"Diabetes" is not a single disease, but a group of disorders. The more common types of diabetes are:
Type I diabetes: People with type I diabetes cannot make enough insulin. It is thought that type I diabetes develops when a person with a genetic predisposition to the condition is exposed to some environmental factor (such as a virus) that triggers the destruction of the cells in the pancreas that produce insulin. Type I diabetes often occurs in younger, otherwise healthy individuals, which is why it is often called juvenile diabetes. Since these individuals cannot make insulin themselves, the vast majority of type I diabetics must be treated with insulin injections, which is why this condition is also called insulin-dependent diabetes.
Type II diabetes: People with type II diabetes often make plenty of insulin, but they do not respond normally to insulin -- a condition called insulin resistance. People who develop type II diabetes have a genetic predisposition to insulin resistance, and then become overweight and sedentary. Before these individuals develop outright diabetes (that is, before their blood glucose levels become abnormally high), they most often pass through a phase of "pre-diabetes" (also known as metabolic syndrome). Because type II diabetes is associated with long-term weight accumulation and lack of exercise, it is most often seen in older people. However, in recent years, as our population becomes more obese, type II diabetes is now being seen commonly in teenagers. Because type II diabetes can often be treated without using insulin injections, it is sometimes referred to as non-insulin-dependent diabetes.
What Problems Are Caused By Diabetes?Hyperglycemia (high blood glucose levels) itself can cause a lot of problems, including excessive hunger and thirst, frequent urination, weight loss, dehydration, and diabetic ketoacidosis (a potentially life-threatening accumulation of acids in the blood).
In addition, diabetes often produces longer-term medical problems. These include accelerated atherosclerosis, which can lead to coronary artery disease, stroke, and peripheral artery disease; diabetic kidney disease; diabetic neuropathy; and diabetic retinopathy.
National Diabetes Information Clearinghouse. Introduction to Diabetes. http://diabetes.niddk.nih.gov/intro/index.htm. (Accessed January 27, 2011)
American Diabetes Association. Diagnosis and classification of diabetes mellitus. Diabetes Care 2008; 31 Suppl 1:S55.