The two main forms of diabetes are called type 1 and type 2 diabetes. Although they have different causes and, to a great extent, affect different categories of people, they share three main features.

First, type 1 and type 2 diabetes are both characterized by metabolic abnormalities that include high levels of blood sugar in the circulation, as well as increased levels of other nutrient breakdown products that are released from their storage sites.

Second, decreased insulin secretion or a decreased sensitivity to insulin action is the reason for these metabolic abnormalities. In the case of type 1 diabetes, the body makes no or very little insulin because the insulin secreting islets have been harmed or destroyed. In type 2 diabetes, the body cannot meet the increased insulin demands brought on by a condition called insulin resistance.

Thirds, both types of diabetes can result in long term complications that affect the small vessels of the eyes, kidneys, and nervous system.

These complications are related to the high levels of blood sugar that are sustained over time and can result in serious damage such as blindness, kidney failure, foot ulcers and amputation, and the dysfunction of other organs.

Both type of diabetes also substantially increase the risk of developing heart disease and stroke. In the short term, very high blood sugars, if not treated, can lead to sever dehydration and can cause confusion, coma and even death.

However, the two types of diabetes also have big differences. Type 1 diabetes characteristically occurs in children and young adults (once called juvenile onset diabetes) and requires treatment with insulin for survival (also called insulin dependent diabetes). In type 1 diabetes, the bodies immune system attacks the pancreas. This autoimmune attack destroys the beta cells, leaving them unable to make insulin.

The causes of type 1 diabetes are not fully understood. We don't know what triggers the immune system to start attacking the pancreas, although certain inherited genes can make you more vulnerable.