Among more than 600,000 U.S. adults, researchers found that those who used electronic cigarettes were more likely to have prediabetes than people who'd never vaped or smoked.
The link was seen even among e-cigarette users who said they had never smoked traditional cigarettes.
Prediabetes refers to blood sugar levels that are higher than they should be, but not yet at the threshold for diagnosing type 2 diabetes.
And research has shown that nicotine, as well as chemicals in tobacco smoke, can alter the body's ability to control blood sugar.
E-cigarettes also contain nicotine, along with their own blend of "e-liquid" chemicals whose effects are not yet fully understood.
E-cigarettes work by heating a liquid that contains nicotine and other substances, like propylene glycol, glycerol and flavoring.