A diabetic is struggling to get the medicine he needs to manage his blood sugar due to a shortage.
John Hallam, 82, was told by his pharmacy that Ozempic would not be available until January 2024.
It is part of a group of drugs recently popular with celebrities using it as a weight loss aid.
Diabetes UK is urging clinicians not to prescribe the drugs outside of approved use until the shortage is forecast to end early next year.
Mr Hallam, from Lincoln, has had type 2 diabetes for 33 years and said Ozempic was “vital and very beneficial” to him.
He was prescribed an alternative drug but said it did not work as well and caused his blood sugar to spike, which can lead to a stroke or sight problems.
“I feel very annoyed and frustrated that people can buy it privately and are denying people who rely on it,” he told the BBC.
GP David Sheehan, diabetes lead at Nettleham Medical Practice in Lincoln, said the group of drugs used to treat type 2 diabetes have become widespread among celebrities like Elon Musk, who has endorsed them as a weight loss aid.
They contain the ingredient semaglutide which can supress appetite.
Dr Sheenan said people getting private prescriptions of the drug were “causing problems for diabetes patients” who were being prescribed “less suitable” drugs such as insulin that can cause hypoglycemia.
“There is not enough left as the supply is being diverted. We’re calling for those using private prescriptions to wait until supply is back to normal,” he added.
Douglas Twenefour, head of care at Diabetes UK, said: “We understand that off-label prescribing can be beneficial in some circumstances, but we cannot support it when it is directly contributing to ongoing shortages for people living with type 2 diabetes and the impact this has on managing it well.”