Objective: The prevalence of drug-related problems in elderly patients is a concerning issue that can lead to elevated morbidity, mortality, and health care resource utilisation. This study focuses on the significance of addressing diabetes in the context of an ageing population, where elderly individuals face higher risks of comorbidities and mortality. The main objective of this study was to assess potentially inappropriate medications (PIMs) and potential prescribing omissions (PPOs) among patients with diabetes in Bulgaria, using the explicit STOPP/START criteria, version 2. By evaluating the appropriateness of drug prescriptions in this specific patient population, this study aims to shed light on areas that require optimisation to enhance patient safety and treatment outcomes. Materials and methods: A national prospective questionnaire study was conducted in Bulgaria among patients aged over 65 years. The research was conducted in 25 randomly selected pharmacies. The study supports the use of the STOPP/START criteria based on the clinical information provided. A total of 133 patients with T1DM or T2DM participated in the study. The evaluation of potentially inappropriate medications (PIMs) and potential prescribing omissions (PPOs) was performed in 131 patients. sStatistical differences in demographics and medication numbers between patients with and without PIMs or PPOs were assessed using a Chi-square test, with a p-value of ≤ 0.05 considered statistically significant. Results: The pharmacotherapy of 131 patients with diabetes was assessed, and it was found that 57% of them had polypharmacy. Among the study population, 90 PIMs were identified, indicating that 66% of the patients had inappropriate prescribing. Notably, inappropriate prescribing concerning diabetes was associated with the use of long-acting sulfonylureas (n=10) and beta-blockers (n=13). Applying the START criteria revealed 67 PPOs among 67 patients, representing a prevalence of 50% in the study population. However, no PPOs were detected in the context of diabetes pharmacotherapy. Furthermore, a significant relationship was observed between the number of medications and PIMs, as evidenced by the chi-square test result with a p-value close to zero, indicating statistical significance. Conclusion: The study revealed a high prevalence of PIMs in elderly patients with diabetes in Bulgaria. Endocrine disorders contribute to 26% of PIMs. As Bulgaria’s ageing population faces increasing diabetes challenges, effective management strategies are crucial. These findings underscore the significance of addressing prescribing practises to enhance disease control and prevent complications.