Addition of insulin to oral therapy in patients with type 2 diabetes.

Background: A majority of individuals with type 2 diabetes will eventually require exogenous insulin therapy to achieve or maintain glycemic control. This review provides practical recommendations for adding insulin therapy for patients with type 2 diabetes whose glucose levels are inadequately controlled with oral medications.

Methods: We used a systematic review of MEDLINE to retrieve relevant articles from 1990 to 2004 using the search terms insulin therapy, combination oral therapy, glycemic control, insulin analogs, insulin glargine, and basal insulin, which we supplemented with a review of clinical practice guidelines from the American Diabetes Association and the American Association of Clinical Endocrinologists.

Results: Type 2 diabetes mellitus is becoming more common in the United States and is likely to increase in prevalence as obesity, a risk factor for type 2 diabetes, likewise increases. Treatment often begins with oral monotherapy, but after 3 years of treatment, more than half of patients will require more than one pharmacological agent, and eventually most patients will require insulin. Adding insulin to oral therapy at an earlier stage in treatment provides improved glycemic control without promoting increased hypoglycemia or weight gain, lowers the risk of microvascular complications by 25%, and reduces the amount of insulin patients require. Various insulin preparations, including the newer analog insulins, with different onsets and durations of action are available to help meet individual patients' dosing needs.

Conclusions: The addition of insulin to oral antidiabetic therapy can improve glycemic control. Newer insulin analogs can emulate normal physiologic insulin secretion and potentially limit diabetes-related comorbidity.