so have started using Libre 2 this week so far so good, but i had a bit of a shock alarm this morning at 1am when blood alarm went off at 3.8 … is it normal for levels to drop that low at night .. on 500 metformin once a day .. woke up to BGL of 5.6 .. i am now worried
CGM Alarm !!!!
- Thread starter Nixterjoe
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Were you lying on the Libre arm when the alarm went off? Libres often record a low when squashed. Also you need to check the reading with a finger prick test. It is extremely unlikely to have a serious hypo on Metformin.
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ok great thank you .. not happened before but will take my blood monitor to bed tonight just in case
CGMs such as Libre are great pieces of kit IF you understand their limitations. Sadly, Abbott (or any other CGM manufacturer) does not share these limitations but they are mentioned again and again and agin on the forum.
If you fail to understand these limitations, you will find your CGM very frustrating and a waste of time, money and brain power.
One of these limitations has already been mentioned: compression lows. If you apply pressure to a sensor, it will report a false low.
Others include:
- Insertion trauma. Some of us find our bodies react to the appearance of an alien object in our arm and can take a day or so to get used to it. This affects readings from the CGM over that time. This is why it is common to apply a new sensor a day or two before activating it.
- Outside normal range. CGMs are designed to be most accurate at "normal" levels (about 4 to 8mmol/l). Outside of this range, the readings can exaggerate the highs and lows. This is why it is recommended to check highs and lows with finger pricks
- Interstitial fluid delays. CGMs read interstitial fluid not blood. It uses an algorithm to convert this to BG. Changes to BG can take 10 to 15 minutes to be noticed at the Interstitial fluid. The algorithm Libre applies takes this into consideration by extrapolating the current trend. Therefore you do NOT need to compare a finger prick with a Libre reading 15 minutes into the future UNLESS the trend of your readings has changed direction in the last 15 minutes.
- Inaccuracies and errors. Unfortunately, some sensors are less accurate or faulty. If you constantly find readings at "Normal levels" when your BG is not changing fast is out by a high percentage (the accuracy is considered as a percentage not an absolute number), you should report this to Abbott NOT by email but either by calling their support team or completing the online form. In most cases, they will replace the sensor, They may ask you to return your sensor in a BIOSAFE envelope (which they provide) so don't throw your faulty one away.
If you fail to understand these limitations, you will find your CGM very frustrating and a waste of time, money and brain power.
One of these limitations has already been mentioned: compression lows. If you apply pressure to a sensor, it will report a false low.
Others include:
- Insertion trauma. Some of us find our bodies react to the appearance of an alien object in our arm and can take a day or so to get used to it. This affects readings from the CGM over that time. This is why it is common to apply a new sensor a day or two before activating it.
- Outside normal range. CGMs are designed to be most accurate at "normal" levels (about 4 to 8mmol/l). Outside of this range, the readings can exaggerate the highs and lows. This is why it is recommended to check highs and lows with finger pricks
- Interstitial fluid delays. CGMs read interstitial fluid not blood. It uses an algorithm to convert this to BG. Changes to BG can take 10 to 15 minutes to be noticed at the Interstitial fluid. The algorithm Libre applies takes this into consideration by extrapolating the current trend. Therefore you do NOT need to compare a finger prick with a Libre reading 15 minutes into the future UNLESS the trend of your readings has changed direction in the last 15 minutes.
- Inaccuracies and errors. Unfortunately, some sensors are less accurate or faulty. If you constantly find readings at "Normal levels" when your BG is not changing fast is out by a high percentage (the accuracy is considered as a percentage not an absolute number), you should report this to Abbott NOT by email but either by calling their support team or completing the online form. In most cases, they will replace the sensor, They may ask you to return your sensor in a BIOSAFE envelope (which they provide) so don't throw your faulty one away.
