Blood Sugar Meters: The Number One Mistake

Accuracy counts when you measure your blood sugar, so it's crucial that you wash your hands thoroughly just before testing. That's because even microscopic pieces of fruit on your hands could skew the results of your finger prick blood test, causing your level to appear higher than it really is, a study shows.

Researchers for the study, which appeared in the journal Diabetes Care and was reported on Reuters Health, focused on 10 healthy volunteers, none with diabetes. The scientists, from the Juntendo University Graduate School of Medicine in Tokyo, Japan, recorded the volunteers' blood sugar levels under various conditions.

They learned that when the study participants tested their blood sugar right after peeling fruit, their blood sugar levels skyrocketed. The study showed that the blood sugar went up to 170 mg after peeling an orange, 180 mg after peeling a kiwi, and 360 mg after peeling a grape. Swabbing the finger with alcohol didn't help much. Even when participants swabbed their fingers five times, the blood sugar readings were still higher than normal.

To prevent this from happening, it's crucial to test when you have clean, dry hands, says Devon Carlson, MS, RD, of the Naomi Berrie Diabetes Center at NewYork-Presbyterian Hospital/Columbia Medical Center in New York City. "And the inaccurate results don't just happen with fruit," she says. "It can also happen with other carbohydrates."

Fruit isn't the only culprit when it comes to getting an inaccurate blood sugar level, agrees Spyros Mezitis, MD, of Lenox Hill Hospital in New York City.

"We tell our patients to not be exposed to anything sweet before they test," he says. "If you touch sweet foods, then you get a sugar layer on your hands and it takes a little time for that to come off."

If you have access to a sink, wash your hands in warm, soapy water, Carlson says. If you're on the go, using an alcohol swab is okay, but using alcohol to test every time is not a good idea since it can dry out your fingertips, Carlson says.

Realistically, getting a high blood sugar from handling sweet foods may not happen very often, Mezitis says. "People tend to check their blood sugar before they eat and then two hours after they eat," he says. "The danger is that if you test your blood sugar and think it's high when it's not, you will give yourself insulin even when it's not needed."

A related problem can develop if your hands are wet when you test, says Carlson. If this happens, you may get a falsely low blood sugar reading. 

Carlson stresses that the study shouldn't have diabetics avoiding fruit, a good source of fiber and vitamins. It simply means they should take precautions not to handle it just before they test their blood sugar.

The best way for diabetics to eat fruit is to enjoy it with protein. "Pair it up with a source of protein, like some cheese or nuts, and it will slow down the digestion so your blood sugar won't get so high," Carlson suggests.




Pittman, Genevra. Fruit salad and blood sugar meters don't mix. 9 February 2011. Reuters Health.