Sensor Readings All Over The Place!

[Neckarski_94]

Readings all over the place! Calibrated it as there was a difference of 20+. Meter was saying 11.8 and CGM 14. Dropped to 12.4 then back again! What do I do now??

 

[grantg]

If choosing to calibrate it's best done at stable readings where the graph has no sudden movements and is flat as possible. Cgm also runs behind blood glucose approx 15 mins lag.

Another thing you should take into consideration is finger prick can be out. It may read higher or lower depending on which use will be difference. Same goes for cgm which are generally a little less accurate than finger prick levels

Now imagine cgm being out on the lower side with finger prick being out on the higher side.. the difference between the two can be higher than expected.

Finger-Stick Glucose Monitoring: Issues of accuracy and specificity - PMC

pmc.ncbi.nlm.nih.gov

What is MARD?

Another evaluation method used in clinical studies to represent device accuracy data. The MARD (Mean Absolute Relative Difference) measures the average difference between a device measurement (or test result) and the reference measurement at normal to high glucose levels. The lower the MARD, the...

www.freestyle.abbott

Various Meters/monitors have their own error margins. So your reading appears 'accurate enough' given the approx 15min lag

 

[Antje77]

Calibrated it as there was a difference of 20+. Meter was saying 11.8 and CGM 14.

I don't understand.
That's only a difference of about 2 mmol/l, and both numbers were saying you were slightly out of range but not dangerously so.

Graph shows you were on the highish side but not extremely high most of the day, ignoring that first high which you caught very nicely.

What do I do now??

We can't tell you.
Right now you're at somewhere between 12 and 14, which is basically the same number, a little high but not alarmingly so.
More importantly, you have been quite stable for hours, no big drops or rises.

But we have no idea when you last took insulin, do you have any IOB (insulin on board)?
We also do not know what you have eaten in the last 4 hours.

Those are the things you want to look at if you want to decide on what you want to do now.

 

[Neckarski_94]

If choosing to calibrate it's best done at stable readings where the graph has no sudden movements and is flat as possible. Cgm also runs behind blood glucose approx 15 mins lag.

I was stable when I took the reading.

 

[Neckarski_94]

That's only a difference of about 2 mmol/l, and both numbers were saying you were slightly out of range but not dangerously so.

How is 11.8 and 14.0 2 mmol/l difference? To me that’s not accurate at all. My readings don’t seem to be droppping on CGM!

 

[Antje77]

How is 11.8 and 14.0 2 mmol/l difference? To me that’s not accurate at all. My readings don’t seem to be droppping on CGM!

It's a 2.2 mmol/l difference, which is not a large difference, both say you're in the low teens.

If your readings aren't dropping, you'll need to think about when you last took fast acting insulin and if this still may be active before deciding on a correction dose.

 

[Neckarski_94]

It's a 2.2 mmol/l difference, which is not a large difference, both say you're in the low teens.

I can’t see were you are getting 2.2mmol/l difference from 11.8 to 14 is not 2.2 it’s a 20.2 difference!

Just checked again with a finger prick 11.2 and CGM was 12.2 a little closer than the last time I checked. I hate inaccuracy!

 

[lovinglife]

@Antje77 is correct in their maths

I think you are forgetting to put your point in or putting it in the wrong place, not sure how you’re calculating to be honest

Try it on a calculator 14.00 - 11.80 =2.2

You calculated right with the
12.2 - 11.2 =1
This isn’t inaccurate

Use the same sum for the 14.00 & 11.80 reading

 

[EllieM]

Remind me if you've been on a DAFNE course yet and/or been taught to do correction dose?. As the others have said it's not a big difference, if you take the mid point of 12.9 then both meter and cgm are less than 10% out....

What you do depends very much on how recently you last had insulin and when you next plan to eat/inject....(And what your various insulin ratios are.)

