Background: Hypokalemia is considered when the serum potassium level is less than 3.5 mmol/L. Clinical research indicates that hypokalemia affects 20% of hospitalized patients, and in 24% of these cases, inadequate interventions result in life-threatening complications. At present, there is no research available on the prevalence, management, and outcomes of hypokalemia in hospitalized patients, which justifies the need for this study. Aim: The study aimed to examine the prevalence of hypokalemia and the effectiveness of its management in hospitalized patients within the internal medicine department, in relation to the knowledge of doctors and resident physicians. Materials and Methods: This hospital-based retrospective study included a total of 553 cases of patients hospitalized in the Internal Medicine Department of the Mongolia Japan Hospital between January 2024 and August 2024. Patients with a potassium level of <3.5 mmol/L were diagnosed with hypokalemia, and the effectiveness of potassium replacement therapy was evaluated according to the method of supplementation employed. Results: The prevalence of hypokalemia among hospitalized patients in the Internal Medicine Department was 9.8% (54 cases). Based on the study criteria, 42 cases of hypokalemia were selected for further analysis, and a total of 118 potassium replacements were performed through oral, intravenous, and mixed methods. Following potassium replacement therapy, 37.3% (44) of patients achieved normalized potassium levels, while 62.7% (74) still had persistent hypokalemia. Conclusion According to the study results, the prevalence of hypokalemia among hospitalized patients in the Internal Medicine Department is 9.8%. The method of potassium replacement and the severity of hypokalemia do not impact the normalization of potassium levels, with the critical factor being the proper dosage of supplementation. The knowledge of doctors and resident physicians regarding hypokalemia is insufficient, and there is a need to implement guidelines and protocols for potassium replacement therapy in daily clinical practice.