First A1c on Libre (instead of Dexcom)

I just got my first A1c after three months of Libre use. It rose from 6.5% to 7.1%.

I was working hard to get that 6.5%, and I’m still working just as hard. I think this is a reflection of a) no alarms (although I do scan 20+ times a day, but no alarms really has an impact at night) and b) the Libre often reads 2 mmol/L lower than my actual blood sugar. So I can think I’ve cruised along in my upper range for hours when, in reality, I’ve been high for hours.

Time to work harder, wear the MiaoMiao more, and test more often…


I really think nights are the biggest problem with having no alarms. My A1C has risen a bit too since I stopped using Dexcom, though to be honest I was best with the G4 - those receiver vibrations were scary loud! I couldn’t really hear the G5 on my phone a lot of the time and would sleep through highs. The only thing I can suggest is that I’ve found when I eat dinner earlier and avoid desserts or snacking after dinner of any kind, my overnights are very predictable. This has made a tremendous difference, but now that I’ve said this they will probably go haywire again!


First - Congrats on two very respectable A1c’s. Sorry the Libre isn’t working as well for you, hopefully every CGM will have the ability to alert you soon.

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The overnight thing is a tough one. I have a MiaoMiao, but it seems really finicky in that sometimes it alarms every five minutes and yet if I try to snooze it then it doesn’t alarm at all, and sometimes seems to disconnect completely until I open the app. Also, since I haven’t been having alarms at all hours of the night, my sleep has been SO good. I sleep like a baby. Got o sleep and don’t wake up until morning. I’m not sure I’d want to give that up…

I think a bigger part of the problem is this:

That 4.1 mmol/L is a number I’d typically treat as an “oncoming low” but clearly I am right in my target range. Another time today I tested when the Libre showed 3.4 mmol/L and my meter showed 5.1 mmol/L. So if I’ve been treating a bunch of false lows, it would make sense that I’d be spending more time high (with the Libre not necessarily showing it for minor highs) and push my A1c up higher.

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I had a similar issue and found out it was the aleve I took and lasted for about 8-10 hours…the libre tends to give you false lows to “fix” the false highs acetaminophen usually gives…they advertise no contraindications, however, the only thing they did was alter the algorithm… the problem is its on the libre and will also affect xdrip readings… I think any other med might affect your readings also…especially any nsaid’s

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Aleve is naproxen, not acetaminophen, and shouldn’t have any effect on your CGM, unless the Libre is entirely different from the Dexcom in that respect.

It is very different… I think all nsaids will affect the libre which is why I brought it up…ibuprofen, etc will also affect it…abbott still claims no contraindications though

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Is that just when you’re sleeping/lying down, or is it constantly showing you lower than you are? I definitely find it reads lower overnight, but Dexcom was the same for me.

I’ve never noticed any problem with the Libre and acetaminophen, I forgot that was even an issue with CGMs.

Acetaminophen is fine… all the other nsaids are a possible issue…I was just warning people because I had a few days where the libre was always 50-70 mg/DL lower than my glucometer, and I remembered I took naproxen sodium (aleve)…stopped taking it and the libre was accurate again…

Have you had a chance to reproduce and/or test this. The reason I ask is that things adding current like acetaminophen makes sense from an operational sense, but having worked in the area for 5 years, I never ran into anything that suppressed the current from the sensor, and so I am genuinely curious.

Once I discovered the problem, I tried ibuprofen instead of naproxen sodium, and the problem still existed. I think abbott focused on fixing the acetaminophen problem, and succeeded with acetaminophen… but the solution caused unforseen problems with other nsaids and perhaps other meds also…I almost ripped off the sensor and was going to call them, but remembered the naproxen sodium…

I don’t take pain medication very often, so am not actually sure how much of an impact it has on the Libre or Dexcom. The few times I’ve taken Advil over the past few years, I don’t think I’ve noticed any effect.

My Libre seems to be anywhere from 0.5 to 2.0 mmol/L off. It doesn’t really seem consistent except that the first 24 hours is definitely worse. I’ve been testing more often and it’s definitely always lower than my meter, although in the past I’ve seen it be higher as well occasionally, usually with high-highs.

