In healthy people, insulin is produced by the pancreas: When you eat or drink, food is broken down into smaller parts, some of which is a form of sugar. Insulin acts like a key: unlocking cells so that sugar can move from the blood into the body tissues, to be used for energy. Diabetes is a problem with the function of insulin: either the key (insulin itself) isn’t working, or the lock (the cell) struggles to let sugar into the cell. When you have “high blood sugar” – the body produces too little insulin, or the tissues don’t respond to insulin in the way they’re supposed to. The end result is excess sugar in the blood, while body cells are starved of their fuel and go hungry. Common symptoms of diabetes are excessive thirst, excessive passing of urine, and often a large appetite. Dramatic weight loss can also be an early warning sign, due to the starvation of body tissues.