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Dexcom g4 readings not matching bg

Layah2013

Well-Known Member
Messages
60
Type of diabetes
Type 1
Hi my daughter has been usi g dexcom for 3 days now and the readings on the dexcom are still not matching with her finger prick readings, i was told that for the first 24hr they would be out a little but there out by like 3 units for example she was 9.2 earlier and the dexcom was reading 12.7, ive did the 2 calibrations when first set it up and been doing the 12hr ones since then but its still out on the readings.. i only got this to alert me to her night time hypos but im worried now if the number are out by that much, as when i tested her finger yest tea time she was hypo at 3.2, but the dexcom was reading 5.1.. the dexcom didnt get down to a hypo reading untill after she was back up to 5.7 the dexcom was then saying she was 2.8 and alarming.. but id already found it befor the dexcom and treated it ... anyone get this with dexcom. Im mow back to testing her all night to check for the hyos as dont trust the dexcom now.

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Never used a Dexcom CGM, but if it works like the Freestyle Libre (which I'm sure it does) then you'll find a difference between measurements on your CGM and blood glucose meter.

There is a delay between the reading presented on the CGM to that of your BG meter due to them measuring different variables. Your BG meter measures blood obviously where as your Dexcom measures a quantity called interstitial fluid and then converts this data to an equivalent BGL value. There is a delay of 10-15 minutes between actual blood glucose readings and the interstitial fluid value. This would explain the situation with the hypo readings.

Try taking a finger prick test when you think your daughter's BGL is steady and then check the CGM for the half hour after and see if anywhere along that trend you get a similar value to the finger prick test.

Grant
 
The dexcom reading is 20 mins behind a finger prick test and if the reading is way out then calibrate the sensor again. If still causing problems then ring dexcom for a replacement.
 
Where is the sensor located? is your daughter hydrated? is it pressing on anything (trouser band/pump band? did you calibrate when bg was rising/falling?

Check out T1 CGM info on facebook if you can as well, lots of tips and tricks.
 
CarbsRok said:
The dexcom reading is 20 mins behind a finger prick test and if the reading is way out then calibrate the sensor again. If still causing problems then ring dexcom for a replacement.
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I have calibrated it again thankyou for that, i only wanted it to alert me in the night that she is dropping low so that i can treat her before she goes hypo, but im finding that im still needing to keep getting up testing her and shes already hypo and the dexcom hasnt picked that up, this is what her dsn said to get it for so i could finally get some sleep without worrying if shes hypo as the dxcom will alert me to this but as yet its not done that

Sent from my SM-A300FU using Diabetes.co.uk Forum mobile app
 

So what level have you set the alarm to alert you to a hypo?
 
Does she hypo at similar times each night?
 
Layah2013 said:
No there always different theres no pattern to them, shes in the lowest basal rate and it still happens thats why her dsn recomened dexcom but i just feel its been a waste of money

Sent from my SM-A300FU using Diabetes.co.uk Forum mobile app
Click to expand...

Understand you feel disheartened but as @CarbsRok said call up and get a replacement for your current one, as it appears to be too far out (needs to be 20% and this is 25isn out) have a couple of differnt times you have seen large differences ready for them.

Once that is done replace the sensor (wait for them to say they will replace it or give you further instructions) hopefully this is a one off.
 
Layah2013 said:
Its on 4.0 for hypo so i can get it before it goes below her dsn set it all up for her

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Well it's pretty dumb setting it at 4 isn't it? If you consider that there is a 20 min lag then surely it would be more realistic to set the alarm for 5?
You do seem to rely on your daughters dsn an awful lot, perhaps for both yours and your daughters sake you need to start sorting out her pump settings yourself and also the CGM. I make my comments due the pigs ear the dsn seems to be making of setting the basal and the CGM settings.
 
Bit harsh don't you think? People with queries aren't dumb, maybe just misinformed or lacking understanding.

If people didn't have queries then this forum wouldn't exist. Remember we're here to help, not belittle!

Grant
 
I have been using my Dexcom for just over a year now and have looked as deeply into this as a can - long story short - its not exact, its just a loose guide.

If you look at the literature Dexcom will tell you that CGMs (medtronic included) have about a 14% error reading from what BS actually are where finger pricks have closer to 4% (if you have a good meter) - so you will likely always see discrepancy between the two. This is due to the way the dexcom sensor checks the BS via interstitial fluid rather then blood directly - this method also will cause a delay anywhere from 10-20 minutes in readings, especially if they are rising or falling.

