Diabetes (diabetes mellitus) is a chronic, degenerative disease caused by insulin deficiencies due to the body being incapable of producing normal insulin levels, or insulin resistance, a condition in which the cells of the body resist insulin's attempts at regulating blood sugar levels. Insulin is a hormone produced by the pancreas to metabolize glucose, a form of sugar that is one of the primary sources of cells` energy supply. Whether diabetes is caused by insulin resistance or a lack of insulin, the end result in the same: the body is unable to transport enough glucose from the bloodstream into the cells, especially after meals, when blood sugar levels rise as a natural consequence of digestion.


People with Type I diabetes do not produce enough insulin, or do not produce any insulin at all in their pancreatic islet cells due to beta cell failure or destruction. In Type I diabetes, blood sugar rises because little or no insulin enters the bloodstream. Because insulin is needed to metabolize the sugars, the body's cells cannot get the nourishment they need from glucose and the excess glucose just builds up in the bloodstream. Some glucose may be converted into fat, but most spills out into the urine.

Type II diabetes is much more common than Type I diabetes and is often called "insulin resistance." In cases of Type II diabetes, the body still produces insulin, but the insulin it produces cannot properly connect with fat and muscles to allow glucose inside the cells to produce energy.