Think of each of the billions of cells in your body as a tiny machine. Like all machines, cells need fuel. The foods you eat are made up of carbohydrates, proteins, and fats, which are broken down to provide fuel for the cells. The main fuel use by the cells is called glucose, a simple sugar. Glucose enters your cells through receptors.
Receptors are sites on cells that accept insulin and allow glucose to enter.
Once inside, glucose can be used as fuel. But glucose has difficulty entering your cells without insulin. Excess glucose is stored in the liver and muscles in a form called glycogen. Between meals, when your blood sugar is low and your cells need fuel, the liver glycogen is released to form glucose. The pancreas is located in the abdomen, behind the stomach.