Diabetes mellitus, simply diabetes, is a syndrome characterized by disordered metabolism and inappropriately high blood sugar (hyperglycaemia) resulting from either low levels of the hormone insulin or from abnormal resistance to insulin's effects coupled with inadequate levels of insulin secretion to compensate....

Diabetes mellitus, simply diabetes, is a syndrome characterized by disordered metabolism and inappropriately high blood sugar (hyperglycaemia) resulting from either low levels of the hormone insulin or from abnormal resistance to insulin's effects coupled with inadequate levels of insulin secretion to compensate.

The World Health Organization recognizes three main forms of diabetes mellitus: type 1, type 2, and gestational diabetes (occurring during pregnancy), which have similar signs, symptoms, and consequences, but different causes and population distributions. While, ultimately, all forms are due to the beta cells of the pancreas(a body gland) being unable to produce sufficient insulin to prevent hyperglycemia (high blood sugar).

The causes are different. Type 1 diabetes is usually due to autoimmune destruction of the pancreatic beta cells. Type 2 diabetes is characterized by insulin resistance in target tissues, this causes a need for abnormally high amounts of insulin and diabetes develops when the beta cells cannot meet this demand. Gestational diabetes is similar to type 2 diabetes in that it involves insulin resistance; the hormones of pregnancy can cause insulin resistance in women genetically predisposed to developing this condition.

Diabetes can cause many complications. Acute complications (hypoglycemia (low blood sugar), ketoacidosis (a type of abnormal body metabolism) or nonketotic hyperosmolar coma) (a type of abnormal body metabolism) may occur if the disease is not adequately controlled. Serious long-term complications include cardiovascular(heart) disease (doubled risk), chronic renal(kidney) failure, retinal(eye) damage (which can lead to blindness), nerve damage (of several kinds), and microvascular(small blood vessels) damage, which may cause impotence and poor healing. Poor healing of wounds, particularly of the feet, can lead to gangrene(blackish discoloration due to lack of blood supply), which may require amputation. Adequate treatment of diabetes, as well as increased emphasis on blood pressure control and lifestyle factors (such as not smoking and keeping a healthy body weight), may improve the risk profile of most aforementioned complications. In the developed world, diabetes is the most significant cause of adult blindness in the non-elderly, the leading cause of non-traumatic amputation in adults, and diabetic nephropathy(nerve damage) is the main illness requiring renal(kidney) dialysis.