CausesBy Mayo Clinic staff
The exact cause of type 1 diabetes is unknown. In most people with type 1 diabetes, the body's own immune system — which normally fights harmful bacteria and viruses — mistakenly destroys the insulin-producing (islet) cells in the pancreas. Genetics may play a role in this process, and exposure to certain viruses may trigger the disease.
The role of insulin
Once the islet cells are destroyed, you'll produce little or no insulin. Insulin is a hormone that comes from the pancreas, a gland situated behind and below the stomach.
- The pancreas secretes insulin into the bloodstream.
- The insulin circulates, enabling sugar to enter your cells.
- Insulin lowers the amount of sugar in your bloodstream.
- As your blood sugar level drops, so does the secretion of insulin from your pancreas.
The role of glucose
Glucose — a sugar — is a main source of energy for the cells that make up muscles and other tissues.
- Glucose comes from two major sources: food and your liver.
- Sugar is absorbed into the bloodstream, where it enters cells with the help of insulin.
- Your liver stores glucose as glycogen.
- When your insulin levels are low, such as when you haven't eaten in a while, the liver converts stored glycogen into glucose to keep your glucose level within a normal range.
In type 1 diabetes, there's no insulin to let glucose into the cells, so sugar builds up in your bloodstream, where it can cause life-threatening complications.
The cause of type 1 diabetes is different from the cause of the more familiar type 2 diabetes. In type 2 diabetes, the islet cells are still functioning, but the body becomes resistant to insulin, or the pancreas doesn't produce enough insulin or both.
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