A recent study published in Diabetes Care investigated whether capillary glucose concentrations, as measured in the first and second drops of blood, differed more than 10 percent when compared with a control glucose concentration in different situations.
In the study capillary glucose concentrations were measured in two consecutive drops of blood in 123 patients with diabetes in the following circumstances: without washing hands, after exposing the hands to fruit, after washing the fruit-exposed hands, and during application of different amounts of external pressure around the finger. The results were compared with control measurements.
The results showed that not washing hands led to a difference in glucose concentration of more than 10 percent in the first and in the second drops of blood in 11 percent and 4 percent of the participants, respectively. In fruit-exposed fingers, these differences were found in 88 percent and 11 percent of the participants, respectively. Different external pressures led to greater than 10 percent differences in glucose concentrations in 5–13 percent of the participants.
Researchers concluded the study with the following recommendation: Wash hands with soap and water, dry them, and use the first drop of blood for self-monitoring of blood glucose. If washing hands is not possible, and they are not visibly soiled or exposed to a sugar-containing product, it is acceptable to use the second drop of blood after wiping away the first drop. External pressure may lead to unreliable readings.