Background: Patients’ awareness and understanding about purchasing medicines is crucial to protect them from untoward incidents arising from a faulty purchasing process. This study was conducted to assess the practices related to buying and use of medicines among adult patients admitted to a tertiary healthcare facility. Materials and methods: This cross-sectional study was conducted in May 2024 using a purposive sampling method among 205 adult patients admitted to the medical and surgical wards of a tertiary health care hospital in Thane. Data related to the sociodemography of the patients and their practices related to purchasing and use of medicines were collected in a suitable proforma. The data were entered into Microsoft Excel and analyzed. The Chi-squared test was applied. The statistical level of significance was fixed at p < 0.05. Results: About 205 adult patients were interviewed, of which 127 (61.95%) were males and 78 (38.05%) were females. One hundred sixty-eight (81.95%) were literate, while 37 (18.05%) were illiterate. One hundred seventy-one (83.41%) patients check the expiry date, and 131 (63.90%) go through the MRP of the medicines while buying them. Eighty-one (39.51%) patients had encountered poor quality medicines in the past. Forty (19.51%) patients were aware of the consumer court for redressal of grievances. Six (2.93%) patients had filed a case in the consumer court against a medical shop for poor quality of purchased medicines. One hundred twenty-seven (61.95%) subjects had purchased medicines without a prescription, and 32 (15.61%) had used expired medicines in the past during an emergency. Conclusion: There is a need to create awareness among patients about buying and properly using medicines prescribed by a doctor to avoid untoward incidents.