CGM accuracy- any tips?

[lilyfleur]

Hello everyone, I've been given CGM just for 6 days to try and work out why my blood glucose is fluctuating so much for no apparent reason. It's been on for nearly 24 hours, and so far has been completely inaccurate! The CLOSEST it's been to my meter readings is 6mmols, so I'm thinking it's a waste of time unless I can work out how to fix the problem.
I've calibrated when my sugars have been stable (and good) but the pump doesn't alter the results based on what my meter says so what's the point in calibrating at all? It's made absolutely no difference to the accuracy

Any ideas?


Type One Diabetes since 2001, Coeliac Disease since 2003 ish, IBS, and on and off depression and diabulimia.

Current HbA1c 11.7%

 

[AlexMBrennan]

It would help to know which CGM you were given, and when in doubt I think it would be better to give your DSN a quick call rather than waste a week's CGM time.

but the pump doesn't alter the results based on what my meter says so what's the point in calibrating at all?

I think you completely missed what calibration means in this context: What we are mainly interested in are blood glucose levels, which we usually measure by pricking fingers and taking a capillary blood sample. CGMs work differently and measure sugar levels in interstitial fluid instead - by "calibrating" how the actual blood glucose relates to interstitial fluid measurements, allowing it to estimate BG levels.

This process can take up to a day (considerably longer if you screw up callibration tests - having BG change too much near calibration tests renders the result useless). If the problem persists for another day, I would definitely suggest you contact your DSN/consultant.

It is possible to connect insulin pumps to CGMs, but I don't think it would really help if you only have the CGM for a week.

 

[lilyfleur]

I'm already on an insulin pump so it is connected to it, and it's the Medtronic Paradigm Veo with enlite sensors. If it normally takes a day or so I guess I'll just have to wait and see if it improves. I'll try calling my DSN but there's very little chance of getting hold of her! That's why I thought I'd ask on here and I wouldn't waste the time on it by not using it anymore or anything, I just meant that I'd be annoyed if I got to the end of the week and the results were useless because they weren't even remotely accurate. Hopefully if it doesn't improve medtronic might be able to help somehow if I can't get hold of my nurse.

Thanks for the advice


Type One Diabetes since 2001, Coeliac Disease since 2003 ish, IBS, and on and off depression and diabulimia.

Current HbA1c 11.7%

 

[Flowerpot]

Hi Lilyfleur

I use Enlite sensors and often find approximately the first 6 hours give me a bigger difference between interstitial glucose levels and blood glucose. It then usually settles down and is pretty accurate after that increasingly so the longer the sensor has been working.

If the difference in glucose meter and CGM readings are vastly different you will get a calibration error message after which the sensor warms up again for a short period. I haven't had many of those but usually it resets at a more accurate level. If the accuracy doesn't improve and you can't contact your DSN I would give Medtronic a ring as they have helped me out with sensor problems before. I hope you get better accuracy from it soon.

 

[Spiker]

I've never seen a Dexcom G4 sensor be out by 6 mmol/L even right out of the box. 2 maybe, in extreme cases 3, but not 6. The calibration is pretty smooth and seems to get progressively better over the first 24 hours and then continue improving for the first few days. In the first 6 hours I would definitely be taking the reading with a pinch of salt, but

BIG BUT

You are never supposed to make any treatment decisions on a CGM reading. Always use a fingerstick reading to calculate any insulin dose. This is important!

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