The issue of the most appropriate red blood cell transfusion policy has been addressed by a number of randomised controlled trials, conducted over the last decades, comparing the effects on patients' outcome of restrictive blood transfusion strategies (transfusing when the haemoglobin concentration is less than 7 g/dL to 8 g/dL) vs more liberal ones (transfusing when the haemoglobin concentration is less than 9 g/dL to 10 g/dL) in a variety of clinical settings. In parallel, various systematic reviews and meta-analyses have tried to perform pooled analyses of the data from these randomised controlled trials and their results have been utilised by scientific societies to provide recommendations and guidelines on red blood cell transfusion thresholds. All these aspects will be critically discussed in this narrative review.