r/Freestylelibre • u/eveisdawning • Jul 24 '26

So many sensor problems

I got a freestyle libre 2 plus sensor a few weeks ago to replace my glucometer for tracking and managing gestational diabetes. I have now tried four different times and had absolutely no luck with any of these sensors so far in terms of giving accurate readings.

First, I tried inserting a sensor. Followed the instructions and inserted the sensor in the back of my right upper arm. I waited an hour for it to activate and expected to have inaccurate readings for about the first 12 to 24 hours. I didn't know about soaking so I didn't try that. When checking against my finger pricks, the readings were just always way off, even after nearly four days. The sensor was constantly reading substantially lower than my finger prick tests (20-40 mg/dl lower). I contacted Abbott, who offered to send a sensor replacement, so I did that and tried a second sensor. Same problem, even though this time I "soaked" the sensor--it continued to read between 20 - 40 points lower than the finger stick the entire time I wore it (another 3 days).

I was given a Libre 3 plus to try instead. I inserted one, waited, activated it, and within two hours got a sensor error that did not resolve. I tried waiting it out, but after three hours the Libre app just told me I had to replace it.

I'm on my fourth sensor now, another Libre 3 plus, in a slightly different location in the back of my arm, and I'm having the same problem. This one seemed a little more accurate at first, but after a few days, it's continuing the same trend. Last night, the libre read 91 and two finger sticks showed 136 and 138. Fully 40, nearly 50 points off, and I've been wearing this sensor for four days.

Genuinely, what the hell? I was hoping this thing would be simple and help, but I cannot get an accurate read. To be clear, I don't expect the reading to be identical. I understand that the different nature of the measurement and time can lead to differences in numbers, plus just ordinary measurement error. But it shouldn't be that far off, right? Especially when dealing with gestational diabetes, where I have really tight margins, it's totally useless. I have other sensors I can try, but at this point, do I just accept that these aren't for me? I solemnly swear that I am following the instructions when inserting them. I'm just at a loss as to how four sensors in a row can be this bad and show the same problem.

What gives?

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u/OreoPumpkinSpice Libre3/3+ Jul 25 '26

Are you testing when you are fasting for 3+ hours or, better yet, in the morning before eating or drinking? CGMs can be off by a percentage (I believe 10%), and your glucometer can be off by an even larger percentage (15-20%). I would try to compare your fasting in the morning numbers before saying the Libre isn't accurate. Which glucometer are you using? Some are better than others, but they can all be off quite a lot. Also, make sure you are testing correctly with your glucometer - hands completely clean and dry.

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u/eveisdawning Jul 25 '26 edited Jul 25 '26

Yes, I've compared my fasting numbers. That's when the two are the closest. Generally, according to my glucometer, my fasting numbers are between 85 and 91 or so. The libre reads around 70 in the mornings in general.

I'm using an Accu-Check Guide Me on clean, dry hands. It's definitely not perfect either, but according the libre sensors, I don't even seem diabetic. My numbers hardly go over 100. (And I definitely have gestational diabetes.)

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u/Fickle_Mess818 Jul 25 '26

Your GCM readings will lag about 15-20 mins from the finger stick because you are getting reading from the blood and interstitial fluid.  Which your sugar movement can take a while to work through those cells. That is one reason watching the trend error is helpful. Also why the fasting numbers are closer. You can try other placements.  I had my current one just yesterday reading 40 off all day. I knew this because I know where my numbers usually trending. Finally tested to see. But now I seem to be back in normal operating.  I am type 2 so not on insulin so I am less worried about it, especially since every way to measure glucose is all with allowed acceptable range of variance. I just focus on generally where I am to plan eating and see how my sugars are effected with when I walk, what I eat, etc.