The Medicines and Healthcare products Regulatory Agency is warning people not to risk their health by misusing prescription weight-loss medicines or buying fake products online during the summer.
The regulator said prescription weight-loss medicines are being advertised illegally on social media alongside quick-fix slimming claims. It urged people prescribed GLP-1 medicines not to increase their dose in an attempt to lose weight more quickly.
Semaglutide, sold as Wegovy, tirzepatide, sold as Mounjaro, and liraglutide, sold as Saxenda, should be taken only as prescribed by a healthcare professional. The MHRA said patients should use them alongside a healthy diet and fitness regime.
The agency warned people not to buy weight-loss medicines from unregulated websites or social media sellers. It said authorised GLP-1 medicines in the UK have only been shown to be safe and effective for people with a body mass index of 27 or more.
The MHRA also warned against online promotion of retatrutide, saying it has not been authorised for use in the UK and anyone selling it is doing so illegally. It said fake medicines may contain different ingredients or be contaminated with harmful substances.
People making diet changes were also advised to check whether foods or fasting could affect their medicines. The MHRA cited grapefruit with simvastatin, and said some medicines, including metformin and naproxen, should be taken with food.