Hi, I use a Libra but I've noticed a few times it shows me a reading. I grab my insulin and check again before injecting to find the figure has dropped. For example it showed me I'd been up around 10.8 for 15 mins before my lunch. When I checked after working out my carbs my it says 8.4. and no sign of the high levels in the graph. Is this normal? Should I check with a finger prick?
Libra sensor changing reading
- Thread starter Miss Piggywig
- Start Date
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Well-Known Member
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- Type of diabetes
- Type 1
- Treatment type
- Pump
CGMs like Libre, do not read blood. They read something called interstitial fluid. Changes in BG are reflected as changes in interstial fluid about 15 minutes later.
To overcome this delay, the algorithm that Libre uses to calculate BG from the interstitial fluid readings extrapolates the current trend to “predict“ the current BG reading. When the interstitial fluid has “caught up” with the blood, Libre will correct the prediction.
Most of the time, there is no need for an update. However, if the trend changes, you will notice the value you changes. For example, if your BG was rising and then your insulin kicks in, your BG will start falling. However, Libre will take 15 minutes to work out the change in direction.
You will also see this when your BG stops falling. It is why Libre may over egg a hypo and show longer to recover.
So, to answer your question, this is normal and no need to check with a finger prick unless you think it is wrong,
To overcome this delay, the algorithm that Libre uses to calculate BG from the interstitial fluid readings extrapolates the current trend to “predict“ the current BG reading. When the interstitial fluid has “caught up” with the blood, Libre will correct the prediction.
Most of the time, there is no need for an update. However, if the trend changes, you will notice the value you changes. For example, if your BG was rising and then your insulin kicks in, your BG will start falling. However, Libre will take 15 minutes to work out the change in direction.
You will also see this when your BG stops falling. It is why Libre may over egg a hypo and show longer to recover.
So, to answer your question, this is normal and no need to check with a finger prick unless you think it is wrong,
Thank you this is really helpful information. Only a month in so I'm still learning lots. This forum and all you lovely people are keeping me sane at the moment.
