The Irish Blood Transfusion Service is opening extra clinics in order to increase donations to meet demand over Christmas.
There is currently a five to six-day supply of blood available to meet the needs of hospitals around the country, and 14,000 donations are needed between now and the New Year.
Up to 1,500 donations will be lost this month because of a new EU directive on iron levels in donors.
Director of Operations with the IBTS, Paddy Bowler, said that, coupled with the way Christmas falls this year, is a cause for concern.