Warnings issued as suspected fake weight-loss medicines surge fivefold in two years

Experts have warned that some users are becoming dependent on weight-loss injections.

Fake slimming drugs are said to be flooding Britain’s black market, with official reports of suspected illegal weight-loss medicines rising by 432 per cent over two years, according to newly released figures.

The problem may be even larger than the data suggest, as criminals exploit booming demand for blockbuster injections such as Mounjaro and Ozempic.

One particularly troubling trend is the sharp rise in reports involving retatrutide, an experimental weight-loss drug that is not approved for public use but is being promoted online as a powerful slimming treatment.

Records linked to the substance, sometimes sold under the name “RETA,” climbed from just nine in 2024 to 257 in the following year, an increase of more than 2,700 per cent.

Experts are also warning that some users are becoming fixated on the dramatic weight loss these drugs can produce, leaving them reliant on the injections and fearful of regaining weight, even though the medicines are not known to be addictive in the conventional sense.

The Medicines and Healthcare products Regulatory Agency (MHRA) held 756 records connected to suspected or confirmed fake and unauthorised weight-loss medicines in 2025, compared with 142 in 2023.

Those figures include reports and intelligence about suspected illegal weight-loss drugs logged by the MHRA, rather than confirmed counterfeiting cases.

One record could cover anything from a single suspect injection to thousands of fake slimming pens, so the numbers do not show how many illegal products are actually circulating.

The totals also only reflect suspected illegal activity that came to the watchdog’s attention or was uncovered by its investigators, meaning the true size of the black market remains unknown.

Counterfeit injections may contain the wrong ingredients, dangerously inaccurate doses or harmful contaminants, putting users at risk of serious illness and potentially life-threatening complications.

The findings come shortly after investigators seized more than 12,000 fake slimming pens worth £2million from a dirty Birmingham warehouse, along with packaging for another 30,000 products.

The seized items included injections marketed as retatrutide and tirzepatide, the active ingredient in Mounjaro.

The dangers are not merely theoretical.

Fake Ozempic and Saxenda injections have previously been found to contain insulin instead of the advertised medicines, and some patients were hospitalised after suffering dangerously low blood sugar.

That can lead to seizures, unconsciousness and, in severe cases, death.

In February, the MHRA also warned that counterfeit Mounjaro pens had been supplied through a UK online pharmacy, raising further concerns about safety and sterility.

The black market is thriving amid extraordinary demand.

Research published by University College London estimated that 1.6 million adults in Britain had used prescription weight-loss medicines over the previous year, while another 3.3 million were interested in trying them.

Yet although about 3.4 million people in England are eligible for Mounjaro under broader criteria, the initial NHS rollout is aimed at only around 220,000 patients over three years.

Many people are paying privately, while others may be tempted by cheaper injections sold through social media or unregulated websites.

The scale of the illegal trade has already led to major enforcement action.

More than 18,000 illegal and counterfeit weight-loss and diabetes medicines were seized at UK borders between January 2024 and June 2025, according to figures highlighted in a London Assembly report.

The new Freedom of Information figures, obtained by the UK Addiction Treatment Group (UKAT), also show a steep rise in records involving Mounjaro.

Those records increased from 24 in 2024 to 203 in the following year, almost a 750 per cent rise.

Semaglutide, the ingredient in Ozempic and Wegovy, accounted for 634 records across the three years, although its annual total fell slightly in the latest year.

The MHRA said its figures were not a definitive count of counterfeit medicines or affected patients, and that changes in recording practices could affect comparisons.

Zaheen Ahmed, head of therapy at UKAT, said: “These figures are a huge red flag, particularly the explosion in records involving retatrutide.

“It's being heavily promoted on social media as a fitness and weight-loss peptide, but people may not realise the risks of sourcing unregulated substances online.”

He added: “At UKAT, we've treated clients for weight-loss medication addiction for the first time ever this year.

“That's a worrying development and a reminder that these drugs should not be treated as risk-free shortcuts. We need greater awareness of the potential harms before more people find themselves struggling with the consequences.”

Dr Alison Cave, the MHRA's chief safety officer, said: “Patient safety is our top priority, and we work continuously to protect the public from illicit medicines and ensure people access medicines, including those used for weight loss, correctly and safely.

“We have seized thousands of fake weight-loss medicines worth approximately £2million and stopped them reaching the public.

“We are substantially increasing our criminal enforcement capacity, giving us more specialist resources to investigate, disrupt and, where appropriate, prosecute those involved in illegal medicine activity.”

She warned: “Obtaining medicines from illegal or unregulated sources may put your health at serious risk.

“There is no way of knowing what these products contain, whether they have been manufactured to appropriate quality standards, or how they have been prepared, transported or stored.”

Dr Cave added: “Retatrutide is still in clinical trials and has not yet been authorised for use anywhere in the world. Therefore, there is no way of accessing retatrutide safely outside of a clinical trial.

“There is only one safe way to obtain genuine weight-loss medicines: through a prescription issued by a qualified healthcare professional and dispensed by a registered pharmacy.”