To understand diabetes, it is important to first understand the normal process of food metabolism. Several things happen when food is digested:

A sugar called glucose enters the bloodstream. Glucose is a source of fuel for the body. An organ called the pancreas makes insulin. The role of insulin is to move glucose from the bloodstream into muscle, fat, and liver cells, where it can be used as fuel. People with diabetes have high blood sugar. This is because their pancreas does not make enough insulin or their muscle, fat, and liver cells do not respond to insulin normally, or both.

Type 1 diabetes is usually diagnosed in childhood. The body makes little or no insulin, and daily injections of insulin are needed to sustain life.

Type 2 diabetes is far more common than type 1 and makes up most of all cases of diabetes. It usually occurs in adulthood. The pancreas does not make enough insulin to keep blood glucose levels normal, often because the body does not respond well to the insulin.

Type 2 diabetes is becoming more common due to the growing number of older Americans, increasing obesity, and failure to exercise. Gestational diabetes is high blood glucose that develops at any time during pregnancy in a woman who does not have diabetes. Diabetes affects more than 20 million Americans. About 54 million Americans have prediabetes. There are many risk factors for diabetes, including:

A parent, brother, or sister with diabetes Obesity Age greater than 45 years Some ethnic groups (particularly African Americans, Native Americans, Asians, Pacific Islanders, and Hispanic Americans) Gestational diabetes or delivering a baby weighing more than 9 pounds High blood pressure High blood levels of triglycerides (a type of fat molecule) High blood cholesterol level Not getting enough exercise The American Diabetes Association recommends that all adults over age 45 be screened for diabetes at least every 3 years. A person at high risk should be screened more often.