I’m currently using a Johnson & Johnson One Touch® Ultra glucometer. Most days I check my blood sugars in the morning when I get up and in the evening before I eat dinner. Sometimes when I think a reading is too high, I’ll immediately do another and sometimes the reading is even higher, but most often it is lower, as much as fifty points lower. Just how accurrate are glucometers supposed to be?
Your meter came with a control solution, which you should use periodically to make sure everything is calibrated correctly. Run a test using the control solution and compare this reading with the range that is printed on your vial of test strips.
If the control solution test is not within range, or if you continue to have unusual test results, you should call the number printed on the back of your meter and discuss it with a customer service representative (available 24/7). If they believe there is a problem with your meter, they’ll probably send you a new one next-day air.
The One-Touch Ultra received the highest score in the October 2001 edition of Consumer Reports, which included tests of both meter accuracy and precision.
I don’t know how accurate that meter is supposed to be, but I asked about a similar meter and was told that its precision was only around +/- 20% (95% confidence).
Remember too that even if you think your fingertips are clean, they may not be. I’ve seen a false high more than 100 points higher from having sugar-containing residue on a finger.
Also note that even a small amount of water, or alcohol, left on there can skew a reading to the low side too.