44 percent of doctors surgeries are turning away new patients.
A survey of 336 GP practices by the Sunday Independent's found 148 are operating at full capacity.
The survey found rural areas in the south west and Dublin commuter belt counties to be worst affected.
The problem was particularly evident in Co Laois, where no surgeries were found to have space for new patients.
80 percent of those in Carlow and Longford were also found to be at full capacity.
In Kilkenny, 75 percent said they were full, with the rest stating an assessment of new patients was needed before a decision was made.
Other counties that ranked high on the list included Tipperary at 54 percent max capacity, Kerry at 53 percent and Limerick at 52 percent.