Red cell (blood) transfusions are given to treat symptomatic anaemia.  For haematology patients, these are given in the Haematology Day Stay unit.  Two to three units of red cells are usually given.  Each unit takes approximately two hours.  Before your transfusion, you will be asked to have a special blood test for crossmatching purposes, so that the correct blood can be issued.  If you have had a transfusion within the past three months, this must take place no greater than 72 hours prior to the transfusion.  If you have never received blood or if it was greater than three months ago, then the sample may be taken up to seven days prior to the transfusion.