Blood supplies are not coping with the number of ill people, the National Blood Transfusion Centre said on Thursday.
The centre said there was an "urgent" need for blood of all types amid insufficient donors to keep up with the demand.
"Whoever can help, should show up to donate as soon as possible," it said.
The blood transfusion centre, located next to St Luke's Hospital, is open daily between 8am and 6pm. Donors should provide their ID card or driving licence to donate blood.