Anyone else get wildly inaccurate Dexcom readings?

Garak

Active Member
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29
Type of diabetes
Type 3c
Treatment type
Insulin
Hi all,

I’ve been using Dexcom One sensors for a few months now. My readings are mostly 30-50% out compared with blood glucose readings. However, I’ve read they’re meant to be within 15% of a finger prick result. I’ve tried locating them on the back of my arms and on the sides of my abdomen, but nowhere seems to give reliable readings, not even in the middle of the sensor period. There seems to be little point in the NHS funding these in my opinion, or is this just me? Interested in knowing what other people’s experiences with these are? Thanks
 

In Response

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3,626
Type of diabetes
Type 1
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What are your levels like @Garek ?
I ask because CGMs seem to be designed to be most accurate at “normal” levels and anyone with higher (or lower) levels will see more inaccuracy.
 
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Garak

Active Member
Messages
29
Type of diabetes
Type 3c
Treatment type
Insulin
What are your levels like @Garek ?
I ask because CGMs seem to be designed to be most accurate at “normal” levels and anyone with higher (or lower) levels will see more inaccuracy.

Depending on date range, Dexcom says my ‘time in range’ is between 65 and 90%. Though if my BG reading is say 5.6 then quite often Dexcom will say I’m in the low 3’s so TIR isn’t that accurate. I have to set my low alarm to the absolute lowest otherwise it’s constantly going off.
 

MattInUSA

Active Member
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40
Type of diabetes
Other
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I do not have diabetes
I have to set my low alarm to the absolute lowest otherwise it’s constantly going off.
I don't use a CGM, but my supervisor's husband does. One of their complaints has been that it alarms in the middle of the night due to him being dangerously low, yet he feels fine and the finger sticks concur with him. I don't know if they're generally inaccurate, or if some people are more prone to inaccuracy, but you're not alone.
 
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Garak

Active Member
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29
Type of diabetes
Type 3c
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Insulin
I’ve had my latest sensor on about 3 days. So far it’s surprisingly accurate (within 2 mmol). This time I positioned it just below my rib cage. Hopefully this will continue to be a good location for me. Thanks for your comments guys.
 

IanA123

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53
Type of diabetes
Type 1
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Insulin
Freestyle libre is hopeless, alerted me to being low and a scan showed 3.3, finger prick showed 12.4. Repeated finger prick and got same result 5mins later. Freestyle showed 2.9. Consultant did state finger prick is gospel amd they are aware of the inaccuracies of the cgm devices.
 
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Garak

Active Member
Messages
29
Type of diabetes
Type 3c
Treatment type
Insulin
Freestyle libre is hopeless, alerted me to being low and a scan showed 3.3, finger prick showed 12.4. Repeated finger prick and got same result 5mins later. Freestyle showed 2.9. Consultant did state finger prick is gospel amd they are aware of the inaccuracies of the cgm devices.

I’ve tried the Libre 2 quite a few times previously. They were inaccurate for me, but consistently inaccurate. Always 2-3mmol lower when my BG was low, and 2-3mmol high when BG is high. With the Libre 2 I always wore them on the backs of my arm. My current Dexcom 1 is much better located just beneath my rib cage, strangely when it first went on, but has become less accurate as the days pass. Still, better than when I tried them on the backs of my arms and the lower sides of abdomen. Perhaps try yours in some different places if you haven’t already. I’d probably be happier if they would move me on to the Libre 2, but I can’t afford to buy them, and my DN tells me there’s no chance of me getting them. We’ll see what my endocrinologist says when I finally get an appointment . Thanks and good luck, I hope you find something more reliable.
 

Nageshrao

Newbie
Messages
2
Type of diabetes
Type 2
Treatment type
Tablets (oral)
I have been using Dexcom One for about a month and so far it has been disappointing. Once the app stopped working completely and then I deleted the app and reinstalled it followed by a new sensor, which started giving me low readings overall and a very low alert at the least four times in one night!!! I had to remove it and replace it with yet another. This time I contacted Dexcom technical department and today, I got a free replacement sensor. Obviously, their sensor problem is not new. Only time, the Dexcom readings are somewhat close to BG reading is when the arrow is straight ahead [i.e stable]. If it is rising or dropping, there is absolutely no correlation. I am beginning to think it is a waste of money.
 