So if you have relatively flat sugars it will read fairly accurately, if they are rising and falling it will constantly it will lag behind and 'blunt' the peaks due to the rapid changes and slow response.

The best way to use a CGM is only a guide, it certainly cannot replace finger picks before meals, after exercise or when feeling strange, its mostly just piece of mind between finger picks or to catch unexplained changes.

Hope this helps, sorry to be a wet blanket lol I think having a CGM is better then no CGM, but i still finger pick 5-10 times a day most days because i know if it reads 5.1 it could really be anywhere from a 6.5 to a 4, depending on if its rising or falling,


EDIT - I set my low at 3.9, and high at 10 and turn off the 'rising' and 'falling' alarms. I just check frequently and act without the machine suggesting it to stay proper.
The alarms are good, but you will get 'alarm fatigue' fairly fast with a CGM unless you practice very good control. Alarm fatigue is basically just so many alarms so often that the severity of each one is gets lessened and lessened until you stop caring about alarms and miss a really important one - kinda like crying wolf lol
 
GrantGam1337 said:
Bit harsh don't you think? People with queries aren't dumb, maybe just misinformed or lacking understanding.

If people didn't have queries then this forum wouldn't exist. Remember we're here to help, not belittle!

Grant
Click to expand...

it was aimed at the nurse Grant not the OP
 

Using it to remote monitor a child and even given the descrepancy the vales shown are outside of allowable levels.
 
GrantGam1337 said:
Bit harsh don't you think? People with queries aren't dumb, maybe just misinformed or lacking understanding.

If people didn't have queries then this forum wouldn't exist. Remember we're here to help, not belittle!

Grant
Click to expand...
Yes thankyou for that that GrantGam1337. My daughter is 2 years old shes had diabetes for only 4 months which she was on prn therapy first while waiting to gk on pump therapy, which she has been on for 4 weeks, and has suffered night time hypos since then her basal rates are at the lowest they can go i cant do anything else about that, and how the hell am i supposed to know what to do next with out the help of her dsn im mo expert in diabetes in children thats what her dsn is there for im still learning things, i came on here for advise no to be spoken to like that, i am scared to sleep at night incase my daughter doesnt wake up from a hypo so im checkin her every 2 hours, i didnt no what else i could do so yes i asked her dsn for help which is what they do.. she suggested the dexcom so i could get some sleep without worrying of shes going to wake up.. it does not say any were in the dexcom hand book that there is a 20 min delay or i wouldnt be on here askin if anyone else has had this with dexcom. Why should i be made to feel an idiot for wanting to keep my daughter safe, i dont no anyone else that has diabetes i didnt even no what is was myself untill she got it sk forgive me for askin for advice

Sent from my SM-A300FU using Diabetes.co.uk Forum mobile app
 
Ok thankyou for that, i had no idea about dexcom untill her dsn said this will help with alarming me to night time hypos so i can get some sleep without worrying shes not going to wake up from a hypo as she doesnt wake up herself when she has one in night she shows no symptoms,

Sent from my SM-A300FU using Diabetes.co.uk Forum mobile app
 
GrantGam1337 said:
Bit harsh don't you think? People with queries aren't dumb, maybe just misinformed or lacking understanding.

If people didn't have queries then this forum wouldn't exist. Remember we're here to help, not belittle!

Grant
Click to expand...
The dumb I can assure you was not referring to Layah it was in reference to the dsn who set the CGM and pump up in the first place.
 

No problem!

Reading your last post and now knowing that she is 2 and recently diagnosed you may be witnessing what is actually going on during the 'honeymoon' period. She likely still has some insulin being produced but in sporadic bursts at strange times. This would cause a lot of flux in her sugars and would probably result in very 'random' looking readings on a CGM due to the lag and frequency of change she is probably experiencing.

I would stick with it, and just fight through the 'random' times. Use it as your doc suggests, and do your best. Over time the honeymoon period should fade and things will become more linear and predictable. You're in a strange time right now with her diabetes.

As for symptoms - she is really young, and the symptoms of a low can be fairly subtle, she may just not know how to describe it yet. As adult the best I can do is 'I feel off' lol until they are into the low 3s then i just feel slightly faint, and have a mild tension headache at the top of my head... I would imagine this would be hard on a 2 year old to notice and describe.

Best of luck - things will get better!
 
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