Insulin, a hormone released from the pancreas, controls the amount of sugar in the blood. When people eat or drink, food is broken down into materials, including the simple sugar glucose, that the body needs to function. Sugar is absorbed into the bloodstream and stimulates the pancreas to produce insulin. Insulin allows sugar to move from the blood into the cells. Once inside the cells, it is converted to energy, which is either used immediately or stored as fat or glycogen until it is needed. The levels of sugar in the blood vary normally throughout the day. They rise after a meal and return to normal within about 2 hours after eating. Once the levels of sugar in the blood return to normal, insulin production decreases. The variation in blood sugar levels is usually within a narrow range, about 70 to 110 milligrams per decilitre (mg/dL) of blood. If people eat a large amount of carbohydrates, the levels may increase more. People over 65 tend to have slightly higher levels, especially after eating. If the body does not produce enough insulin to move the sugar into the cells, the resulting high levels of sugar in the blood and the inadequate amount of sugar in the cells together produce the symptoms and complications of diabetes.