The mix can strike at any age, and comes in various forms: Children who depend on insulin injections because of Type 1 diabetes gain weight and then get the Type 2 form in which their bodies become insulin resistant, for example.
Or someone with classic Type 2 symptoms isn't responding to therapy, and tests reveal they also are developing the insulin-dependent form of the disease. Or they may not fall clearly into either category.
The labels are important — different forms require different treatments.
Yet "there are many people in which it's very blurred as to what kind of diabetes they have," says Dr. Francine Kaufman, a University of Southern California pediatric endocrinologist and past president of the American Diabetes Association.
There are no good statistics on this complex disease-mixing.
But the Children's Hospital of Pittsburgh counts about 25 percent of child patients with Type 1 diabetes who also are overweight and have other Type 2 features, says Dr. Dorothy Becker, a pediatric endocrinologist and leading double-diabetes researcher.
And an ongoing study to determine the best treatment for child Type 2 diabetics is uncovering many participants who harbor antibodies that signal they have or are developing the Type 1 form, too, says Kaufman.
Those findings echo a handful of recent research reports raising concern about the phenomenon, which some call atypical diabetes or "diabetes 1 1/2" or even Type 3 diabetes.
Diabetes occurs when the body can't turn blood sugar, or glucose, into energy, either because it doesn't produce enough insulin or doesn't use it correctly.
With the Type 1 form, the patient's own immune system attacks the insulin-producing islet cells in the pancreas. Once thought to strike only in childhood, it also can develop in adults. Symptoms usually appear suddenly and can quickly become life-threatening. Insulin, given by shots or a pump, is required to survive.