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IanA123

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Messages
53
Type of diabetes
Type 1
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Insulin
I’ve tried the Libre 2 quite a few times previously. They were inaccurate for me, but consistently inaccurate. Always 2-3mmol lower when my BG was low, and 2-3mmol high when BG is high. With the Libre 2 I always wore them on the backs of my arm. My current Dexcom 1 is much better located just beneath my rib cage, strangely when it first went on, but has become less accurate as the days pass. Still, better than when I tried them on the backs of my arms and the lower sides of abdomen. Perhaps try yours in some different places if you haven’t already. I’d probably be happier if they would move me on to the Libre 2, but I can’t afford to buy them, and my DN tells me there’s no chance of me getting them. We’ll see what my endocrinologist says when I finally get an appointment . Thanks and good luck, I hope you find something more reliable.
Have tried in different places to no avail. Endocrinologist doesn't seem concerned, just moronic GP that has an issue because they can't see the readings and I refuse to show them. They have not had appropriate training or specialism so my diabetic care is through the hospital, patient choice. Though the fact my insulin was changed to tresiba and apidra and I have zero hypo awareness on these and even reporting to the clinic, they are dismissive and unhelpful. Hopefully, I will get a referral and 2nd opinion from another trust soon.
 
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Garak

Active Member
Messages
29
Type of diabetes
Type 3c
Treatment type
Insulin
I have been using Dexcom One for about a month and so far it has been disappointing. Once the app stopped working completely and then I deleted the app and reinstalled it followed by a new sensor, which started giving me low readings overall and a very low alert at the least four times in one night!!! I had to remove it and replace it with yet another. This time I contacted Dexcom technical department and today, I got a free replacement sensor. Obviously, their sensor problem is not new. Only time, the Dexcom readings are somewhat close to BG reading is when the arrow is straight ahead [i.e stable]. If it is rising or dropping, there is absolutely no correlation. I am beginning to think it is a waste of money.

Yeah, I feel your frustration. I had to totally disconnect the Dexcom app from a Apple health to get it to be stable. If you’re using an iPhone I would recommend trying that. I can only imagine how much money the NHS is wasting on these. For me, Dexcom support was pathetic, they haven’t even replied to me. Perhaps they don’t want to keep replacing their faulty sensors.
 

Jimphillips

Newbie
Messages
3
I use Freestyle Libre 3 and to be honest it’s very accurate - although being c15 min behind blood sugar readings because of measuring interstitial glucose …. So stable glucose level is most accurate and going up it’s behind the curve likewise going down - this you have to compensate for yourself
 

Jimphillips

Newbie
Messages
3
I use Freestyle Libre 3 and to be honest it’s very accurate - although being c15 min behind blood sugar readings because of measuring interstitial glucose …. So stable glucose level is most accurate and going up it’s behind the curve likewise going down - this you have to compensate for yourself
A few failed after 6-7 days I think was a batch problem but Abbott replaced all for free and fast !
 
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Garak

Active Member
Messages
29
Type of diabetes
Type 3c
Treatment type
Insulin
Have tried in different places to no avail. Endocrinologist doesn't seem concerned, just moronic GP that has an issue because they can't see the readings and I refuse to show them. They have not had appropriate training or specialism so my diabetic care is through the hospital, patient choice. Though the fact my insulin was changed to tresiba and apidra and I have zero hypo awareness on these and even reporting to the clinic, they are dismissive and unhelpful. Hopefully, I will get a referral and 2nd opinion from another trust soon.

Yep, I can definitely relate. I was begging my DN to let me have insulin for at least a year. Her response was I’d get fat on insulin, just stay on Metformin. She refused to accept the existence of type 3c. Metformin never did anything for me. It took my pancreas to completely fail before she let me have insulin. Now I have a diagnosis of Autonomic Neuropathy and they seem to let me have anything I want. A bit late though! I now have hardly any hypo awareness, not until I hit about 2mmol at least. It’s pretty **** eh? Good luck to you
 

Garak

Active Member
Messages
29
Type of diabetes
Type 3c
Treatment type
Insulin
A few failed after 6-7 days I think was a batch problem but Abbott replaced all for free and fast !

