“As for squeezing the finger, the researchers found that too much pressure did appear to interfere with accurate test results. Anywhere from 5 to 13 percent of study participants had a significantly different blood sugar result (versus no squeezing), depending on how much pressure they put on the finger. On average, blood sugar readings were lower when people put pressure on the finger.”
And then I found this:
“squeezing and rubbing your finger after you’ve pricked it can affect the blood sample. “Sometimes you’ll get a little more interstitial fluid [the substance just below the skin] than the capillary blood,” says Lipps.”
I don’t use the tips, for much the same reasons. It hurts like the dickens, and they tend to be tougher. I use the sides of my fingertips, which never got any calluses when I used to still play viola now and then. The skin is thinner to start with and there’s less nerves there as well. I push my thumb against the pad of my finger so the side of my finger bulges out a little bit, and then lance. I’m able to keep my lancing device on the very lowest setting that way. Using the lowest setting has meant that after 15+ years I haven’t really developed calluses from lancing even with testing up to 8-10 times per day. I do exfoliate my hands about once a week and about once a month I’ll use a thick layer of Eucerin on my hands with a pair of white cotton gloves for a couple of hours.
Interesting, but even the researchers note their conclusions should be “interpreted with some caution.” The pressure they used was as follows:
Intervention 4: different external pressures. The participant washed the hands with soap and water and dried them. The cuff of the hand blood pressure meter was put around the middle phalanx of the middle finger. The pressure was increased to 240 mmHg. Immediately, a finger puncture was performed, and the capillary glucose concentration was determined in the first and in the second drops of blood, again wiping the finger with a tissue in between the two drops. Thereafter, the finger cuff was put around the middle phalanx of the ring finger of the same hand. The cuff was inflated to 40 mmHg. A finger puncture was performed after 1 min to achieve venous stasis, and the tests were repeated.
The researchers noted:
A standardized method of squeezing of the finger in daily practice is difficult because the necessity for squeezing varies strongly between individuals, depending on the structure of the skin. A limitation of our study is that the method of squeezing does not fully mimic daily practice, so the results should be interpreted with some caution. The strength of the study is that a standardized method of squeezing was used. The use of one meter by one experienced person limited variability. On the other hand, it limits generalization of the findings to other equipment. There are several aspects that could affect readings, such as the time of the last insulin dosage. Therefore, a separate control measurement was performed for each intervention. The time interval between measurements was maximal 90 s, but in most of the interventions the time interval was 30–60 s. Using this design, it is not likely that these aspects have relevantly influenced the results. However, we cannot completely exclude an effect of this time delay. Multivariate analyses show that in none of the interventions, sex or HbA1c had a statistically significant influence on the results. Finally, because of the selection of the patients, the results cannot be generalized to the hospital setting.
(Bold emphasis added.)
They also noted that another small research study indicated milking the finger gives an accurate sample:
Fruhstorfer and Quarder (13) also investigated the influence of milking the finger in 10 volunteers without diabetes and concluded that milking the finger gives correct glucose values. In our study, we used two pressures to explore whether there would be any influence on the capillary glucose concentration. Venous stasis is achieved with a pressure of 40 mmHg. A pressure of 240 mmHg is above the systolic pressure of the participants. Our study shows more deviation between the glucose concentrations with the higher pressure.
