New to freestyle libre 2

[Sadsac@21]

I have just received my freestyle libre 2 today. I’ve put it on and the readings are quite a bit lower than what I was expecting. I usually read between 6.5-10 using the finger prick method. The monitor is reading at 4.5 so I ate something and it went up to 6.2. I tested it using my normal method and it read 10.2.
Why is there so much difference? Which one do I believe?

 

[Rachox]

I find the Libre somewhat inaccurate for the first 24 - 48 hours while it settles in. I try to place a new one the day before the current one is due to run out. I wouldn’t be worrying about a reading of 4.5 as I take no meds which could cause hypos. Maybe check with a finger prick next time you get an unexpectedly low reading?

 

[Deleted member 527103]

When there is a significant discrepancy, the advice is to take the finger prick reading.
It is important to understand the limitations of CGMs like Libre and without doing so, you will find it incredibly frustrating.
These limitations have been repeated many many times on the forum. But in summary (as much as I can remember), these include
- insertion trauma - our body can react to having an alien object in our arm and can taker a day or so to get used to it. In the meantime, the readings can be erratic and is the reason why many of us insert our sensors the day before we activate them. This could be your issue.
- compression low - when pressure is applied to a sensor, it can block the flow of interstitial fluid (what the sensor measures) to the filament resulting in a false low reading. This is most common at night when you lie on your arm in your sleep.
- ISR delay - changes to BG are reflected in interstitial fluid readings (ISR) about 15 minutes later. Libre accommodates this delay by extrapolating the current trend. This is usually ok unless the trend changes direction in the last 15 minutes. The can result in a higher or lower reading at that time.
- Abnormal range - CGMs are designed to be most accurate at "normal" BG which is about 4 to 10 mmol/l. Outside of this range, the sensor can over report highs and under report lows.