Patients with type 2 diabetes have impaired ability to store energy from food and high blood sugar levels. Over time, they may experience complications like kidney disease, heart disease, blindness, and nerve damage (neuropathy). To help avoid some of these problems, doctors try to control patients' blood sugar levels with diet and diabetes drugs. Diabetes drugs include glucose-lowering pills, such as metformin and sulfonylurea drugs. Although these pills help, many patients do not achieve or cannot sustain good glucose control with pills alone. Options for these patients are to add drugs that are given as injections, such as insulin glargine (a long-acting insulin) or exenatide (a new incretin mimetic drug). Because exenatide is a new drug, however, we know relatively little about its benefits and harms compared with insulin.