In fact, they report in the journal Diabetes Care, people at the high end of what's considered the normal blood sugar range are twice as likely to get the disease as are those in the low end.
But does that mean doctors should treat these people any different, as the researchers suggest? Not at all, said one expert who wasn't involved in the new work.
"The concern here is that people get started on medications at a level below the conventional threshold for diabetes," Dr Michael LeFevre, a family physician at the University of Missouri in Columbia, said.
"My personal recommendation is that people should strive to manage their weight and be physically active irrespective of what their blood (sugar) level is," he added.
Type 2 diabetes is a lifestyle disease in which the body no longer responds appropriately to the hormone insulin, which helps ferry sugar from the blood into our cells after a meal.
When fasting blood sugar levels reach 126 milligrams or more per decilitre, doctors will diagnose diabetes, because too much sugar in the blood will cause severe damage to the heart, kidneys and other organs over time.
Traditionally, blood sugar levels below 100 milligrams per decilitre have been considered safe, whereas levels between 100 and 126 signal a higher risk of diabetes - termed pre-diabetes.
But according to the new study, by Dr Paolo Brambilla and colleagues at the University Milano Bicocca in Italy, the currently accepted "normal" blood sugar range might be too wide.
The researchers looked at data for nearly 14,000 men and women who'd had blood drawn several times at their clinic.
The patients were between 40 and 69 years old and all of them had normal blood sugar levels at first. Over the next seven to eight years, on average, about 2% of the women and nearly 3% of the men developed diabetes.
Less than 1% of those who started out with fasting blood sugar levels between 51 and 82 milligrams per decilitre wound up with the disease, while more than 3% did so if they had values between 91 and 99.
After controlling for other factors that might influence the likelihood of getting diabetes, that corresponded to a two-fold difference in risk of developing the disease.
The findings are in line with an earlier study from Oregon, and the Italian researchers say they can help identify the people who need extra medical attention.
According to the American Diabetes Association, more than 25 million people in the US have diabetes, and as many as 79 million have pre-diabetes.
But LeFevre, who's a member of the US Preventive Services Task Force, a federally supported expert panel, said he was concerned about the label "pre-diabetes" - let alone expanding its downward into lower blood sugar ranges.
"We don't know that there is a magic threshold" for blood sugar, he said. "As the blood sugar goes up, the risk of complications increases."
Unless you're diabetic, he said, the best thing to do is to eat a healthy diet and get lots of exercise. And that goes for people with low blood sugar as well.
"I would be very concerned if people with low (blood sugar) levels would allow themselves to be sedentary and overweight as a result of these findings," LeFevre said.(Reuters Health/ May 2011)