Forget Mounjaro – I’m on ‘reta’, the Godzilla of weight-loss shots. Here’s everything I’ve learned so far…

Two months ago, an unremarkable-looking jiffy landed in my mailbox. With my heart racing, I snatched it and stashed it secretly away, I wanted to be alone in the house to open what I knew was inside.

Looking back, it’s hardly surprising I felt the need to be so furtive. This was my first delivery of retatrutide – or ‘reta’ as it’s more commonly known – the triple-action peptide drug that’s been hailed the Godzilla of all fat drugs.

And as I pulled out a baffling array of contents with hands trembling, I was feeling totally out of my depth. Spread across my kitchen island were vials, syringes, scarily long needles but – alarmingly – not one single instruction on how to cobble it all together.

Welcome to the Wild West of unregulated and illegally supplied weight-loss drugs that have flooded social media in recent months in response to the huge price hike of injections like Mounjaro and Wegovy. 

And particularly murky is that what’s being supplied – reta – is yet to be approved by the US Food and Drug Administration (FDA), and therefore has yet to be judged officially safe to take.

I’d bought my guilty stash from a stranger who called himself Jim Slim on WhatsApp. He’d bought his, probably in bulk, from an industrial-scale Chinese laboratory.

While what Jim Slim was doing is strictly illegal, I was operating in a grayer area. And, as a 55-year-old, middle-class mother-of-four, it’s no exaggeration to say I had just crossed the line to a very dark side of dieting.

If I could actually figure out how to inject myself with the single most powerful weight-loss solution ever produced, I’d very probably be taking part in the largest unsupervised drug experiment in modern history.

Yes. Quite honestly, I don’t know what I was thinking either…

It’s not even as if desperate times called for desperate measures. I’d already been on Mounjaro since February 2025 and it had worked brilliantly for me.

Last year, I lost 42lbs in six months with no side effects at all. At 5ft 7in and a starting point of 173lbs (78.5kg) I’d successfully reached my target weight of 132lbs (60kg) by July, with minimal effort.

The souped-up, turbo-charged weight-loss effects of reta – in clinical trials the best drug yet discovered for suppressing appetite and shedding pounds – wasn’t what motivated me. In common with many other women, it was the cost.

In the US, monthly Mounjaro may cost some patients up to $1,100 per month and some people may have seen their out-of-pocket costs for the GLP-1 increase as health insurers cut back on their coverage of weight-loss drugs.

My cost increased from about $200 per month to $406.

Strictly speaking, even this shouldn’t really have been an issue as I was already easing off my dose, having reached a point on the scales not seen since my wedding dress fitting in 1999. 

But the problem with all these weight-loss drugs is that there is no real exit strategy. The pounds plummet, your self-esteem rockets and before you know it, you’ll do almost anything to stay skinny.

Like so many other women who have had similar triumphs on Mounjaro, it’s hard to let go after you’ve reached your target. Particularly as the hunger I felt when the drug left my body was so intense, I started channelling Henry VIII scoffing himself silly at a medieval banquet.

The next step? The ‘microdose’. For the last eight months, I have kept a stockpile of Mounjaro pens in the fridge as a comfort blanket, eking out tiny amounts whenever my food cravings consume me.

And this seems to have worked too. My weight has been consistently fluctuating between 128lbs (58kg) and 134lbs (61kg) with a BMI of 20 (the healthy range is 18.5-24.9). Along with these intermittent Mounjaro doses, I have also taken up running. So far, so good.

But then came another blow – a crackdown on my supply of the legal stuff. The online pharmacy where I’ve always bought my Mounjaro – pretty much no questions asked – recently began paying more attention to my orders. They demanded actual video calls to see me standing on the scales.

They became annoyingly tricky about agreeing to send me pens, telling me: ‘You don’t need this much Mounjaro any more, you’ve reached your target weight.’ Which obviously is responsible on their part, but felt, quite frankly, a bit like abandonment to me.

I must have sent them nearly $5,400 in the last 17 months. Couldn’t they just turn a blind eye?

I know, I know, but I say all this in a vain attempt to excuse the idiocy of what happened next. A casual exchange with a friend of a friend this June led me to the dodgy doorstep of reta.

‘Everybody’s on it,’ she said. ‘I was buying mine under the counter from a “peptide shop” in Barking. But I’ve found a cheaper dealer now on WhatsApp. Do you want his number?’

This, from a woman whose job it is to manage investment portfolios for the wealthy. It didn’t look, or feel, like drug dealing. So, of course, I took Jim Slim’s number and messaged him.

