Hospitals may have to start cancelling surgeries if there is no increase in blood donations in the coming weeks.
The Irish Blood Transfusion Service (IBTS) says there is an urgent need for donors to give blood.
There is currently three days worth of stock across the main groups - around half of the usual levels.
Operations director with the IBTS, Barry Doyle, says it's crucial people come forward.
"Three days is a position where we have issued a notification to hospitals to request conservation of blood ordering. If we were to get to two days of stock we may need to cancel surgeries nationally that require blood support."
"Obviously, we are doing everything we can to avoid that," he added.
In an interview with BreakingNews.ie last month, IBTS chief executive Orla O'Brien said the coming winter will present significant issues, with new donors required to keep up with demand.
The need for young donors has been exacerbated by a new policy of not taking blood from healthcare workers and people over 70, with both groups more vulnerable due to the pandemic, she explained.
Twenty thousand donors are in the over-70s age bracket, so they need to be replaced.
“We have to fill that at the far end, 18, 19 up and that’s where the first time donor hit affected us. Normally we’d have 20,000 new donors each year, last year it was 7,500, if we don’t replace that 20,000 back in we have to hit our 80,000 donors [overall] more if there’s less of them.
“The demand will be very high with a slightly smaller pool, so we need new donors and our existing donors to continue giving blood.
“They’ve been amazing and huge credit to them because we have had donors through thick and thin still donating in the pandemic, that is an amazing thing as a country we’re extremely altruistic, so we’re very lucky that way.”
