MHRA raids UK's first illicit weight-loss injection factory

On 24 October 2025 the MHRA announced that it had dismantled what it described as the first illicit weight-loss injection factory ever found in the UK. It was a warehouse on an industrial estate outside Northampton, and more than 2,000 filled retatrutide and tirzepatide pens were waiting to be sent out.^[1]

What was announced

The MHRA's Criminal Enforcement Unit raided the site over three days. Inside they found not just stock but a production line: empty injector pens in their tens of thousands, the chemicals to fill them, and the packaging to make them look finished.^[1]

The pens were labelled as retatrutide and tirzepatide. Tirzepatide is the active ingredient in Mounjaro, a licensed medicine.^[3] Retatrutide is not licensed anywhere. The MHRA said plainly that retatrutide "has not been approved for UK use" and that any product sold in the UK claiming to contain it is likely to be illegal and potentially dangerous to health.^[1][2]

What is new

According to the MHRA, this was the first time an illicit production facility for weight-loss injections had been found in the UK.^[1] It showed that some of the pens being sold in group chats and on social media were being assembled and filled in a warehouse, by people with no licence, using equipment and ingredients of unknown origin.

It also confirmed that "retatrutide" had become a product line for illegal producers well before the drug had finished its trials. At the time of the raid, no Phase 3 result had been published. The first, TRIUMPH-4, came seven weeks later.

What it does not mean

• It does not mean every pen sold online came from this warehouse. Products reach the UK from many sources, and the MHRA has since found a second site.
• It does not tell you what any particular pen contains. Being made without a licence means no sterility testing, no strength testing and no traceability, so the contents of any one pen are simply unknown. The testing page collects what independent labs have found.
• It does not make having a pen a crime. UK medicines law targets the people who make, sell and supply unlicensed medicines, not the people who end up with them. See is it legal in the UK?

Context

The MHRA had already warned in 2023 about counterfeit weight-loss pens that turned out to contain insulin, sending people to hospital with dangerously low blood sugar.^[4] The counterfeit pens page covers those cases. This raid added a new category: pens that are not fakes of a licensed brand, but unlicensed products of a drug that has no licensed version at all.

The running summary of every UK seizure is on the MHRA enforcement page.