How does blood sugar work? How is sugar transferred into the blood? Sugar in the blood or also called glucose comes directly from what we eat. The digestive system breaks down that food into glucose and absorbs it into the blood. That's why eating foods high in carbohydrates provide most of the glucose in your diet. Once glucose enters the blood, cells throughout the body use it for energy. The pancreas produces insulin as soon as blood sugar levels begin to rise. Insulin is an important hormone that helps transport glucose into cells.