He replied almost immediately explaining (sort of) how things work. I would start on a 2mg dose, before ‘titrating’ every four weeks up the ladder, gradually increasing the strength to minimize side effects.

He would send me a vial of retatrutide powder, which I would carefully mix with something called ‘bac’ water – a sterile solution that prevents bacteria growing in the vial of reta, (which you’ll be keeping in your fridge for at least four weeks).

Frankly it all sounded like a lot of faff, but I’d be saving myself a fortune. Four weeks on reta was going to cost just $176.

I went online and did some research. Like Wegovy and Mounjaro, reta is also a synthetic peptide. It’s being developed by Eli Lilly, the same company that makes Mounjaro. It’s still in clinical trials and so can’t be legally prescribed but it has a superpower the others don’t have.

Often called ‘Triple G’ it activates not only GLP-1 (which is what Ozempic and Wegovy do) and a second peptide called GIP (which is what Mounjaro does) but it also targets glucagon receptors, all three together influence appetite, blood sugar and energy use.

In clinical trials, the highest studied dose led to a mean weight reduction of 28.7 percent at 68 weeks, the largest average loss reported for a weight-loss medicine to date.

Jim Slim, as I now know, is one of thousands of ‘grey market’ sellers operating in this murky world that sits outside medical regulation. Reta vials are sold across TikTok and Reddit platforms, usually labeled ‘for research use only’ as a way to get around the law. Buying them isn’t explicitly illegal but anyone selling them as a weight-loss injection or injectable supplement is committing a crime.

Which might explain why, when I started asking boring questions such as, ‘Where did you get this from and how do you know what’s in it?’ Jim Slim refused to type an answer, instead, asking if he could call.

Over the phone he sounded – how can I say? – not exactly like a plumber or electrician but not far from it. He joked that there wasn’t a check-a-trade site where I could go for references but he had dozens of happy clients and could provide before and after photos.

His reta had 99 percent purity, he insisted, and he could prove this by providing me with a certificate of analysis (COA). I now know that these COAs from non accredited labs aren’t worth the paper they’re written on, but there was no way of me finding who his supplier lab was as he certainly wasn’t going to tell me.

It’s hard to justify the total lapse in good sense – not to mention the illogical leap of faith – I must have had to place that first order. All I can say is that I know plenty of perfectly sane women just like me who have done the same and suffered no ill effects which reassured me.

On the other hand, you could say it’s hard to justify not doing it – based on the financial savings alone.

There’s a huge downside though, and that is the fact you’re left to figure everything out for yourself. I suppose this serves me right for stepping outside the supported, ‘safe’ world of regulated weight-loss jabs. Nobody told me I had to be good at maths – I failed my O-level, which is a worry, because to understand reta, you have to understand measurements. For someone who doesn’t know her milligrams from her millilitres, this feels foolhardy.

Also Mounjaro is prescribed by strength and reta works on volume. Nobody told me this either. All I had to do with Mounjaro was inject an already calculated dosage in a pen. Taking reta requires nothing short of an unsupervised science experiment in my Ikea kitchen. Science, for the record, is something else I failed at school.

The challenge is that you have to carefully add an exact quantity of ‘bac’ water. You do this with a syringe they provide but it’s tricky and if you get it wrong it affects the strength of the dose. Then you use a different needle (also provided) which, frankly, looks like some kind of Victorian torture implement, to stick this combined dose into your stomach. Fun times.

So how does it feel?

I’m not exaggerating when I say you really know there’s a drug in your system. On Mounjaro the only thing I experienced was a welcome lack of hunger and occasional constipation. But from the offset with reta, I felt the kind of overwhelming fatigue you get in the early days of pregnancy.

I had to take my daughter Dolly, 17, to a university interview and just couldn’t drag myself into the college, opting instead to lie across the back seats of the car and have a snooze.

I’ve been on reta for eight weeks now and every morning after a restless night with intense dreams, I wake with a mouth drier than a cream cracker in the desert. This intense dehydration lasts all day. The upside is that, like Mounjaro, I don’t feel remotely hungry. Mostly, I have to force myself to eat – usually chicken, salmon or something else with high protein.

Much more concerningly – and I can’t say this is definitively linked – during the first month of taking reta, I experienced a chronic pain in the left side of my stomach. I ignored it for two days while it got worse until, one night, I couldn’t bear it any longer and went to the emergency department in the middle of the night – only to be diagnosed with suspected diverticulitis (a common condition where small pouches, called diverticula, form and push outward through weak spots in the walls of the colon).

