The Health Products Regulatory Authority (HPRA) has said that 254 units of falsified Semaglutide have been detained in Ireland so far this year.
The drug is used to treat Type 2 diabetes and in some cases off-license for weight loss.
Off-license means that the drug is used for a different illness that is stated on the drug license.
The authority has warned of the serious health risks associated with sourcing prescription medicines online.
It said there has been a significant increase in the detention of products labelled as containing Semaglutide, up on the 32 units detained last year.
The products detained included vials of white powder, or clear liquid labelled as containing the drug and presented as a generic version of the product.
The HPRA said there is no authorised version of Semaglutide in powder form or generic form and any product of this nature promoted online is falsified.
Semaglutide is the active substance used in medicines such as Ozempic, Rybelsus and Wegovy.
HPRA Director of Compliance Grainne Power said the products detained included generic versions of pens and were all falsified medicines.
She said there is no way to know what the products contain, or the strength of any dose and they could pose a serious health risk.
Separately, on 18 October last, the European Medicines Agency issued an alert relating to pre-filled pens falsely labelled as the diabetes medicine Ozempic identified at wholesalers in Austria, Germany and the UK.
The HPRA said that these pens have not been detected on the Irish market at this time and are not part of today's alert.
