Sensor Error on Minimed CGM?

Hi, I’m having a sensor error on the MM sensor my daughter is wearing. I had the same issue earlier today and was on the phone for a long time with a MM person trying to troubleshoot. i ended up having to take the sensor out and do another this evening. Before it was time to have the 2 hour calibration after soaking, I got this sensor error and it continues to beep. It’s almost time to do the 2 hour calibration and I am on the phone waiting for someone at MM to be available.

I know that the site is good, good contact, inserted fully into her skin, nothing on the skin, etc...We've done about 4-5 other sensors in the past 2 weeks and had no troubles. In fact, it's been amazingly easy, pretty accurate numbers, able to change her basals, target numbers, etc. with the Endo which has meant more time in the target range.

Anyone have this problem? Any ideas on how to fix it or what might be the trouble?

Thanks in advance~

Hi, John,

Thanks for your response. I just got off the phone with Medtronic and he said the same thing about the Isig which had been 0 or below 2. then we tested the transmitter with the test plug and the trasmitter was working. He had me restart an old sensor on the sensor screen and now I have to wait another 2 hours to calibrate and then the next 4 hours to calibrate again. her Isig seems to be higher this time around, so I’m hoping it just needed to soak more.

I like your suggestion about letting it soak 6-10 hours. I will try it and hope that helps.

thanks so much! I appreciate it!

I’m on the MM cgms too with transmitter.
I have no idea what the Isig is and how to control/influence it. Please JohnG could you write a brief description of it, if not too much trouble? My current Isig is 14.68.


Click here to read an older discussion when I asked about this. I got some very helpful answers!

Hi Kristin - I too am on mmol/l so just wanted to check - did you calculation work re the Isig levels and current BG? So I’ll only calibrate if the sum is like u said - between 0.08 and 1.1. And this should give me better accuracy?


PS sorry for postin a reply here Kristin, but I was having trouble posting on the original post. Thanks!

Yes Mark, I followed that rule and it seemed to work. I was only on a trial with the sensor for one week.

MM admits that the “Meter Now” should not be followed until the isig is within range as described. Give them a call and have them walk through how to determine when the isig is within range. This advice from MM was the best I have received from them with the cgm.

The reset described by others here works, although I have found that the turn off time to clear the error is only about an hour for me.

Over calibration or trying to calibrate when BGs are rising or falling will cause confusion for the software and result in out there BGs or errors.

When you let the sensor soak for 6-10 hours do you have the transmitter attached?

Some of my “best” sensors have been ones that gave me trouble at the onset. I just clear the sensor error and keep the sensor in for a few hours and then try again. Most of the times this is successful and the sensor goes on to be a good one. Other times I’ll get the same error again at which point I’ll insert a new one. So I agree the wetter the better!

Hi, All~
After I restarted the sensor, it seemed like the Isig # was increasing and I was hoping it would work. Around 2am the pump said to enter BG, and I did, but then it beeped and said it wasn’t correct. I knew her BG was pretty stable since she wasn’t eating or having a bolus at that time, so I cleared it out and kept waiting (while I slept! :)) to see if soaking it further would correct the problem. At some point in the night it rejected the BG # I entered and said it was a bad sensor. So…when we woke up, I just took it out and went the day without the sensor. Frankly, it’s frustrating and after having all of that information for about 10 days, I felt like I was walking in the semi-dark again, trying to dose Elisabeth for her food, etc without those wonderful little arrows. I LOVED not having to check her BG all the time, and the changes made in her insulin basals, etc. due to the CGM data have really made a difference in her BGs this week.

Mark, the first week the CGM trainer accidentally took my sen-serter with her, so I actually did leave the sensor in for 6 days at her recommendation, but I have been changing them out at 3 days since then. She’s only 4 years old, so I wanted to see how it would affect her skin before trying to get too many days out of it.

Thanks everyone for all of your help. I plan to try again tomorrow when I can speak to the trainer again.

If you BG is not flat (it is going up or going down) and you enter a BG when asked it will NOT calibrate accurately. The outcome you describe is typical of trying to calibrate when the BG is not stable.

You can always restart it. I have restarted my sensor up to 4 time during a six day use. And it performed surprisingly well.

This issue is a known issue with MM and they may or may not tell you to not enter a BG when asked to get it to calibrate.

The best advice I got from MM is to skip a few “Enter BG” massages before entering a BG so that is it during a time when my BG is flat.

Patience is the biggest challenge with the CGM.

Thank you for this. I’m waiting for the trainer to get back to me as her manager was going to review my reports to see if my trasmitter might be faulty. I had read about so many having trouble with calibrating that I wasn’t sure how it would go when we first strated. however, the trainer put us on a schedule of when her BG is usually stable and when to calibrate: waking up, 3:30pm and around 10-11pm. The first 2 weeks were so smooth, I couldn’t believe it.

Thanks for all the help everyone. I hope to hear from the trainer today.
Have a great day!

Thanks for explaining. I will give it a try the next time my sensor. Thanks again.