Objectives: Blood inventory level is required to predict blood shortage at a national level. The purpose of this report is to monitor the blood inventory level based on the data provided by the Korea blood inventory monitoring system (KBIMs), the ongoing national surveillance system for blood management. Methods: The current report includes data from 25 sentinel hospitals that participate in the KBIMs. The blood inventory ratio for 25 sentinel hospitals is proposed and the individual control chart is used to detect the changes in the mean of the inventory ratio. Results: Blood type A has an inventory ratio between 5.2 and 4.4 days, the lowest among all blood types, during 2009-2012. In addition, the annual mean value of the inventory ratios of both blood type A and O decreased consistently every year. Control chart shows that all blood types are out-of-control status since the mid of 2010. Conclusions: Simply by setting and modifying the control chart, we can develop a reasonable control chart which reflects the current status.