The Irish Blood Transfusion Service says it's struggling to maintain blood stocks and is under pressure to fill clinics.
It usually holds a seven day stock of blood, however after the long weekend the reserve fell to just four.
The IBTS was forced to import 390 units of blood from the UK after a shortage at the end of last year.
Regular donors who are contacted by text are being asked to book an appointment as soon as possible.
Barry Doyle of the IBTS says this is the first time this year that blood stocks have dipped to this point:
"We've actually been very good since the end of January, and our donors have been fantastic and bank holidays can have an impact.
"Usage is very high, which is fantastic for the hospitals and for patient services, but usually with a an accu accumulation of bank holidays, things can get a little bit tight.
"So we just need donors to respond now if they can."