They sound good, but I’m guessing you’re in the US? I don’t think you can get them in the UK yet.
 

IanA123

Well-Known Member
Messages
53
Type of diabetes
Type 1
Treatment type
Insulin
Yep, I can definitely relate. I was begging my DN to let me have insulin for at least a year. Her response was I’d get fat on insulin, just stay on Metformin. She refused to accept the existence of type 3c. Metformin never did anything for me. It took my pancreas to completely fail before she let me have insulin. Now I have a diagnosis of Autonomic Neuropathy and they seem to let me have anything I want. A bit late though! I now have hardly any hypo awareness, not until I hit about 2mmol at least. It’s pretty **** eh? Good luck to you
I had hypo awareness on insulatard and humilin s, but yet again fell for the lies of analog insulins. Was told, oh you will be taking a lot less insulin than you are on now, yet here I am 3months later on double the insulin dose.
 
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Garak

Active Member
Messages
29
Type of diabetes
Type 3c
Treatment type
Insulin
Interesting, I’m on insulatard, but it only seems to last 13hrs, so I get highs overnight. I have a few Humulin I pens left over that were 2x a day. I think going back to these might be a better fit for me. Because I have gastric paresis novo rapid isn’t lasting long enough at night. Most of the day I drink Huel which allows me good control with Insulatard and Novorapid combined, but it’s at night when I eat a meal that’s the problem. Life just seems rubbish if you can’t enjoy a meal, and at night works best for me as I’m sleeping when solid food makes me feel rubbish, so I don’t notice it as much. If I overdo it with a takeaway for example, I really suffer in the morning though .
 
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TigerTailz

Member
Messages
9
Type of diabetes
Type 3c
Treatment type
Pump
HI Garek,
I'm a Dexcom user, switched over from Libre 2, as I now use an insulin pump as well. I have found that you need to calibrate the Dexcom with approx 4 finger pricks over the first day of wearing a new Dexcom device. If you also have a pump, I have found that when you change the cartridge it often - not always - needs to be recalibrated again with a couple of finger pricks.
Libre 2 normally only needed 2 finger prick calibration at the start of wearing a new Libre device. My friend in the US uses a Libre 3, which doesn't need calibration at all.
Hope this helps!
 
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Garak

Active Member
Messages
29
Type of diabetes
Type 3c
Treatment type
Insulin
HI Garek,
I'm a Dexcom user, switched over from Libre 2, as I now use an insulin pump as well. I have found that you need to calibrate the Dexcom with approx 4 finger pricks over the first day of wearing a new Dexcom device. If you also have a pump, I have found that when you change the cartridge it often - not always - needs to be recalibrated again with a couple of finger pricks.
Libre 2 normally only needed 2 finger prick calibration at the start of wearing a new Libre device. My friend in the US uses a Libre 3, which doesn't need calibration at all.
Hope this helps!

I don’t think there’s a way to calibrate the Dexcom One. Let me know if I’m mistaken as that would be good. Thanks
 

TigerTailz

Member
Messages
9
Type of diabetes
Type 3c
Treatment type
Pump
I don’t think there’s a way to calibrate the Dexcom One. Let me know if I’m mistaken as that would be good. Thanks
I'm using a Dexcom G6, and with this one you calibrate it in the app, just go to 'settings' then 'calibrate' and type in the finger prick reading. I've never used a Dexcom One, but if it has an app then I would have a nosey in there first. If not, maybe you could you try calling your Diabetes Team and asking them? Best of luck.
 
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iwhoadmin

Member
Messages
22
I have been using the Dexcom for about 4 years and find it very inaccurate in the last 2. I have had to change sensors often, sometimes within 1 or 2 days of putting it in. Now I am finding that at any given point it just loses the signal or reports the sensor is not responding and for no discernible reason. And this is very troubling for me as I have been thinking of going on an insulin pump that uses readings from the Dexcom.
 
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