Clinical Outcomes and Complications of Basal, Bolus, and Combination Insulin Regimens in Type 2 Diabetes Mellitus: Evidence from Published Case Reports.

Insulin therapy remains a cornerstone in the management of type 2 diabetes mellitus (T2DM), especially in patients experiencing progressive loss of pancreatic beta-cell function or those with inadequate glycemic control despite oral antidiabetic therapy. This review synthesized clinical outcomes from 44 peer-reviewed case reports published between 2019 and 2024, identified through systematic searches in PubMed and Scopus. The included cases involved 15 males and 29 females, with patient ages ranging from 11 to 91 years (mean 53 ± 20.85 years). Subcutaneous insulin was the most frequently used route of administration, while intravenous insulin was reserved for managing acute complications. The most commonly reported complication was diabetic ketoacidosis (DKA), especially in patients with delayed insulin initiation or in those receiving sodium-glucose cotransporter 2 (SGLT2) inhibitors, a class of oral glucose-lowering agents, one of whose side effects is known to elevate the risk of euglycemic DKA. Other triggers included COVID-19 infection and severe insulin resistance. Most patients received basal insulin regimens, whereas basal-bolus combinations were preferred in more complex or unstable cases. Insulin was frequently combined with oral agents, such as metformin, dipeptidyl peptidase IV (DPP-IV) inhibitors, glucagon-like peptide 1 (GLP-1) receptor agonists, or sodium-glucose cotransporter 2 (SGLT2) inhibitors, reflecting a trend toward individualized treatment strategies. Biomarkers such as glycated hemoglobin (HbA1c) and C-reactive protein (CRP) were routinely used to monitor glycemic control and systemic inflammation. These findings underscore the clinical importance of early insulin initiation, continuous monitoring, and personalized regimens to improve outcomes in advanced or complicated T2DM. Emerging therapies, such as once-weekly basal insulin formulations, show promise for enhancing adherence and glucose stability, although further research is needed to evaluate their long-term effectiveness and cost-efficiency.