Diabetes interferes with the body's ability to store energy from food. The pancreas makes a substance called insulin that helps the body turn food into stored energy. Type 1 diabetes (juvenile diabetes) occurs when the pancreas stops making insulin. In type 2 diabetes (adult-onset diabetes), the body makes adequate amounts of insulin but cannot use it normally. In both cases, the result is high blood sugar levels. Over time, high blood sugar levels can lead to a number of complications, including blindness, kidney failure, nerve damage, and cardiovascular disease (heart disease and stroke). Fortunately, good care with diet, exercise, and medications to control blood sugar levels clearly prevents or delays the development of diabetes-related blindness, kidney failure, and nerve damage. The relationship between blood sugar control and cardiovascular disease is less clear. Glycosylated hemoglobin concentration is a blood test that measures blood sugar control over the previous 3 months.