A new government estimate shows that nearly 1 in 3 U.S. teens have prediabetes, putting them at risk for Type 2 diabetes and other serious health problems.

In a new analysis, the U.S. Centers for Disease Control and Prevention (CDC) says about 8.4 million 12- to 17-year-olds were prediabetic in 2023. That’s far more than the 18% estimate published in a 2020 scientific paper, The Associated Press reported.

The number is higher in part because the CDC used a new method to calculate the data. 

But that change has raised concerns among experts who say the agency hasn’t shared enough information about how it arrived at its estimate.

The new findings were posted in a 600-word online summary, not in a peer-revewed journal or the CDC's Morbidity and Mortality Weekly Report, The AP said.

The new analysis used data from the National Health and Nutrition Examination Survey (NHANES), which includes lab tests, interviews and health exams.

Melissa Dibble, a CDC spokesperson, said the update relied on “the latest science and technologies” to reflect how research is changing over time.

“These new data highlight the magnitude of prediabetes among adolescents and serve as a critical wake-up call for the nation,” Dibble said in a statement.

But experts say the lack of detail about how the numbers were calculated is troubling. 

“For any of the national health organizations now being decimated by firings (and) layoffs, I am going to be skeptical of data updates until there is transparency and clarity on the source of the data and analysis,” Christopher Gardner, a nutrition and diabetes expert at Stanford University, told The AP.

Prediabetes means that blood sugar levels are higher than normal but not high enough to be Type 2 diabetes.

While some teens may regain normal blood sugar levels after puberty, many do not — and the condition puts them at risk for heart disease, stroke and diabetes later in life.

“It’s still a call to action,” said Dr. Samar Hafida, an endocrinologist with the American Diabetes Association (ADA). “There will likely be a surge in early onset Type 2 diabetes that we are not prepared to deal with.”

The ADA recommends screening children for diabetes starting at age 10 if they are overweight or have another risk factor.

The new estimate shows that if the updated method had been used on the 2005-2016 data analyzed for the 2020 paper, the estimate would have been about 28%, not 18%.

So the jump to 33% may not reflect a huge real-world increase, The AP said.

Still, some experts say the CDC should have shared more details to help the public understand the numbers.

“I would like to believe it doesn’t diminish the quality of CDC data,” Steven Kahn, a diabetes expert and editor of Diabetes Care, said.

“However, because there’s no raw data to look at, none of us can look at it to better understand where these numbers are derived from and what they really mean,” he added.