Type 2 diabetes mellitus interferes with the body's ability to store energy from food. The result is high blood sugar levels that can lead to complications, such as blindness, kidney failure, and heart disease. Many people with type 2 diabetes have moderately high levels of blood sugar for years before the levels reach true diabetes levels and symptoms begin. This condition is called abnormal glucose tolerance or “prediabetes.” A large study showed that 2 different methods can prevent or delay the development of diabetes in people with prediabetes. The first method is an intensive diet and exercise program supervised by a clinic. The other is a small daily dosage of a diabetes medication called metformin. Because many Americans have prediabetes, using 1 of these prevention methods in all people who might benefit would be expensive. However, caring for diabetes and its complications is also expensive. It is important to know whether the costs of diabetes prevention are worth the potential benefits. A previous analysis using a computer model estimated that, compared with no prevention, the diet and exercise program would cost about $8800 and metformin about $29,000 per quality-adjusted year of life saved.