Between 39,000 and 47,000 hospital outpatient appointments are missed every month, according to new figures.
The details were revealed by the HSE in a response to a parliamentary question tabled by Independent Ireland TD Ken O'Flynn.
Mr O’Flynn said the figures showed that more than half a million outpatient appointments were missed every year and he said this meant that the health service was "failing patients in plain sight".
"Half a million missed appointments every year. At the same time, patients are stuck on waiting lists. That is not bad luck. That is a system out of control.
"You cannot run a health service like this. Doctors are ready. Clinics are open. Patients are waiting. Yet appointments are being lost at scale," Mr O’Flynn said.
He said the failure goes beyond attendance and points to a deeper breakdown in management.
"I asked for weekly data by hospital. I did not get it. What I got was broad monthly figures that hide where the real problems are.
"That tells you something. The system is not being tracked in a way that allows it to be fixed," he added.
Mr O’Flynn has now requested further details from the Minister for Health on the cost of missed appointments, their impact on waiting lists, and what action is being taken to stop the losses.
