Type 2 diabetes mellitus interferes with the body's ability to store energy from food, resulting in high levels of blood sugar that can lead to such problems as kidney failure, blindness, and heart disease. Insulin helps the body convert food to stored energy and keeps blood sugar levels within the normal range. In type 2 diabetes, body tissues are resistant to the effects of insulin and blood sugar levels are high. Some patients can overcome these abnormalities with diet and exercise alone. However, many patients need to add drug treatment to control blood sugar levels. Drugs include insulin, an injectable drug, and a variety of oral drugs. Usually, oral drugs are the first line of treatment. The ACP developed these guidelines to help doctors and patients choose from among the wide variety of oral drug options available to treat type 2 diabetes.