An NHS receptionist has shed 4st using a DIY Mounjaro hack that’s sweeping social media – but experts warn it could put lives at risk.

Siobhan Jackson, 40, reduced her weight from 14st 1lb and a size 20 to just under 10st and a size 10–12 over 11 months by dividing her slimming injections into smaller, more frequent doses, deviating from the official guidelines.

The mother-of-two, from Kirby-in-Ashfield, Nottinghamshire, admits she knew the practice, dubbed ‘microdosing’, went against the rules but says she is far from alone.

‘In my experience people are not taking it as prescribed,’ she said. ‘I’m not the only one – lots of people are doing this.’

Jackson decided to try Mounjaro in March last year after years battling her weight and dangerously high blood pressure. 

At one stage her readings soared to 170/140 – far above the healthy 120/80 – and doctors had to triple her medication to bring it down.

‘I was relying on a cocktail of tablets and thought: I really need to do something to help myself,’ she said. ‘At the end of a stressful day I’d come home and have crisps and chocolate every night. It wasn’t good for me.’

She first lost 1st 7lb through diet and exercise, then turned to the jab after seeing success among patients collecting prescriptions at the GP surgery where she works.

An NHS receptionist has shed 4st using a DIY Mounjaro hack that’s sweeping social media – but experts warn it could put lives at risk

Siobhan Jackson, 40, slimmed from 14st 1lb and a size 20 to just under 10st and a size 10–12 in 11 months after splitting her slimming jabs into smaller, more frequent doses

She ordered her first pen privately online for around £100. The results were immediate. ‘I wasn’t hungry at all,’ she recalled. ‘Sometimes it got to 2pm and I was forcing myself to eat lunch.’

After reading Facebook groups discussing microdosing, she experimented by reducing her 7.5mg pen to 6.25mg and injecting twice weekly with 3.125mg.

‘For me, microdosing worked really well,’ she said. ‘My appetite was more stable and I could eat more consistently. I didn’t want to be losing half a stone in a week.’

Over the next year she steadily lost nearly four stone. She now plans to taper down and eventually stop altogether.

‘The plan had always been to stay on a very low dose and come down gradually,’ she said. ‘I haven’t got much more I want to lose.’

She believes the DIY method also saved her money. ‘Every time I had the chance to move up to the next pen I did, but I didn’t always increase the dose — there wasn’t the need.’

Jackson says the UK is too rigid compared with America, where she believes patients are given more freedom.

‘Here we’ve decided this is the dose, this is how you move up, and these are the maintenance doses,’ she said. ‘It’s not one-size-fits-all, but sometimes the NHS can’t be as bespoke as elsewhere.’

The Mounjaro microdosing trend comes after similar concerns were raised about Ozempic users.

Doctors told the Mail they are contacted ‘almost every week’ about the practice, but warned it is unsafe and unsupported by any UK clinical guidance.

NHS psychiatrist Dr Max Pemberton, who also runs a weight loss jab service, said: ‘There are real risks. You could inject too much or too little.

‘You could damage the drug in the process. And worst of all, it might give people a false sense of security – that what they’re doing is safer, when it really isn’t.

‘Absolutely no reputable prescriber would endorse this behaviour. It makes me incredibly worried that people are taking their dosage into their own hands. They’re risking their health every time they do so.’

Professor Alex Miras, an endocrinologist at Ulster University, added: ‘People are risking serious side effects from overdosing – as well as the potential to develop a life-threatening infection.

‘Pens can malfunction if used in ways they weren’t designed for, and once opened, they lose sterility. That means leftover liquid could introduce harmful bacteria. Don’t take the risk.’

The Medicines and Healthcare products Regulatory Agency (MHRA) said: ‘Patient safety is the MHRA’s top priority, and we closely monitor all medicines following authorisation, to ensure their benefits continue to outweigh any risks.

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‘People should follow the dosing directions provided by their healthcare provider when prescribed weight-loss medicines, and use as directed in the patient information leaflet. Medicines are approved according to strict dosage guidelines.

‘Failure to adhere with these guidelines could harm your health or cause personal injury.

‘If you have any concerns about a medicine you are taking, please seek advice from your healthcare professional.’

Despite the warnings, Jackson insists she has no regrets. ‘Had it not been for the groups I wouldn’t have been as comfortable microdosing,’ she said. ‘But it worked for me – and I know I’m not the only one.’