The UK medicines regulator has issued a public warning about fake and potentially harmful weight loss pens after seizing hundreds of devices sold by illegal traders. The pens, with which the traders’ drugs are injected, are claimed to contain the medications Ozempic (semaglutide) or Saxenda (liraglutide), which are used for weight loss. However, these pens are thought to contain other substances. A small number of people who have been hospitalised after using the pens have experienced serious side-effects ranging from hypoglycaemic shock to coma, leading health officials to suspect the pens contain insulin. This week Austrian authorities said several people had gone to hospital after injecting counterfeit Ozempic. The Medicines and Healthcare products Regulatory Agency (MHRA) urged the public not to buy any pre-filled pens claiming to contain Saxenda or Ozempic, and to consult a healthcare professional qualified to prescribe medicines and obtain a prescription. “Buying products such as Ozempic or Saxenda without a prescription, from illegally trading suppliers, significantly increases the risk of receiving something which is either fake or not licensed for use in the UK,” said Dr Alison Cave, the chief safety officer at the MHRA. Since the beginning of the year, the medicines regulator has seized 369 potentially fake Ozempic pens and has had reports of fake Saxenda pens from members of the public who obtained them through non-legitimate routes, such as unregulated websites, without a proper prescription. Prior to 2023, the regulator had not seized any fake weight loss pens. The products fail to meet strict quality and safety standards, so people using them could put their health at “significant risk”, Cave said. “We are advising all members of the public not to use any pre-filled weight loss pens they may have bought online and instead report it to us so we can investigate and take any necessary action.” Semaglutide and liraglutide are known as GLP-1 receptor agonists and are used to treat type 2 diabetes and help manage body weight. They are available as injections, often referred to as pens or jabs. Saxenda is authorised in the UK for use for weight loss, together with diet and exercise. Ozempic has been authorised for the treatment of adults with type 2 diabetes, also with diet and exercise. While it is not authorised for weight loss in the UK, Ozempic is commonly used off-label for that purpose. Prof Paul Gately, the chief executive of Obesity UK, said the charity was “very concerned” to hear that people living with obesity were falling victim to criminals obtaining and selling fake weight loss drugs. “The dangers to health are clear,” he said. The UK health minister Will Quince said fraudsters selling hidden market medicines were extremely dangerous and they put people’s health at risk. “The medical advice is clear – patients should only use medicines like Ozempic or Saxenda where they’ve been prescribed it by a legitimate source such as their GP or another legitimate prescriber. The MHRA have our full support in cracking down on these illegal online suppliers to ensure that patients are protected,” Quince said. Cave said anyone who suspects they have side-effects from semaglutide, liraglutide or any other medicine, or suspects that they have used a fake product, could report it to the MHRA’s Yellow Card scheme.