I’ve upped my basal rates by 0.2 units an hour because, in general, I’ve just been running high lately. I think the combination of testing and trying to get my average blood sugar down a bit (currently 8.3 mmol/L according to the Libre) will reduce my A1c next time.

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Have you considered connecting it to nightscout (my understanding is that the miaomiao can be connected to nightscout)? Once you connect to nightscout, you can then connect to sugarmate. I understand it’s a 2 step process, and some may consider that a hassle, but the alarms in sugarmate are the most customizable I have found. The highly customizable nature would seem an effective way to address the 2 mmol error you routinely experience with the libre.

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I used to have this exact problem where the Libre reader would indicate false lows. What app are you using for the MiaoMiao? I use XDrip and I find it to be significantly more accurate than the Libre reader because it accepts calibrations. If you don’t want to have the MiaoMiao attached all the time, you could just scan with your phone. That way the scanned values will be just as accurate as the ones received over Bluetooth.


I use xDrip on my iPhone, but it’s not anywhere near the sophistication of the xDrip+ app on Android. And I think it’s a large part of what’s so finicky and frustrating about using the MiaoMiao. I have an older iPhone, so no ability to scan with my phone until I upgrade. One concern I’d have with xDrip (on iPhone, no online connection( is how to get my readings in a format my doctor can look at. Since the in-range charts generated by my Libre will be useless. I’m aware of Spike, but just need to find the time to look into how to set all that up, since it’s pretty complicated.

Last night I woke up at 2.8, where it showed me flatlined all night. When I tested I was 4.0, which is an okay reading for me. This morning Libre showed 5.0, meter showed 6.4. And yet twice yesterday I tested and the result was dead on with the Libre, once at 6.5 and once at 14.5. So I’m not sure how to tell when it’s off versus not. The off readings definitely aren’t just at night, as demonstrated by the photos in the above posts that were taken at mid-morning.

Yeah, I’ve heard about some version of XDrip on iPhone, but never seen it. If you decide to upgrade at some point, then maybe an Android phone would be an option? Spike might be able to do something similar with the NFC scanning, but I haven’t used it so can’t really say. For a graphical presentation, I think a Nightscout site would help. It can generate all the typical charts.

How is the accuracy in XDrip when you have the MiaoMiao on?

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Hi Jen, I have a question for you. You had mentioned that you have a difference between BG and sensor readings. Did you remember that there is a 15 minute time delay in these results? i.e. The reading from you sensor will show you what you BG was 15 minutes ago and the blood test will show you your BG now.

To compare properly, do the good old finger stick. Wait 15 minutes and then scan the sensor. Compare those results and you should have a more accurate comparison.

I never had the opportunity to use the DexCom, and I’m new to the Freestyle. Since the Freestyle Libre 14 day is my first CGM, I’ve memorized all the specs so that I could better understand the differences between the blood test and scanning.

Good luck and I hope you can find a solution.

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Are you sure about all that? The “MARD” figure of merit for CGM is the difference between what a CGM says the BG is right now and what a laboratory meter says the BG is right now. The CGM algorithm uses the history of past readings plus its estimate of lag to predict (extrapolate to) the current BG. They’re not trying to show a number that your BG will reach in 15 minutes. Their predictions are generally pretty good; that’s why the FDA says it’s generally safe to dose insulin based on the CGM reading alone. There are known exceptions, such as when a sensor is new, or when there’s a pressure low from sleeping on the sensor, or when the BG trend is changing fast (like shortly after eating glucose to correct a falling BG.) In those circumstances the glucometer is our friend.

And I wonder if your “15 minute lag” figure is up to date. The studies on the G6 showed an average lag of about 5 or 6 minutes, and it would be surprising if the Libre was 3 times slower.

I think the 15 minute lag was true for the G5 in our experience. The G6 is better with lag, but still the sensor predictions are wrong for us when blood sugar is changing rapidly. With that being said, I think MichaelS’s comment that lag should be taken into account is valid, however as you point out the specifics of the lag may not be correct. I don’t think I have seen a sensor lag study with the Libre.