Blood glucose monitoring is an important part of managing diabetes, but according to a new study in the journal Diabetes Care, failure to take the simple action of washing your hands with water before pricking your finger could result in falsely elevated readings.
Cleaning the finger with an alcohol swab prior to taking a blood sample is commonly recommended as a way to make sure the test site is clean. To determine whether alcohol swabbing effectively removes fruit residue, researchers at the Juntendo University Graduate School of Medicine in Tokyo measured the blood glucose levels of 10 volunteers without diabetes under a variety of conditions. As a control, the participants’ fingers were cleaned and a fingerprick check was conducted to determine their true blood glucose levels. The volunteers then peeled either oranges, grapes, or kiwis, and then had their blood glucose checked immediately, after swabbing with alcohol, and again after washing with tap water.
The researchers found that when the volunteers’ hands were cleaned with tap water, their blood glucose readings matched their readings prior to peeling the fruit, generally around 90 mg/dl. However, when their glucose levels were measured immediately after peeling the fruit, on average their readings shot up to 170 mg/dl after peeling an orange, 180 mg/dl after peeling a kiwi, and 360 mg/dl after peeling a grape, respectively. And even when they had swabbed their fingers with alcohol — in some cases as many as five times — prior to the measurement being taken, the readings still remained elevated over their actual blood glucose level.
In an interview with Reuters, Robert Cohen, MD, an endocrinologist who was not involved in the research, noted that “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.” But, he contends, people “really need to have a checklist” to ensure the most controlled monitoring environment possible and, consequently, the most accurate results possible.
According to the authors, the take-home message is to wash your hands with tap water instead of relying on alcohol swabs before checking your blood glucose — particularly if you have been handling fruit.
To learn more, read the piece “Fruit salad and blood glucose meters don’t mix” or see the study’s abstract in Diabetes Care. And for tips on getting an accurate blood glucose result, check out “Making Your Meter Work for You.”