiety/panic attacks. I couldn't deal with the anxiety any more.'

Another agreed: 'Exactly what you said. Severe anxiety, panic attacks, inability to sleep, just intense anxiety which gives you a feeling of doom and that you're going to die.

'The first time it happened, I thought I was dying and called an ambulance, kept waiting to die in the ambulance and it never happened.'

Facebook support groups are also peppered with posts from young women discussing alarming changes to monthly cycles, such as 'my periods are all over the place' and 'I am on week 6 of reta and I have bled for 4 weeks'.

Others highlight skin issues, including 'my body was so itchy last night I couldn't sleep', 'across the bottom of my back is worse for me – it feels like sunburn' and 'mine was so sensitive even clothes touching hurt'.

A major issue here is the uncertainty over effective and safe dosages. One of the purposes of the phase three clinical trials is to investigate dosage – but until the drug is properly licensed, and regulated, users have to rely on anecdotal advice from online forums.

Too little reta and the jab is unlikely to work, but too much and you put yourself at risk of horrible side-effects – as Sally found out.

And when you are buying a drug on the black or grey market, you simply can't be sure whether the clear liquid is what it purports to be, or what concentration and potency it has.

When unlicensed reta first appeared, it was only available as a powder to be mixed with sterilised water that users would draw up in a disposable syringe. The drug is more stable in powdered form, and easier to transport from factories on the other side of the world.

This was acceptable to the body-building community, which had become familiar with the idea of making up peptide solutions to promote muscle growth – often from a vial of powder and using the sort of needles you'd pick up at a drug addicts' needle exchange.

That sort of alchemy strays too far into junkie territory for most middle-class sensibilities, so for a little more money, producers have begun making pre-filled reta pens which look and work just like the Mounjaro pens you get from an online pharmacy and deliver a measured dose through a very short, fine needle. The reta pens I found online looked reassuringly legitimate in their branded boxes sealed in cellophane.

But even if the pen does contain a solution of reta, there's no way of knowing how strong that particular solution is, or whether it's been stored in a refrigerated facility – if it's not, the peptides will become less effective.

Luckily some people posting on reta forums are talking sense. One helpfully warns: 'There's a lot of fake stuff on the market, fake labs, and a lot of pens sit in unrefrigerated warehouses for weeks or months on end so the peptide breaks down and degrades.'

This lack of consistency in the product can lead to a dangerous pattern where users think they're getting no effect from a 2.5mg shot (which could, in fact, be considerably weaker than that) so up their dose when they get their next pen. If that one is a full-strength pen, they risk overdose and can find themselves completely floored – even hospitalised – by side-effects.

'Regulatory bodies really do need to step in,' says Dr Cox. 'And why are social media platforms not filtering these targeted influencer posts and applying some sort of censorship to stop them proliferating via AI?'

Like many women frustrated by midlife weight gain, I've found myself easily seduced by the pressure from social media. But I'm not going to risk rolling the dice with my health by trying reta. That kind of uncertainty is just too much for me.

Even though I've tried a few dubious and probably ill-advised cost-cutting tricks during my Mounjaro journey, I'm happy to wait until this particular Godzilla of skinny jabs has passed all the necessary checks and can be dispensed legally by a proper pharmacy. And all the medical experts would unanimously agree with me.

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