People taking weight-loss injections from unregulated sources are facing "serious consequences" for their health, it has been warned.
Stormont's Department of Health said there has been a rise in demand for drugs from unverified sources, and is investigating "falsified injectable weight loss pens" being circulated in the north.
A probe by the department's Medicines Regulatory Group (MRG) remains ongoing, and a number of the pens have been removed from circulation.
It found "fake medication" was being used that "presents a real risk of adverse health effects".
The items contain the drug semaglutide, which is approved for managing diabetes, but can also be used under guidance from a medical professional to help patients lose weight.
However, the pre-filled pens are only legally available on prescription, and those selling them on websites and in person can face legal consequences.
The department's senior medicines enforcement officer, Peter Moore, said: "You may be breaking the law by advertising or unlawfully supplying prescription-only medicines outside the legitimate supply chain. I would urge people not to source their prescription medication from unregulated sources."
He added: “We continue to monitor the marketplace and will take effective action where this is necessary."
MRG head, Canice Ward, urged people only to take prescription medicines after consultation with GPs, pharmacists and healthcare professionals "who have access to patient health records and can consider the risks and benefits associated with every medicine".
"The risk to the public due to illegal, falsified, or counterfeit medicines is very real,” she said.
"The public can be assured that the department is committed to and continues to take all possible steps to stop their illegal supply or misuse, and to taking strong action where wrongdoing is identified."
Suspected falsified medicines can be reported on the Medicines and Healthcare Products Regulatory Agency's Yellow Card system online at https://yellowcard.mhra.gov.uk/.
Referrals can also be made to the Department of Health's Medicines Regulatory Group by emailing counterfeit.mrg@health-ni.gov.uk.
