Diabetes mellitus is a metabolic disorder that interferes with the body's ability to control glucose in the blood. Glucose, a blood sugar derived from the food we eat, is the body's main source of fuel and energy.

Glucose is dependent on insulin, a hormone produced by the pancreas, to enter cells. In normal digestion, the pancreas creates the right amount of insulin to move glucose from the blood to the cells. In people with diabetes, either the pancreas doesn't produce the correct amount of insulin or the body's cells resist the insulin. As a result, glucose builds up in the blood and spills out of the body through urine, depriving the body of its main source of fuel.

Over 20 million Americans have diabetes, according to the American Diabetes Association (ADA).

Type 1
Type 1 diabetes is the form of the disease in which the pancreas produces too little insulin to meet the body's needs. Type 1 diabetes accounts for only 5 to 10 percent of diabetes cases diagnosed in the United States.

Type 2
Type 2 diabetes is the most common form of the disease. People with type 2 diabetes may be able to produce healthy or even high levels of insulin, but their cells are not able to use the insulin effectively. This insulin resistance is often caused by obesity. Many people with type 2 diabetes have a reduced ability to produce insulin, too.

Pre-Diabetes
Most people who develop type 2 diabetes have pre-diabetes first. Pre-diabetes is a condition in which blood glucose levels are higher than normal but lower than the threshold for diabetes. The ADA estimates that 54 million Americans have pre-diabetes.

Without lifestyle changes, many of these people will be diagnosed with type 2 diabetes within 10 years.