The notion of transfusion threshold is criticized because transfusion is a complex decision, taking into account the rate of bleeding and clinical tolerance. With the reservations that this concept imposes, the following thresholds are retained in the event of acute anemia, after correction of hypovolemia: Hbmini = 7 g/dl in people with no particular history, Hbmini = 8 - 9 g/dl in people with a history of cardiovascular disease, Hbmin = 10 g/dl in people not clinically tolerating the lower concentrations or suffering from acute coronary insufficiency or proven heart failure. For children, infants... the thresholds depend on the indications and are given by the local recommendations.
The hemoglobin level of a red blood cell is generally indicated on its label, but is standardized, > 40g most of the time, with an average of 55g. This standard may vary by country.
The volume of red blood cells is also indicated on its label. For an adult, this data is of little use (transfusion of whole RCCs). For children, a value in ml can be given, which is more precise and adapted to the pellet than the 3 to 4 ml/kg for 1g of Hb usually admitted. However, transfusion efficiency can only be measured on biological and clinical controls.