Subtypes of Type 2 Diabetes Mellitus and their implications for clinical practice

The goal of this review article is to describe the four subtypes or clusters of Type 2 DM. We believe that differentiating these subtypes based on clinical and laboratory characteristics—such as glutamic acid decarboxylase antibodies (GAD), age at onset of Type 2 DM, HbA1c, body mass index (BMI), and measures of insulin resistance and insulin secretion—can help characterize them. The main purpose of defining these clusters is to understand how to tailor treatment and prevent complications that vary among these groups. The severe insulin-deficient group at diagnosis resembles Type 1 diabetes mellitus but lacks autoantibodies against beta cells and has different genetic markers. Microvascular complications like diabetic neuropathy and retinopathy are most common in this subtype, as well as cardiovascular complications. Insulin treatment should be started early in this group. The insulin-resistant subtype is linked to the highest rate of diabetic nephropathy. Efforts to decrease insulin resistance and protect kidney function are essential in this cluster. The mild obesity-related subtype and the mild age-related subtype generally have a lower risk of complications and respond well to lifestyle changes and weight loss. Identifying these subtypes of Type 2 DM allows for a personalized approach to disease management.