Up to 100,000 people could lose their medical card under the governments plan to cut €666m from the Department of Health.
Some €113m of the cuts are to come from a controversial tightening of the medical card scheme.
Health Minister James Reilly said that the cuts are the largest and most challenging ever faced by his department.
An economist at University College Cork, Seamus Coffey, has warned that it is not possible to reach such savings.
"One reason as to why the health savings in this Budget appear larger than all other departments, so you're talking €666 in health versus €290m in social welfare, is that the savings in the last couple of Budgets in health simply haven't been achieved," he said.
"It's not a case of saying if the Minister doesn't make his savings: 'Oh, forget about it, and we'll start afresh this year'.
"The savings now are cumulative and now we're getting to these massive figures that have to be made up within one year.
"It's hard to see how they're going to do it."