Obviously, I had to tell them what I was taking and there followed much eye-rolling and a definite shift in bedside manner. In fact, as the doctor walked away from me, I heard him say to his colleague: ‘I’m just going to treat her like she’s a ketamine addict. She’s choosing to put her body at unnecessary risk.’ I couldn’t really argue with that.

He prescribed me antibiotics but was openly disapproving. My daughter, who is a student paramedic, tells me that if anyone calls with stomach pains one of the first questions they now have to ask is, ‘Are you on weight-loss drugs?’ This wasn’t part of the training a year ago.

And the medical profession are not the only ones to hold this view. My husband, Keith, thinks I’ve gone completely mad and constantly tells me I’m too skinny.

In fact everybody tells me I’m too skinny. But I don’t care. I’m loving it. I’m also prepared to do almost anything to stay this way.

If that sounds irresponsible and selfish then consider this. I have never once taken drugs or anything stronger than an antibiotic. I’ve never taken the contraceptive pill, and I even swerved HRT because – until now – I’ve always been nervous about putting drugs of any kind into my body.

And so more than anyone I understand the absurdity of what I’m doing. Injecting reta seems even more bonkers because there’s no denying, not even to myself, that I’m throwing all caution to the wind to keep the weight off.

Maybe other women will understand. When you’ve spent decades feeling frumpy, ignored and depressed because nothing looks good on you, having a body you’re finally proud to show off feels like an incredible gift.

This might seem shallow, but it’s about so much more than a pointer on the scales. The knock-on effect has been life-changing. I feel happier than I have in years. In fact, I’m having a complete renaissance, which I know is common for post-menopausal women in their 50s anyway, but for me, the catalyst has most definitely been getting thinner.

I’m still on the lowest dose because the side effects are extreme. Tiredness subsides over the week but the first few days after injecting it’s difficult to function normally. I haven’t lost weight but haven’t gained either.

I just want to plateau, so my plan is working. I’ve got three more weeks on the current dose and will probably order the same again from Jim Slim.

It might seem odd to be taking such a huge risk simply not to gain weight, but honestly, for me, it’s worth it.

Phase three trials of reta are currently testing the drug for safety and effectiveness. Eli Lilly plans to apply for official review with health regulators in early 2027, at which point it will then be approved – or not – for legal use as a weight-loss drug.

Best case scenario is that, if approved, the cost of reta will undoubtedly shoot up and I’ll either have to find a way to afford it or another way to maintain my weight.

The worst case scenario is that it won’t get approved because they’ll make some gruesome discovery that everybody who has taken it so far is in deep trouble.

Would I care? Possibly not, if I’m still in my size 10 jeans.

Why you mustn’t try this at home

By Dr Jack Mosley, author of Food Noise

It was Ozempic that first dominated the headlines, and for good reason. After one year on the injection (originally developed to treat type 2 diabetes), people were losing 15 percent of their body weight according to the studies. Ozempic semaglutide acts on one receptor: the GLP-1 receptor. Then there was Mounjaro tirzepatide. Dubbed the ‘King Kong’ of weight loss medications, this could lead to 20 percent body weight loss in those living with obesity. Mounjaro acted on two receptors: GLP-1 and another called GIP.

Now there’s retatrutide which acts on three receptors (the GLP-1, the GIP and the glucagon receptor) and can lead to even greater weight loss, comparable to bariatric surgery. But retatrutide is not yet approved yet and is unlikely to receive full regulatory approval until 2027. And yet, it has been available in shady corners of the internet for months if not years.

The black market for GLP-1s is booming. You can buy illicit copies of retatrutide from gyms, beauticians, even from TikTok.

Some people selling these medications are exploiting a gray area in regulation by selling them as ‘research chemicals’ which are ‘not for human consumption’, whilst at the same time giving instructions on how to inject them.

If you are buying retatrutide at this point in 2026, you are buying an unlicensed and potentially dangerous version of the medication.

You may be getting the wrong dose, a different version of the drug or in fact a different medication entirely. The outcome could range from receiving no products and being outright scammed, to receiving the real product at unknown concentrations, potentially with impurities or even dangerous bacteria.

There have also been multiple reports of people being hospitalized after injecting themselves with insulin sold as GLP-1s. Others have been struck down by serious infections.

These counterfeit versions are dangerous. You really have no idea what you are putting in your body. Many of them are manufactured illegally in China, India and Russia.

So, if you are buying these medications via unregulated, illicit sources, you really are playing Russian roulette with your health.

Dr Jack Mosley is the author of Food Noise (Short Books, $5)