First regarding any reading as completely accurate leads to madness!
As we have discussed before blood glucose meters can be 20% at least out so a reading of 180 could be 216 or 144 if compared to the reading at your clinic visit. Best use a Contour Next where a reading of 180 is likely to be between 171 and 189.
Libre claims to be accurate to about 9% so should be between 162 and 198.
My experience with 18 months of the 14 day UK one judged against the Contour Next is that over 180 it reads up to 20% high and at 72 it reads at least 10% low. But not entirely consistent as my current one is low at all levels.
Memory suggests that somewhere I have read that accuracy figures are based on readings between 72 and 180.
Of course you should try to take readings when you have a straight line for 20 or 30 minutes.
The lag figure I had heard was 7/8 minutes ( a bit tricky to be precise if readings are every 5) I allow for 10. The lag is because the sensor reads the interstitial fluid which gets its glucose from the blood but not instantly.
If you put the Libre on 24 hours before you activate it you should get it up and running without the early wobbles. In my experience it still goes for the full 14 days. If using Xdrip+ with an extra 12 hours.
If you are interested in bg meter accuracy I have an article on my blogsite bgonmywatch.com called “Calibration needs accurate blood glucose meters” that goes in to this in more detail with links to various meter surveys.
The most accurate meter is generally accepted to be the Contour Next with a Mard of around 5. (With Mard the lower number the better) I attach a table showing 17 popular meters in order of accuracy. My practice had prescribed the Jazz before I realized that it was one of the least accurate.
If you are using or are threatened with the US 14 day Libre then I do have an article on the blogsite detailing the competition to produce a transmitter that will will read it satisfactorily.
