The wait for out-of-stock medicines can cause "extreme distress" in some patients and even see them admitted to hospital, pharmacists have warned.
A range of medicines, including drugs to treat early-stage breast cancer, depression and obesity, can be difficult for pharmacies to get ahold of due to supply chain issues.
It means patients can face worrying delays getting the drugs they need.
One pharmacist reported that a patient had panic attacks waiting for an antidepressant, while another said the wait for a breast cancer drug had caused "extreme distress."
In another case, a shortage of the blood clot drug Plavix had resulted in a hospital admission, it was claimed.
Nearly 90 percent of those who took part in the survey — published by the Chemist & Druggist Web site — said they were "very concerned" about difficulties they were having getting ahold of some medicines.
Roger Odd, a trustee of the Patients' Association, said, "There are 50 or more medicines that have been out of stock, it's unbelievable. It can't be right for patients to be suffering like this."