Libre not accurate

I was finally given a box full of libre devices by my new ENDO. I started using one of the devices and it extremely excited about it. I quickly began to notice how grossly inaccurate it has been in comparison to my blood meter. The libre stated I was 75 mg/dl and when I checked with my blood meter it stated I was 120 mg/dl. I didn’t notice a change in my body that I would normally get when I am under 100 mg/dl.

I have noticed the same inconsistencies for the past few days. Is this normally? Am I missing something?

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I’ve heard that with the Libre but even worse.
Some people do better on it than others.
I have had dexcom sensors go wildly inaccurate.
Like it would read 50 mg/dl but a fingerstick says 160

No system is perfect, but I am generally happy with dexcom sensors


And don’t forget, she did not mention what she was using for a meter with her fingerstick because although a 20 point delta is considered in range by the CGM manufacturers, some additional difference could come from the meter used. What is usually more important is to figure out if the CGM most of the time reads higher or most of the time reads lower than the fingerstick. If there is equipment consistency, then the difference can be dealt with.


Cgm is great for showing bg trend, and does not directly measure bg in blood like a meter does.
If the trend is flat, it will better reflect your current meter bg.

Dexcom allows calibrations, that can help it get more accurate.
I don’t think Libre supports that.

Being hydrated can also lead to more accurate cgm readings.


I agree that Libre is not great for absolute numbers but for trends. Howeve, I find it gets more accurate after two or three days of wear.

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I use both. I always have a Dexcom because I can get it more accurate with calibrations. I wear a Libre because I can scan it when swimming.

The Libre is always off more. I relied on a Libre before a Dexcom and I used to automatically add about 20 points to it’s numbers. Now I can compare both and the Libre still usually trends about 20 points lower than my real BG level (on me.) The Dexcom I work at and calibrate it so it is only about 5 points off. The Libre does get a little more accurate towards the end of it’s 14 days.

For swimming it’s invaluable whether it’s off because it tells me my trending. I can tell if I’m staying stable or dropping. I carry gummy bears and gels with me snorkeling so I can keep swimming if I want to. The trending tells you a lot all on it’s own. But for me with dosing insulin you can’t beat a Dexcom. But both give you a lot more information than just finger sticking. I never had a clue I had DP until I originally put on my first CGM, a Libre. That 24 hour read gives you all sorts of information.

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i am so tired of fighting for decent medical care and equipment when I have medical insurance.

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@Christalyn Insurance companies rarely cover CGM’s for type 2’s. I think some might be starting to, but it might depend whether you are on insulin. But if you can afford it, a lot of people self fund Libre’s. You can download a free ap on your phone as a reader and each sensor costs around $37 and lasts 14 days. Costco in their membership program and Good RX seem to be the cheapest routes.

Even if you wear one or two, or off and on it will tell you a lot of information. You will still need a prescription.

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I have the Libre to check trends, but I don’t rely on it’s own reported values. Either it does not measure the glucose in the blood, but rather the glucose in the interstitial fluid, or because of user error.

Your experience is not unusual. I started using the Freestyle Libre in 2018. The first year it worked great. Though it was off by about ten points based on a lab test. Based on the Libre readings I should have had an A1C of 6.0, yet the lab showed an A1C of 7.1 (still not bad). The second year I had nothing but problems with the Libre sensors. I had about 7 of them give incorrect readings. I also noticed that Abbot reps had avoided offering a free sensor replacement and tried to stonewall when asked about a replacement. The Libre started to have way too many problems for my liking.

I keep hearing of similar problems with the Libre, and it’s rather disappointing. I’m glad I checked here before buying any. I might need a procedure soon, and it’d be nice to have a cgm during recovery, but it sounds like it might not help.

@Ray36 The Libre is off, anywhere from 10-30 points. A Dexcom is a better choice if you have that option. However having a CGM is better than not having one? It usually reads lower than you are at, but you know what you are trending…whether your numbers are dropping or rising or staying about the same. If you rely on finger sticking alone, you only get a snapshot of what your BG number is at that moment.

As long as you tell the Anesthesiologist to monitor and check your BG levels still. The CGM can let them know if you are dropping or going higher in between checks…

You raise very good points. Long ago, I had such poor management by anesthesiologists and PACU nurses that I had to be admitted to the endo ward within a few hours of waking. More recently, getting anyone to agree to test glucose levels, even with a letter from an endo, was a bust. When I was there for observation, they just wanted to test me before each meal, which was not working for me. If I’m 300 before a meal because they’ve put dextrose in my IV, then I’ll be even higher after eating 60 carbs of hospital chow. No clue why this was so hard for them to figure out. I just wanted at least an hour to drop before meals, but they acted like I was an alien for asking. I’ve heard they’re supposed to check every two hours, but I have never seen it. So, I guess any CGM is better than nothing, if possible.

I don’t know how I’m even going to get them to look at it. Has anyone had experience with that?

At least I’d have the history if they really muck it up, and maybe I could share data with someone as backup, right? Is that possible with this CGM?

(I’m just picturing my friend calling the main hospital telling them to check my dang blood sugar because I’ve been low for an hour, ha!)


The sharing of info while in surgery sounds like a good idea, I’m not sure how fast someone could try to contact the surgery team though so??? I don’t really know if an outside ap has Libre share capabilities, but Dexcom does.

A couple of threads that might interest you.

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Is this a super old post or is there someone still using an animas pump.

This is all about Libre, not animas!

(Some of the linked posts are very old, but not the direct posts on this topic).

@Timothy, The original post was from January. And then some scattered comments since then, the last one a day ago. The original date is at the top right and then the number of the post and the current date of the most recent post is to the right of each post.

Did anyone mention that Libre measures interstitial fluid not blood. Nancy50


Somehow, I missed this. Thank you for the links! This is very helpful.