Pancreas's Job

Blood glucose level, called glycemia, is controlled by a well defined process, involving several organs like the liver or the pancreas, and some hormones like insulin. After a meal or whatever you could do (physical exercices, stress...), glycemia tends to increase (or decrease sometimes, with some stress factors). Glucose, which is one of the most important sources of energy for the cells of the organism, needs then to be absorbed. This is one of the jobs of the pancreas. The pancreas contains cells called Beta cells which produce insulin. Insulin is a hormone that will, to put it simply, catch glucose particules and allow them to be absorbed by muscles, organs and cells. The insulin production rate depends on glucose concentration. The more sugar you eat, the more insulin you produce to absorb it, feeding the organism. On the other hand, the pancreas makes glucagon, which produces the opposite effect. When you lack sugar, you produce more glucagon. Those 2 hormones have an important role in the regulation of glycemia.

When you have type 1 diabetes, Beta cells in the pancreas do not work anymore. They are totally destroyed under an auto immune effect of the organism. The pancreas then doesn't distribute insulin anymore. Glucose is not absorbed by the organism, and finally you start to show symptoms of diabete presented before.