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Freestyle libre 2 / finger prick.

KirstyRobbie

KirstyRobbie

Active Member
Hello,

Does anyone know why my freestyle libre2 measures my glucose levels completely different to the finger prick machine? As in this morning it scanned at 6.5 yet when I tested with a finger prick it was 10.1, and just now I scanned at 5.5 yet the finger prick was 7.1?

I’m a type 2 ( for 7 years) and am monitoring my sugars as much as possible currently as my recent hba1c was high (69) and they want to try me on new meds ( currently SL metformin)

I am following a low carb diet the best I can. And I got the freestyle on the free 2 week trial to use out of interest. Just I am very confused in the massive difference in readings and do not know which is the incorrect/correct reading I am getting?

Thank you. X
 
KirstyRobbie said:
Hello,

Does anyone know why my freestyle libre2 measures my glucose levels completely different to the finger prick machine? As in this morning it scanned at 6.5 yet when I tested with a finger prick it was 10.1, and just now I scanned at 5.5 yet the finger prick was 7.1?

I’m a type 2 ( for 7 years) and am monitoring my sugars as much as possible currently as my recent hba1c was high (69) and they want to try me on new meds ( currently SL metformin)

I am following a low carb diet the best I can. And I got the freestyle on the free 2 week trial to use out of interest. Just I am very confused in the massive difference in readings and do not know which is the incorrect/correct reading I am getting?

Thank you. X
Click to expand...
As I understand it the fingerprick measures glucose in blood but the Libre measures what's in the interstitial fluid, so they are likely not to be the same. I haven't much experience with a Libre - just the free trial - but noticed that the readings never coincided. The best I could hope for was a standard and predictable error. I found the Libre tended to read higher than the fingerprick, sometimes quite a bit higher.
 
i find that the Libre is always lower than a finger prick this is normal for me the readings are very rarely the same for reasons previously stated , the libre reading is about 10 mins behind an actual finger prick
 
Suspect finger prick is more accurate ... cgm/flash glucose monitors are good for trends and finding out what happens overnight. GP might be interested in both ...
 
KirstyRobbie said:
Hello,

Does anyone know why my freestyle libre2 measures my glucose levels completely different to the finger prick machine? As in this morning it scanned at 6.5 yet when I tested with a finger prick it was 10.1, and just now I scanned at 5.5 yet the finger prick was 7.1?

I’m a type 2 ( for 7 years) and am monitoring my sugars as much as possible currently as my recent hba1c was high (69) and they want to try me on new meds ( currently SL metformin)

I am following a low carb diet the best I can. And I got the freestyle on the free 2 week trial to use out of interest. Just I am very confused in the massive difference in readings and do not know which is the incorrect/correct reading I am getting?

Thank you. X
Click to expand...

The Freestyle Libre readings are usually around 20 mins behind your actual blood readings. So if your finger prick was 10.1, around 20 minutes later your Libre should have said you were approximately 10.1 also.

If you still see a big difference even accounting for that 20 minute difference, it is quite possible your Libre 2 is faulty (which happens often). Simply contact Abbot, they'll probably want 3 different samples of reading discrepancies between your finger prick and the Libre, and they will send you a new one.

Remember even your finger prick reader has a 15% accuracy range, none of the numbers are actually fully accurate. The Libre 2 is great to see trends and spikes rather than relying on it for absolute numbers, but it shouldn't be so inaccurate as you are describing.
 
I'm so interested in this as I am currently using Libre 2 for a month (can't afford to continue afterwards) and my readings on the libre have been high in comparison to the finger prick. For instance, my Libre says 8.7 right now and the finger prick says 7.6. What would you assume to be most accurate?
 
As a long term Libre1/2 user I have found that they are very variable, but usually read low.
In fact it is a bit of a shock when one turns out to be accurate.
Finger prick should be more accurate but the strength of the Libre is the continuous monitoring.
 
SheilaCanning said:
my Libre says 8.7 right now and the finger prick says 7.6. What would you assume to be most accurate?
Click to expand...
It's impossible to say, they both have a margin of accuracy the finger prick meters are +/-15%, no idea what the Libre is but I would imagine something similar.
No form of home testing is as accurate as you would get in a laboratory, the best we can hope for is to have some idea of what range our glucose is in
The difference in your two methods of testing Is just 1.1mmol/L so I would think that you can say with some certainty that your blood sugar is in the range of 7 to 9 mmol/L, and that both the Libre and your meter are performing well.
 
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