In the United States, nearly 1 in 4 young adults (24 percent) and close to 1 in 5 adolescents (18 percent) have prediabetes, according to a new report from the Centers for Disease Control and Prevention.

A CDC official described these numbers as “evidence of a growing epidemic.” Someone with prediabetes has a blood sugar, or glucose, level that is higher than normal but not high enough for a diabetes diagnosis. But health experts say that some of the damaging effects of diabetes – on the heart, blood vessels and kidneys, for instance – can begin with prediabetes.

Although people of any age can develop diabetes, historically it has been more common among middle-aged and older adults. Many with prediabetes have no symptoms, and 90 percent of those who have it don’t know it, according to the CDC, which offers a free online test of your risk for prediabetes and diabetes.

The agency’s new report, based on data collected from 2005 to 2016 from a nationally representative sample of 5,786 people, ages 12 to 34, found that prediabetes was more common among male participants than female and more prevalent among those who were obese than among normal-weight youths and young adults.

In addition, the researchers found that the adolescents and young adults with prediabetes were more apt to have high blood pressure, unfavorable cholesterol levels and other factors that put them at higher risk for cardiovascular disease. Although people with prediabetes often go on to develop full-fledged diabetes, that’s not inevitable. Lifestyle changes – such as more exercise, weight loss and healthier eating – can bring blood sugar levels back to normal.