Globally, 1 in 11 adults, or 463 million people, are estimated to be living with diabetes. That number is only expected to rise. In fact, as many as half of all people who have diabetes don't know it. Diabetes is a disease that occurs when your blood glucose, also called blood sugar, is too high. Over time, having too much glucose in your blood can lead to heart disease, nerve damage, eye problems and kidney disease. You can take steps to prevent diabetes or manage it. The following information can help you understand diabetes and how to prevent or control it.