Atlanta ? As many as 1 in 3 U.S. adults could have diabetes by 2050, federal officials announced Friday in a dramatic new projection that represents a threefold increase.

The Centers for Disease Control and Prevention estimate that 1 in 10 have diabetes now, but the number could grow to 1 in 5 or even 1 in 3 by mid-century if current trends continue.

“This is alarming,” said Ann Albright, director of the CDC’s Division of Diabetes Translation.

The agency’s projections have been a work in progress. The last revision put the number at 39 million in 2050. The new estimate takes it to the range of 76 million to 100 million.

An estimated 24 million Americans have diabetes currently.

The new CDC calculation accounts for people who have diabetes but are undiagnosed — a group that wasn’t figured into earlier estimates, explained Edward W. Gregg, chief of the CDC branch that handles diabetes epidemiology and statistics.

Also, the researchers used new population growth estimates for the elderly and minorities, who have higher rates of Type 2 diabetes, he said.

One more factor: Diabetics are living longer, thanks to improvements in medical care, he added.

“Not all of the increase in prevalence is a bad thing,” said Dr. Sue Kirkman, the American Diabetes Association’s senior vice president of medical affairs and community information.