Libre Vs Finger Prick

The advice I was given when I trialled the Libre was that it does not replace finger pricks: it supplements them.
The huge benefit of the Libre is to detect trends.
I was told I should not use it for calculating insulin doses and it is not allowed to use to test BG before driving.

The Libre uses a different mechanism to calculate BG - for a start, it doesn't use blood; it uses interstitial fluid. This gives a reading which is, typically, 15 minutes behind finger pricks (from blood).

Some people find the Libre incredibly close to finger pricks or consistently out by the same amount so they can always add a certain amount to the Libre readings.
Others find it less accurate. Unfortunately, I am one of these people. This may be because my BG changes quickly when I eat or when I exercise.
I also find the readings become less reliable the longer I have the sensor in. The sensor is less likely to be able to provide a reading over time: I suspect this is because with all my exercise, the little wire sensor has started to move around even though the transmitter part is firmly attached to me.

So, to answer your question: I have never experienced a change in accuracy over time.
But you should not be relying on the Libre anyway.
The trends should remain pretty much the same.

Yes I have! The last sensor was spot on for 10 days (15 mins apart) and erratic the last 4. I agree with @helensaramay the little wire sensor has shifted. Or as In my case the allergic reaction and subsequent itching I get has affected its ability. I’ve worn a fair few, they are all different and I never correct with insulin or food without first doing a finger prick.

I've just had similar on my current sensor (it shows me as in range when I'm too high and LO when I actually do get a hypo) after the first week. It's anywhere between 3-6mmol/L out at different times right now. Abbott are replacing this one for me.

EllieM said:

My feeling is that it was a mistake for Abbott to opt to NOT calibrate the libre against actual blood sugars (unlike dexcom). It means that people whose bodies are outside the norm don't get usable results.

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Makes sense although conversely Dexcom has moved away from calibration with the G6 now so may land in a similar situation with some people.

Closer than daxcom that has to be said daxcom can be way out. G5 anyway. Not sure I even want to try the g6. When I actually remember to order a free style I rarely blood test unless I feel low and it saying I am a bit low. (Hope that makes sense)

EllieM said:

I believe it still allows the option to calibrate? (I hope so, because I am currently considering self funding, and given my libre experience I doubt dexcom would be any better without self calibration... Though in any case, I'm in NZ, and I don't think the G6 will be available for a while).

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If you have to calibrate every 12 hours why bother with it? You might as well just do 3 tests a day.

Hi @nyad21

I’ve been using the Libre for over a year. I’ve had one sensor that started to “fail” in the last few days of its 14 day life; probably because it was becoming loose. I think it’s more likely in the current hot weather when we’re more likely to sweat and so the adhesive may not last so long.

I (and many others) cover my sensors with a (transparent) Tegaderm 6x7cm dressing. They’re about 50p each from the chemists and stop sensors being accidentally knocked off.

I was finger sticking 5 times a day. So I appreciate the sensor. However, one of my sensors gave very low readings for all scans. They were 60% to 90% lower than my test strips. It could have been sensor placement or it could have been a defective sensor. Either way, the people at Libre replaced it but did not seem to be all that concerned about the situation. They seem to write off any comment that could make their product look bad.

Every sensor should have a 5 test strips included just for testing/verifying.

cxl0702 said:

If you have to calibrate every 12 hours why bother with it? You might as well just do 3 tests a day.

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Because for good control 3 tests a day is not enough.

I must be one of the lucky one's. I have never had a drop off in readings nor have the readings between the Libre and finger testing been widely different and I have been using it for well over two years now.

I have been using the libre for the last year, I find it very close to my finger blood tests if I allow 15 to 20 minutes before doing the finger blood test, I have had 2 faulty sensors because of the heat and then knocking the Senser, I may go onto the minimed 670g with sensers soon, so then I can see which is best found the minimed 640 g with senser a lot more trouble, although I like the minimed 64og on its own

cxl0702 said:

If you have to calibrate every 12 hours why bother with it? You might as well just do 3 tests a day.

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It's more like not having to test between 11 and 15 times a day anymore, and less hypo's and better bg as well!

nyad21 said:

My partner is Type 1, diagnosed 7 months ago aged 44. He has been using the Libre and is due to change it tomorrow. His levels have been mostly consistent with finger pricks until the last 2 days when they are 4-5 points out. Has anyone else experienced this? We are hoping the problem will resolve when we change it tomorrow, but are nervous to trust it now...

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There is a .4 difference usually with the finger prick (blood sugar) consistently higher than the sensor (interstitial fluid). I'm a type 1 brittle diabetic who is asymptomatic to hypos. The sensor is great for relieving my fingertips from endless stabbing! I had paramedics out three days ago and the Libre sensor showed low while my blood sugars showed 11.4. Discrepancies like this are dangerous so be careful. Blood sugars are always more accurate. Good luck

I found that it was accurate if my BG was between 5 and 8. If I was higher than this the readings were often way out and add I relied on them I would have massively over-corrected. BG of 9 sometimes gave be readings of 17! When I was in the low 4’s I would get readings below 3, and it wasn’t because my body had reacted to a hypo and the Libre was 15 mins behind - I was doing BG every 15 mins just to test it so I knew that no hypo had occurred.
As another poster has said, it is great to spot trends. I went to bed at 5 and woke up at 5 but what I hadn’t realised before the Libre was that I was rising in the early part of the night and then falling back before I woke (over-compensating for the dawn phenomenon).
If you are self funding, it may be worth looking at the Dexcom G6, which has recently launched, and is believed to be much more accurate. If you search for it, the launch can be viewed on You Tube. Based on their prices it is slightly more expensive but forums say that the transmitter lasts much longer than advertised so the cost is less as they are replaced less frequently.

OK, how do I reconcile this one?

I just received my new Libre test strips.
I have about 30 of my Breese2 test strips left.
I have a working Libre sensor in place for 2 days now.

I did a finger stick, and from the same drop of blood, I measured using both the Libre test strip and the Breeze2 test strip.
The reading on my Breeze2 meter/test strip is 204.
The reading on my Libre meter/test strip is 177.
However, the reading on the Libre sensor is 177.
All readings were taken within 30 seconds of each other.

Isn't there some discussion about a 15 minute delay or something?
Granted, this is only the first observation but it is very interesting the the sensor measured exactly the same as the Libre test strip yet the Breeze2 measurement is 13% off, no?

TTKMAWAN.....

andi140373 said:

I found that it was accurate if my BG was between 5 and 8. If I was higher than this the readings were often way out and add I relied on them I would have massively over-corrected. BG of 9 sometimes gave be readings of 17! When I was in the low 4’s I would get readings below 3, and it wasn’t because my body had reacted to a hypo and the Libre was 15 mins behind - I was doing BG every 15 mins just to test it so I knew that no hypo had occurred.
As another poster has said, it is great to spot trends. I went to bed at 5 and woke up at 5 but what I hadn’t realised before the Libre was that I was rising in the early part of the night and then falling back before I woke (over-compensating for the dawn phenomenon).
If you are self funding, it may be worth looking at the Dexcom G6, which has recently launched, and is believed to be much more accurate. If you search for it, the launch can be viewed on You Tube. Based on their prices it is slightly more expensive but forums say that the transmitter lasts much longer than advertised so the cost is less as they are replaced less frequently.

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Thank you for the information. CCG have just started funding the sensors and monitors. I'll make sure I feed back though.

Hi @Gork

Meditronics produced this video to explain why Sensor Glucose Monitors (measuring interstitial fluid glucose such as the Libre) have different readings to Blood Glucose Monitors (finger prick tests):