In hospitalized patients, hyperglycemia is frequently observed in patients with and without diabetes. Inpatient hyperglycemia worsens outcomes, potentially leading to infection, post-operative complications, and even death. Therefore, it is important to control blood glucose level in an inpatient setting. However, in these patients, it can be difficult to achieve adequate glycemic control due to the disease itself (e.g., infection), treatment drugs (e.g., corticosteroids), procedures requiring fasting, or enteral/parenteral nutrition therapy. In most cases, insulin therapy is required. We reviewed the insulin treatment regimens in hospitalized patients.