The study is being run through the MHRA’s Yellow Card scheme, which allows anyone to report an issue with a medicine, vaccine or medical device to help identify safety issues as early as possible.
Patients aged 18 and over, with bad reactions to the weight loss jabs – which are also licensed for type 2 diabetes – are being asked to report the detail on the Yellow Card website.
They will then be asked if they would be willing to take part in the study, which will check whether some people are at a higher genetic risk of acute pancreatitis when taking these medicines.
Patients will be asked to submit more information and a saliva sample, with the overall aim of reducing the occurrence of the side effects in future, says the MHRA.
Cases recorded on the Yellow Card website up until 13 May this year include 10 in which patients, who were using weight loss drugs, died from the effects of pancreatitis – but it is not clear whether other factors also played a part.
It is impossible to know exactly how many people in the UK are on weight loss drugs as many users obtain them online through unregulated sources, rather than through their doctors.
Health officials have suggested the jabs could help turn the tide on obesity. However, they have also warned the drugs are not a silver bullet and often come with side effects, commonly including nausea, constipation and diarrhoea.
And the MHRA has also warned that Mounjaro could make the oral contraceptive pill less effective for some patients.