Guardian 3, Calibration not performed

Overnight last night I kept getting calibration alerts. I did one, bolused and then every 15 minutes it would alert again and say “Calibration not performed”. I’ve never had this happen before. Not sure if it’s a sensor issue or a transmitter issue. Status says the transmitter is fully charged, as is the pump. This was while I was in bed when the pump on the same side as the sensor… No interference from a cell phone or anything.


How about calling Medtronic tech support.

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Sounds like the notorious Calibration Loop. There’s a new transmitter out that’s supposed to fix this. If you don’t already have it, contact Mdt and they’ll send you one. But meanwhile the advice I’ve seen is to hold off from giving it the BG for an hour or so and it will clear.

I don’t know if you’re on Facebook but if you are there’s a very good 670 support group that has files condensing their collective wisdom on various issues including tips for escaping the Dreaded Loop.

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Completed my application for a replacement transmitter about three months ago. Just got an e-mail from Medtronic today advising that I should receive the replacement within a few days. As life goes, I haven’t been in the loop for several months.

If you need a link to this, go to:

I have had the same problem, and even though I can’t say I have tried the new transmitter yet (but I should be receiving it before the end of the month), I think it will save us a lot of calibration frustration (should we make that a new term in the Diabetes community?).

Some other things I have found to help are:

  1. Do not do a calibration & bolus at the same time. Let it do & finish the calibration first, and once the calibration is finished, enter the bolus manually. This will allow it to do the calibration without worrying about a changing BG.
  2. Do a minimal number of calibrations (probably about 3 for most people). Do the calibrations at (approximately) the same time each day (if possible). Hopefully with these things managing to keep you in Auto Mode, your numbers will usually be reasonably good, so at meal time, just enter the carbs without even doing a BG (unless you are significantly high or low).

Something I have noticed about the sensor & transmitter in bed is that the numbers can sometimes be a little less accurate (usually lower) when I get up in the morning. They usually get better after 15-20 minutes. Something that I try to do (I don’t know if I can claim to always do a good job of it, but I try) is wait until I have been out of bed for at least 15-20 minutes before doing a calibration.
Hopefully some of this helps, and hopefully the new transmitter helps as well.

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I called them as well, and they were completely stumped. Nothing they suggested worked. They are sending me a new sensor, hoping its just that and not the transmitter. :confused: We shall see…

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I’ll try this! I usually only calibrate after I am dressed and about to leave the house, before lunch and when I go to bed, maybe 50% of the time I do it at dinner. I don’t go out of auto mode very often, so this is weird to me!