Diabetes type 1 is an autoimmune disease.
When you have diabetes type 1, your immune system’s autoreactive T-cells (a type of white blood cell) attack the beta cells in your pancreas. Once enough of the beta cells are destroyed, your body can no longer produce Insulin.
This is problematic for two reasons:
- No uptake. Insulin’s main job is to let Glucose enter the muscle and fat cells that need it (it moves the glucose transporters to the cell surface). Without insulin, glucose is locked out of those cells.
- No storage. Insulin also signals the liver and muscles to store surplus Glucose as Glycogen. Without insulin, that storage stops too.
So without insulin your blood ends up full of glucose, but your cells are starving, there’s no way to use it and no way to store it, so it just keeps building up in the blood.
Because the cells can’t get glucose for fuel, the body starts burning fat instead. Burning fat produces Ketones. When there are too many ketones in the blood this causes ketoacidosis, which is dangerous.
Note: insulin doesn’t only fail at storage, it normally also tells the liver to stop releasing glucose. Without it, the liver keeps dumping more glucose into the blood, making the high blood sugar even worse.