Type 1 diabetes is an autoimmune disorder. It's believed that a combination of genetic predisposition and additional (as yet unidentified) factors provoke the immune system into attacking and killing the insulin-producing cells in the pancreas.
Type 2 diabetes is mainly caused by insulin resistance. This means no matter how much or how little insulin is made, the body can't use it as well as it should. As a result, glucose can't be moved from the blood into cells. Over time, the excess sugar in the blood gradually poisons the pancreas, causing it to make less insulin and making it even more difficult to keep blood glucose under control. Obesity is a leading cause of insulin resistance; 90% of people with type 2 diabetes are overweight. There are probably genetic factors involved in the cause of type 2 diabetes as well. A family history of the disease has been shown to increase the chances of getting it.
People with type 1 diabetes who are not being treated urinate frequently and feel excessively thirsty. They usually feel very tired and experience severe weight loss despite normal or excessive food intake.
The symptoms of type 2 diabetes usually appear more gradually. People with type 2 diabetes who do not have their blood glucose under control often have a persistent, mild thirst. They urinate frequently, and often feel mild fatigue and complain of blurred vision. Many women with the disease have recurring vaginal yeast infections.
