Type 2 diabetes mellitus (T2DM) is epidemic in most developed and many developing countries. Owing to the associated morbidity, mortality and high costs of care, T2DM is an important global public health challenge and target for prevention. Patients at high risk for T2DM (referred to as having
prediabetes) can be easily identified based on fasting
glucose levels or responses to an oral
glucose tolerance test (OGTT). More recently,
glycosylated hemoglobin (i.e. HbA1c, which is also termed A1C in the US) has also been introduced as a diagnostic tool for both
prediabetes and diabetes. Such patients are also at risk for
cardiovascular disease (CVD). Since
obesity and physical inactivity are important risk factors for T2DM, lifestyle interventions, emphasizing modest
weight loss and increases in physical activity, should be recommended for most patients with
prediabetes. Such interventions are safe and effective and also reduce risk factors for CVD. A number of oral
antidiabetic agents have been shown to be effective at delaying onset of T2DM in patients with
prediabetes.
Thiazolidinediones (TZDs) are the most effective, reducing incident diabetes by up to 80%.
Metformin,
acarbose and
orlistat also reduce incident diabetes, but their efficacy is much lower than the TZDs. Pharmacologic interventions may be appropriate for patients at particular risk for developing diabetes, but the benefits of treatment need to be balanced against the safety and tolerability of the intervention. If pharmacologic treatment is warranted,
metformin should be considered first because of its favorable overall safety, tolerability, efficacy and cost profile.