Does anyone else Calibrate their CGMs by using the SECOND drop of blood from the same testing site on your finger? I was just watching a Medtronic video where an MD teaches all her patients to use the second drop of blood from the same finger stick…she says that many of the problems todays CGMs having whacky readings is because of the person using the FIRST drop from a stick. She finds using the Second Drop from the same stick gives better calibrations. Heres a link to that video:
This is really about getting the best accuracy from your glucose meter, not about CGM calibration. This study from 2011 found that if you properly washed your hands before checking your blood sugar then the first drop of blood was fine. If you don’t have the opportunity to was your hands then you can improve the results by using the second drop of blood. I try to was my hands before testing.
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I just ran a n=1 experiment using my Accu-Chek Aviva Connect meter. First drop was 115 mg/dl and second drop was 109 mg/dl. I consider these two readings as equivalent due to the meter design.
When I calibrate my Dexcom I take the average of two readings. 115 and 109 average equals 112. My Dex displayed 110 mg/dl.
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For personal experimentation, I have sometimes taken measurements of up to 4 drops from the same prick just to see what variation exists. It’s a fair bit and by no means limited to the difference between the first and second drops, and in this regard I agree it’s a glucose strip+meter issue.
But if I’m measuring for cgm calibration I’ll usually do two or three and average, or throw one out and average the other two depending on how tight the measurements are, just to get the cgm curve calibrated as close to “real” as I can.
I did this once, then I thought well what will i do with the first drop? SO I gave up; the idea. I have filed this one with other good ideas i am ignoring. Like check the air pressure on tires after every stop and do 30 jumping jack every 75 miles.
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I was told to use the second drop as a matter of habit from a coach at Livongo, when I thought I was having a lot of accuracy issues. I am unsure how much of a difference it has made for me, however.