The Irish Blood Transfusion Service has warned that supplies of certain blood types are "critically" low and has issued a pre-amber alert to hospitals as it appeals for donors.
IBTS Operations Director Paul McKinney said the problem is "simply a supply and demand situation".
Speaking on RTÉ's Morning Ireland, he said despite clinic collections actually being very strong over what is traditionally a very challenging period for the service, the demand from hospitals, particularly for O-negative, the universal blood group, and other rhesus negative groups, is not being matched by supply.
Mr McKinney said "unfortunately we find ourselves this morning where we have less than two days' stock of O-negative, less than two days for B-negative and just three days stock for A-negative".
He added: "It's a very challenging position. We're asking regular donors, please if they receive a text from us to make an appointment to donate if you would also like to make an appointment if you're O-negative, please ring our number - 1800 731137. Make sure you do our eligibility quiz which is on our website Giveblood.ie.
"Unfortunately [it’s] quite a serious situation we're facing."
In order to avoid surgeries being postponed, the IBTS is appealing for donors.
"We have issued a letter and we're in full communication with the hospitals, obviously observing the national blood shortage plan. We have issued a pre-amber letter to the hospitals and we're hoping to build up our stocks in those groups."
Mr McKinney said the IBTS has never had to issue an amber letter, which would mean that hospitals would "have to start considering whether non-essential operations should take place or could they be delayed or postponed".
Regular donors are being urged to donate to "plug" the current issue as new donors have to be processed and that takes longer to get them through the clinic, Mr McKinney said.
He appealed to anyone interested in donating blood to go to the IBTS website and register their interest.
