The Irish Blood Transfusion Service (IBTS) has issued an urgent appeal for people to donate blood.
The IBTS said supplies have fallen to a level that is only sufficient for three days.
That is just under half the required level for an average week.
Dr Paul McKinney of the IBTS said current blood stocks are at a critically low level.
Dr McKinney said: “We are well short of where we need to be to ensure that we can continue to supply hospitals where blood demand has been very high for a sustained period.
“It is critical that we get our stocks back up.”