What causes type 1 diabetes?

The exact cause of type 1 diabetes is not known, but it is thought to be an autoimmune disease. Autoimmune diseases are those in which the body's immune system attacks and destroys its own tissue — in this case, the cells in the pancreas that make insulin (called islet cells). This means that the pancreas makes little or no insulin, resulting in higher than normal blood glucose levels (more than 8 millimoles [mmol] of glucose per litre [L] of blood).

Type 1 diabetes usually runs in families, so if you have a close relative (a parent, brother or sister) with type 1 diabetes, you are more likely to develop it compared with someone who is not related to anyone with type 1 diabetes. This means that there may be a genetic cause for why the body’s immune system attacks the pancreas in type 1 diabetes.

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