The woman, from South Leitrim, was recently brought to the hospital in an ambulance after seeking medical assistance.
However, upon arrival, she was made wait in the ambulance for six hours as there was no space inside the accident and emergency department.
Sligo Leitrim TD Martin Kenny raised the incident in the Dáil and said Sligo University Hospital was recently described as one of the most overcrowded hospitals in the country.
He said he was recently informed that the ambulance service was at one stage notified not to bring patients to the hospital, such was the overcrowding in the accident and emergency department.
Speaking in the Dáil, the Sinn Féin TD said, "It is the same all over the country.
"In one case I had recently, a woman waited outside Sligo hospital in an ambulance for six hours because there was no space to bring her into the hospital.
"That ambulance came from South Leitrim.
"During the time the ambulance was waiting, there was no ambulance cover in the region.
"That is happening everywhere all over the place.
"It is small wonder, therefore, that people feel the service is so poor in the public system that they need to get insurance to be able to have a service provided," said Deputy Kenny.
The issue was raised in the Dáil during a debate on the Health Insurance (Amendment) Bill 2025.
Deputy Kenny said almost 50pc of the population have health insurance and in some cases, "the level of service they get is often not up to the standard they would expect."
He called for a review of how the health service in the country works.
"Having health insurance does not solve the problem for a lot of people.
"In fact, all it does is make them pay more and still get an inadequate service.
"There needs to be a full review of how our system works.
"I know SláinteCare was supposed to do that, but it has not delivered.
"There needs to be a re-examination of what we are going to do to get a proper health system in place that provides adequate services for all of our citizens," said Deputy Kenny.