Diabetes interferes with the body's ability to store energy from food. The pancreas makes a substance called insulin, which helps the body store energy from food. Type 1 diabetes (juvenile diabetes) occurs when the pancreas stops making insulin. In type 2 diabetes (adult-onset diabetes), the body makes plenty 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 blindness, kidney failure, nerve damage, and heart disease. Good care with diet, exercise, and medications can prevent complications. Type 1 diabetes usually does not go long before being diagnosed. However, many people with type 2 diabetes have it for years before symptoms begin.