TUESDAY, Dec. 1, 2015 (HealthDay News) -- Metformin is the standby drug for millions of people with type 2 diabetes, but a new study finds that adding it to insulin therapy won't boost blood sugar control for overweight teens with type 1 diabetes.
In type 1 diabetes, which comprises about 5 percent of diabetes cases, the body is unable to produce the insulin it needs. So, supplemental insulin is a must for people with the disease.
The new study was led by Kellee Miller of the Jaeb Center for Health Research in Tampa, Fla. As her team explained, young people with type 1 diabetes are at even higher metabolic risk if they become overweight or obese, especially in adolescence.
That's because both obesity and puberty may cause the patient to require higher levels of supplemental insulin, complicating blood sugar control, the researchers said.
Metformin -- a pill taken to help lower blood sugar -- is widely used to treat type 2 diabetes. However, prior studies of how it might affect blood sugar control in teens with type 1 diabetes have been inconclusive, Miller's team noted.
The new study involved 140 overweight and obese patients ages 12 to 19 with type 1 diabetes. Each was randomly assigned to take either metformin or a placebo, along with their insulin, for six months.
The result: Patients taking metformin showed no improvement in blood sugar (glycemic) control over those taking the placebo. A small beneficial effect from the metformin was seen early on in the study, but it disappeared as the weeks went on.
Furthermore, patients who took metformin had more gastrointestinal side effects than those who didn't take the drug, Miller's team said.
"These results do not support prescribing metformin to adolescents to improve glycemic control," the researchers wrote in the Dec. 1 issue of the Journal of the American Medical Association.
One expert in diabetes care said there could still be a role for metformin for these patients, however.
Dr. Spyros Mezitis is an endocrinologist at Lenox Hill Hospital in New York City. He pointed out that the addition of metformin did seem to offer patients some benefits.
"Metformin did decrease the amount of insulin used and was associated with weight loss," Mezitis said, although it "did not reduce blood pressure or cholesterol profiles."
Metformin is also known to cut glucose production by the liver, curb harmful insulin resistance and reduce appetite, he added.
So, "I think more randomized trials are needed before practicing physicians change their practice of using metformin in adolescent overweight type 1 diabetic patients," Mezitis concluded.
The American Diabetes Association has more about type 1 diabetes.