The service, which usually holds a seven-day supply across all blood groups, said recent bad weather has resulted in fewer people donating blood.
In addition, demand from hospitals has been far higher than anticipated, contributing to the shortfall.
A number of extra clinics were in operation across the country yesterday, which attracted more than 300 donations, while more are planned for this, and coming, weeks.
“In an effort to improve the supply levels and maintain services to patients, the IBTS is asking donors to make a special effort to attend clinics in the next two weeks and if you can, bring a new donor with you,” said Paddy Bowler, operations director at the IBTS.
Between December 21 and January 3, blood donations were down by 13.3%. During the same period, demand for blood in hospitals was 6.5% higher than expected.
While this trend eased somewhat in the first few weeks of this month, hospital demand continues to be 3% higher than expected while donations continue to be 2.5% lower.
Mr Bowler said flooding and poor conditions towards the end of the year severely affected the amount of people donating to blood clinics.
“The bad weather in the Christmas/New Year period definitely impacted donor attendance levels,” he said.
“In many of our collection areas, due to flooding, local advice from the gardaí was not to travel unless absolutely necessary. The second day of the Bandon clinic was cancelled due to bad weather.
“Due to the high levels of exclusions for haemoglobin we need more donors to come forward. We are especially asking those donors who have not donated for some time to come back and to those who have thought about donating, this is your opportunity to assist patients needing blood.”
As such, the IBTS is running a number of blood donation clinics across the country.
Clinics in Cork City are in operation today, tomorrow, and Thursday, in Clonakilty today and tomorrow, and in Kinsale on Thursday. Clinics in Limerick, Clare, Dublin, and other areas will also be open today, tomorrow, and Thursday.
For more details log onto www.giveblood.ie.