If it's any consolation I've been struggling to get down from 15 for half of the day. (Playing bridge and I assume that stress just means I need much more insulin....). I'm now back to normal and will just remember to take extra next time....

 

[Neckarski_94]

is correct in their maths

I have never been good at maths!

Try it on a calculator 14.00 - 11.80 =2.2

That calculation is correct

You calculated right with the
12.2 - 11.2 =1
This isn’t inaccurate

You see to me that is a difference of 10 not 1. Which is a lot closer than a difference of 20.2!

 

[Neckarski_94]

Remind me if you've been on a DAFNE course yet and/or been taught to do correction dose?. As the others have said it's not a big difference, if you take the mid point of 12.9 then both meter and cgm are less than 10% out....

Been on DAFNE. Didn’t understand any of it. So I’m not doing correction doses. What was there to correct anyway? CGM was at 14.0 and fingerprick was 11.8 so no need for correction in my opinion.

It’s just all too much for my brain to function all of this!!!

 

[grantg]

Been on DAFNE. Didn’t understand any of it. So I’m not doing correction doses. What was there to correct anyway? CGM was at 14.0 and fingerprick was 11.8 so no need for correction in my opinion.

It’s just all too much for my brain to function all of this!!!

theres a couple of apps available which you maybe could find useful, mySugr alongside myLife. in those apps youcan set your insulin to carb ratio. you would enter the amount of carbs planning to eat and it would then give you the doseage of insulin.

carbs & cals app is another application which has a visual aid to assist with carb counting would be rough guide.
there are also appplication ssuch as GlucoSense which where you upload an image of your food giving a small description which uses ai to help guess the carb content. SNAQ is another one, theres a few others that have been mentioned on the forum in other threads coulds be of use to you to help reduce the maths.

 

[EllieM]

Been on DAFNE. Didn’t understand any of it.

I have never been good at maths!

Have you spoken to your diabetic team about your difficulties with mathematics? It might make it easier for them to help you, because most explanations of carb counting and insulin dosing assume that people can learn it via a maths explanation...

 

[jaywak]

From my experience of type 1 I would say your graph is not that bad , some days are perfect but not many , and some days can be bad , I would stop beating yourself up stress can effect your bgs you know .

 

[Introverted_And_Proud]

Readings all over the place! Calibrated it as there was a difference of 20+. Meter was saying 11.8 and CGM 14. Dropped to 12.4 then back again! What do I do now??View attachment 73314

Hi there, Neckarski.

I'm not sure how familiar you are with the CGMs at this point. But as others in this thread have pointed out, it's normal for there to be a bit of a variation between CGM readings and finger prick readings. The most common reasons for this usually boil down to the following: CGM readings come from the interstitial fluid (ISF) in the body while finger prick readings are taken from the blood, the latter of which is concerned more accurate for glucose readings; your blood sugars are rapidly moving up or down following meals; CGMs usually lag behind finger prick readings by a little bit, so there's a slight delay before they inevitably 'catch up'; following activation of the CGM sensor, it can take up to 48 hours before readings properly stabilise and read similarly to the meter, due to it needing to get used to your body.

As a general rule of thumb, it's accepted that the sensors and the meters are very unlikely to match exactly with their numbers. But if there are any sensor readings you're unsure about, especially if the sensors don't match how you're feeling, it's usually advised to always check with your meter, which you're already doing. While meters aren't 100% accurate either, their readings are considered to be more accurate than the CGMs. The only time you should be concerned about the sensor readings variance is if it's continually way out of your finger prick, as this can indicate your sensor might be faulty. But looking at the example and figures you've provided, I don't think that's the case at the moment.

If you're struggling with correction doses and other calculations related to your diabetes management, as others here have said, it's best to consult with your diabetes team or doctor. They can give you suggestions for diabetic apps that can help you calculate your doses or carbs and even walk you through the setup for all the calculations. @grantg has provided some good suggestions in their post for apps, some of which I use myself and have found very handy.