And if the peelers swabbed their finger with alcohol in between peeling and finger pricking, the readings were still higher than normal. Even swabbing five times didn’t produce correct results.

In the directions that come with blood sugar meters, the manufacturers generally tell users to wipe their finger with an alcohol swab before taking a reading. But that might not always do the job, the researchers say.

“People are used to pricking the finger, drawing a blood sample, (and) assuming that the measurement they make reflects the sugar content in the blood,” said Dr. Robert Cohen, who studies diabetes at the University of Cincinnati Medical Center and was not involved in the current research.

But, he told Reuters Health, patients “really have to have a checklist” that helps them decide, Was the test done right? Are the circumstances right for this?

Cohen said the example in this study may seem obvious: having sugar on your fingers from fruit can interfere with that meter’s readings. But it’s still an important finding, he said.

When you use the meters, Cohen said, the assumption is that you’re measuring your blood sugar, not the sugar on your fingers.

Getting an inaccurate reading from sugar on the outside of the finger “could lead somebody to take insulin when they don’t need it,” Cohen said. “They could run the risk of running a low sugar from having misleading data.”

The message, the authors say, is to wash your hands before using a blood sugar meter and not rely on alcohol swabs, especially if you’ve been handling any fruit.

SOURCE: Diabetes Care, online January 31, 2011