Blood Transfusion Formulas


1 How to calculate the interval between blood transfusions


Number of days before the next transfusion = (Post transfusional Hb  Target pretransfusional Hb) ÷ post transfusional Hb x 100 The target pre transfusional Hb varies from 90 to 100 g/l


2 How to calculate the blood volume needed to raise the hemoglobin to a specific level


The volume of packed RBC in ml = (The target Hb  The observed Hb) x Patient's weight in Kg x local factor (3 or 4 usually) The Local factor can be calculated from the following equation: 3/Hct of the PRBC Example 3/0.6=5, note that most Packed Red Blood Cell products have a hematocrit of 0.4 to 0.8



