The intervention will be applied to one clinical area or ward in each participating hospital. Both clinical areas will be audited during a two-week baseline observation period. The two areas will then be randomly allocated to either the intervention of labeled blood bags or no intervention. Auditing will carry on in both areas until 2 weeks after the intervention has been introduced. To assess the longer-term impact of the intervention, there will be a further two-week period of audit 8 weeks from the start of the intervention. The intervention will be carried out for the full 10-week period.