Type 2 diabetes is by far the most common form. Ninety percent to 95 percent of people beyond age 20 who have diabetes have type 2. Like type 1 diabetes, type 2 used to be called by a couple of other names: noninsulin-dependent diabetes and adult-onset diabetes. These names reflect that many people with type 2 diabetes don't need insulin shots and that the disease usually develops in adults. Similar to type 1, the names aren't entirely accurate. Children and teenagers, as well as adults, can develop type 2 disease. In fact, the incidence of type 2 diabetes in adoles­cents is increasing. In addition, some people with type 2 disease need insulin to control their blood sugar.

Unlike type 1 diabetes, type 2 disease isn't an autoimmune disease. With type 2 diabetes, your pancreas makes at least some insulin, but one or two other problems develop:

• Your pancreas doesn't make enough insulin.
• Your muscle and tissue cells become resistant to the insulin.

When your cells develop a resistance to insulin, they refuse to accept insulin as the key that unlocks the door for sugar. As a result sugar stays in your bloodstream and accumulates. Exactly why the cells become resistant to insulin is uncertain, although excess weight and fatty tissue seem to be important factors. Most people who develop type 2 diabetes are overweight.

Over time some people with type 2 diabetes need more insulin than their pancreases can supply. Like people with type 1 diabetes, they become dependent on insulin medication to control their blood sugar.