HSE chief Tony O'Brien will face questions from TDs and Senators today over exactly how many people will lose their medical cards next year.
The Government has ordered that €113m be cut from the medical card scheme as part of Budget 2014 - but has not explained just how many people will be affected.
The Public Accounts Committee will hear exactly how the health service plans to make those cutbacks - and whether the adjustment is even a realistic target.
Sinn Féin TD Mary Lou McDonald said that people have medical cards for a reason, and their lives could be jeopardised by the cuts.
"Anybody who is holding a medical card, they hold it because they are on a low income, perhaps they're out of work, or indeed because they are chronically or seriously sick," she said.
"I don't believe any Minister for Health that's serious about protecting people's health goes about stripping those very people of their medical cards and in turn access to the very services that they need to keep themselves well, or in some cases, to keep themselves alive."