Causes of diabetes Dr Rob Hicks Find out what's at the root of type 1 and type 2 diabetes.

In this article

Type 1

Type 2

What doesn't cause diabetes?

In type 1 diabetes the cells in the pancreas that make insulin are destroyed, causing a severe lack of insulin. This is thought to be the result of the body attacking and destroying its own cells in the pancreas - known as an autoimmune reaction.

It's not clear why this happens, but a number of explanations and possible triggers have been proposed. These include:

• infection with a specific virus or bacteria
• exposure to food-borne chemical toxins
• exposure as a very young infant to cow's milk, where an as yet unidentified component triggers the autoimmune reaction

However, these are only hypotheses and are not proven causes.

In this type of diabetes the receptors on cells in the body that normally respond to the action of insulin fail to be stimulated by it - this is known as insulin resistance.

In response to this, more insulin may be produced, and this overproduction exhausts the insulin-manufacturing cells in the pancreas. There is simply insufficient insulin available and the insulin that is available may be abnormal and so doesn't work properly.

The following risk factors increase the chances of someone developing type 2 diabetes:

• increasing age
• obesity
• physical inactivity

Rarer causes of diabetes include:

• certain medicines
• pregnancy (gestational diabetes)
• any illness or disease that damages the pancreas and affects its ability to produce insulin, such as pancreatitis

It's important to be aware of myths about the causes of diabetes. Eating too much sugar does not cause diabetes. However, it may cause obesity and this is associated with people developing type 2 diabetes.

Stress does not cause diabetes, although it may be a trigger for the body turning against itself, as in type 1 diabetes. But it does make the symptoms worse for people who already have diabetes.

Diabetes is not contagious. Someone with diabetes can't pass it on to anyone else.

This article was last medically reviewed by Dr Rob Hicks in March 2007.
First published in April 2001.