The pancreas of an individual with type 1 diabetes does not produce the hormone insulin, which is essential to allow body tissues to take up and use glucose from the blood. Before the discovery of insulin in the 1920s, such people had little chance of living a normal lifespan. And even with insulin injections, it is difficult to keep blood sugar within normal boundaries. Too little insulin, or insulin injected at the wrong time, could mean high blood sugar and later complications such as blindness and kidney failure. Conversely, too much insulin could mean hypoglycemia (low blood sugar), which in turn can lead to passing out a real threat if a person is driving, for example.