The global pharmaceutical drug shortage and the uncertain clinical demand make it difficult for medical managers to make the right decisions. This study simultaneously considers the uncertainties of drug supply and demand, and develops a reorder model for hospital medication to maintain proper inventory costs and reduce the occurrence of drug shortages. Based on five indicators, this study classifies medicines using ABC classification, and develops a reorder model for each category of medicines. The analysis of actual data found that all five indicators can significantly reduce the number of out-of-stock days by 85% to 90%; the total inventory cost slightly varies between -0.7% to 5.7%. Therefore, the proposed reorder policy can effectively deal with the unpredictable shortage risk and improve the medication inventory management.