Method of monitoring medical item inventory

A medical item inventory system includes a plurality of different types of stored medical items. The system can track a quantity of a medicinal substance type removed from its storage location, including the quantity used and the quantity returned to storage. The system can monitor the medical item inventory in real time to automatically determine a low supply of a particular medical item type. In response to a determination of a low supply of a particular medical item type, the system automatically electronically places a purchase order to a supplier of the particular medical item type. The purchase order includes the particular medical item type, a requested quantity, and a requested delivery date. The requested quantity and delivery date can both be calculated by the system based on a rate of use of the particular medical item type.