Hundreds of people have taken part in a rally outside Our Lady's Hospital in Navan, Co Meath, as part of a national day of action.
The Save Navan Hospital campaign has been fighting proposed plans to replace the emergency department there with a 24-hour medical assessment unit.
That plan has yet to be implemented.
Before Christmas, a new ambulance bypass protocol was introduced whereby critically ill or unstable patients being transported by ambulance would no longer be taken to the emergency department at Navan and would instead be brought to other hospitals.
The Chairperson of the Save Navan Hospital Campaign said the day of action was an unprecedented response to an unprecedented hospital overcrowding crisis.
Aontú TD Peadar Tóibín said the HSE and the Government "can't seem to draw the dots between the capacity crisis in A&Es and their insistence on closing A&Es like Navan".
Mr Toibin said that doing this creates pressure on other hospitals, and he demanded that the HSE and Minister for Health invested in front line services like Navan, to ease that pressure elsewhere.
"We need investment in the likes of Navan A&E, not closure," he said.
Local Sinn Féin TD Johnny Guirke said that people were concerned when they see what has happened in Limerick.
Thousands of people also gathered in Limerick city centre to take part in a march over continued overcrowding at University Hospital Limerick.
"We don't want that happening here, we want to protect and enhance services here," he said.
"When we see what's happening in UHL, the closed EDs in Nenagh and Ennis and the chaos that happened there. We don't want Meath people being put at risk by bypassing the hospital.
"We need investment in services here."
Read more: Thousands protest in Limerick over hospital overcrowding
Local woman Eileen Coleman said a situation where people would have to go the ED in Drogheda was "ridiculous" and that there should be more investment in the hospital.
"It saved my life. I had a heart attack some years ago, and if it wasn't there I'd be dead now," she said.
Another woman, Deirdre Butler from Kells, said the plan to replace the emergency department would be a "total disaster".
"There's no way we can let this hospital go," she said.
This week the Ireland East Hospital Group, which runs Our Lady's Hospital, said that the ED at Navan "remains open with no plans for closure".
Last month, a new ambulance bypass protocol to divert ambulances carrying critical and unstable patients away from Our Lady's Hospital Navan Hospital was put in place.
Previously, Navan was already being bypassed for stroke, trauma, cardiac arrest, paediatrics and obstetrics patients.
The new protocol means that now, other critically unwell and unstable patients being transported by ambulance are also being transferred to other hospitals, like Our Lady of Lourdes in Drogheda and the Midland Regional Hospital in Mullingar.
The updated ambulance bypass protocol was agreed by the Minister for Health and the HSE, to address what the HSE called "urgent patient safety matters for the small number of patients presenting in ambulances to Navan who are critically or seriously unwell or likely to deteriorate".
In December, the HSE said that no agreement had been reached with Minister for Health Stephen Donnelly on the reconfiguration of the emergency department at Navan to a 24-hour medical assessment unit, or on a full ambulance protocol.
The HSE said it had submitted a capacity review to the Minister, which remains under consideration by Minister Donnelly and government.