BACKGROUND: Proper pharmaceutical inventory management is critical in guiding decisions that mitigate cyclic stockouts. It sets purchasing priorities, informs the procurement of cost-effective drugs, and ensures that there is a balance between inventory expenditure and the demand for medications. This study aimed to evaluate the drug consumption and expenditure patterns at a leading referral hospital in Western Kenya i.e. the Jaramogi Oginga Odinga Teaching and Referral Hospital (JOOTRH). Drug consumption and expenditure data at JOOTRH was analyzed over 3 years (2018-2020) using Therapeutic Class (TC), Always Better Control (ABC), and Vital Essential and Non-essential (VEN) analysis. Data sources included the Kenya Health Information System (KHIS), bin cards, invoices, delivery notes, and patient files. RESULTS: The total pharmaceutical expenditure (TPE) over the study period was $ 1,329,213.91. The annual pharmaceutical expenditure (APE) was $ 389,158.51, $ 501,365.79, and $ 438,689.61 for 2018, 2019, and 2020 respectively. ABC analysis indicated that 53 (18.9%), 56 (19.9%), and 56 (19.9%) of items were Class A medicines in 2018, 2019, and 2020, respectively and consumed 70.2%, 71.7%, and 72.7% of the APE in 2018, 2019, and 2020 respectively. VEN analysis revealed that 173 drugs were classified as vital items in each of the years 2018, 2019, and 2020 and consumed 77.7%, 75.1%, and 74.2% of the APE in 2018, 2019, and 2020 respectively. TC analysis indicated that anti-infectives were the most consumed class of medicine over the study period and consumed 27.4%, 23.5%, and 30.4% of the APE in 2018, 2019, and 2020 respectively. CONCLUSIONS: According to this analysis, Category I pharmaceuticals accounted for the majority of the total pharmaceutical expenditure at the hospital and require special attention for control.