Type 2 diabetes is a condition in which the body resists the insulin that is produced by the pancreas and may fail to make enough insulin to maintain normal glucose (blood sugar) levels. It is by far the most common form of diabetes.

About 19 million Americans, many of them undiagnosed, have type 2 diabetes, according to the National Institutes of Health. The incidence of type 2 diabetes has soared in the United States and worldwide in recent years, largely because of growing rates of obesity.

The exact cause of type 2 diabetes is unknown. However, it is associated with certain factors, including obesity, lack of exercise, age, a family history of diabetes, ethnicity and a history of gestational diabetes. Those at risk of developing this form of diabetes can prevent or delay the onset of the disease by achieving a healthy weight, eating a healthy diet and exercising more.

The symptoms of type 2 diabetes develop slowly. They may include fatigue, blurry vision and increases in hunger, thirst, urination and infections. Sometimes people have only mild symptoms or none at all. It is not uncommon for a person to have type 2 diabetes for years before being diagnosed through a glucose test.

Diabetes increases a person’s risk of developing serious complications, including nerve, eye, kidney and blood vessel disease. Treatment, including a combination of diet and exercise and sometimes insulin or antidiabetic agents, can control glucose levels and prevent or delay the onset of many of these complications.