This study examined the reduction in medical expenses achieved by pharmaceutical inquiries at a community pharmacy. The total number of inquiries was 1,053 out of a total of 29,875 prescriptions filled at one community pharmacy (incidence: 3.5%). Pharmaceutical inquiries regarding the elimination of prescribed medicines were classified into two categories: leftover (incidence: 0.76%) and those regarding duplicate prescriptions filled by other institutions or drug interactions (incidence: 0.18%). The doctors accordingly reduced the number of medicines after these inquiries, which led to a reduction in dispensing and medical fees. The reduction in patient medical expenses per prescription from leftover medicines was 1,425 yen (median) for children (under 14 years), 390 yen for adults (15-64 years), and 1,165 yen for elderly patients (over 65 years). The reduction in patient medical expenses per prescription from eliminating duplicate prescriptions was 955 yen for children, 250 yen for adults, and 360 yen for the elderly. The reduction in patient medical expenses from leftover medicines was statistically higher compared with that from duplicate prescriptions for elderly patients (P < 0.01). This difference was because of long-term drug prescriptions for cardiovascular diseases and diseases of the digestive and central nervous systems. Our findings show that community pharmacists can effectively reduce patient medical expenses and increase patient safety by responding to pharmaceutical inquiries and collecting leftover medications.