Indications for transfusions of red blood cells (RBC) are anemias, which can occur after trauma, in surgery, in obstetrics or oncohematology wards. The main criteria to administer RBC transfusion are hemoglobin level and clinical features. Transfusions are rare when the hemoglobin level is above 10 g/dL and are frequent when it is below 6 g/dL. However clinical setting, patient age, associated diseases, cardiovascular complications are taken into account. Immunocompatibility should always be tested and the transfusion consequences checked immediately and on the long term. Platelet transfusions are performed when the platelet count is low and patients suffered from hemorrhage. In oncohematology patients, platelet transfusion are administered with prophylaxis when the platelet count is lower than 10 g/L. Fresh frozen plasma has now a limited use, only in complex haemostatic disorders and in hemolytic uremic syndrome.