670G: When do you calibrate?

As any CGM user knows, calibrating is both required and a pain in the butt. All the models I have used require that it be done at least once every 12 hours. For a while I was having lots of problems with my 670G, including an excessive number of Enter BGs and my numbers being of by more than expected, even though I was doing them every 12 hours. After finding someone on support that actually seemed to be experienced enough to be helpful, I was given the following advice:

  1. Don’t calibrate too often (at least 6 hours between, preferably closer to 9)
  2. Only do what it asks (for Enter BG messages and boluses, do not do a calibration)

When I started following these recommendations, everything was great, (much fewer Enter BGs and more accurate numbers). The only problem was the fact that managing to following these guidelines was hard to do with my current schedule. My usual BG/eating schedule is the following:

9:00am-10:00am Breakfast
4:00pm OR 6:00pm-8:00pm Dinner (depending on the day)
10:30pm-11:30pm Bedtime Snack

If I do calibrations at these times (since I do BGs at these times anyway), it would mean the following amounts of time between calibrations:

Breakfast-Dinner: 6 to 11 hours (all, at least barely, within the 6-12 hour recommended time between calibrations)
Dinner-Bedtime Snack: 2.5 to 7.5 hours (usually outside the 6-12 range)
Bedtime Snack-Breakfast: 9.5 to 11.5 hours (all, at least barely, within the 6-12 hour recommended time between calibrations)

I can obviously try to work around this problem by doing 1 or 2 extra calibrations, but obviously we all want to do as few as possible. What kind of calibration schedule do you use? Does your schedule require you to do separate BGs for calibration? Just curious as to what everybody else does to get the most out of their CGM.

I use this schedule, and for the most part my finger sticks are within 10pts of the CGM.
Good point about entering only the BG and NOT calibrating when it asks for BG. I learned that one the hard way.

12PMish (i skip this one often because of work schedule)

Rarely does the 670 ask me for a BG when using this schedule.

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I wish I had your schedule, having 2 times that are exactly 12 hours apart probably makes it easier to adjust the others (although we all probably have some trouble). I think the one that I have trouble with is the fact that I go to bed and get up approximately 12 hours apart, so if I go to bed early and/or get up late it makes it more than the maximum of 12 hours, which would require doing a calibration during the night. Even if I put the stuff by my bed, the chances of waking up in the middle of every night is not likely. I guess I’ll just have to put more effort into when I go to bed and wake up to make it work. Something I might try doing is doing my morning calibration & correction bolus at 7:00am (since I need to get up to take other medication at that time anyway) and then waiting until I actually eat to do the bolus (without doing a second BG).

That’s a downside to the way the Guardian CGM works. Without that calibration @ the 12th hour, it give you NO readings, vs as I recall the DEXCOM will continue to give you readings. It’s annoying, and to a degree dangerous if you happen to have forgotten your BGM which I have done on occasion… you end up flying blind until you can get to a BGM.

As for scheduling, its not that I have time… I’m on the move most of the day. I simply make time, and test wherever I am.

Yes, I’ve grown entirely too dependent on my CGM.

There is an issue with the Guardian 3 sensors and I was told from my medtronic reps that a fix is coming soon. I found that when it ask me for a calibration that when it just starts it the asks for another BG right when the Cal starts I manually put the BG back then it ask it ask to us it for Cal and I say yes and then everything is fine. Day 1 on a new sensor is crazy day 2 thru five not bad and day 5 and last day intermittent senor readings I swap out. Don’t Calibrate if the sensors readings and your BG are far apart as it wont be excepted and ask you again for a calibration and if you do it will expire your sensor out which happened to me 4 hours after it was first inserted. there are so many other work arounds. If you get frustrated just shut off smartmode play with manual mode to get the two readings closer together then go back into smartmode.

just my 2 cents

I LOVE that I am not FORCED to calibrate Dexcom every 12 hours. Yes, there is a reminder, but I’m not forced to calibrate. I do it when I feel I should. I’ve had the Medtronic sensors in the past (UGH!!!) and was truly aggravated at the loss of data if I missed THEIR calibration request. That is truly a lousy thing (IMO)

wholeheartedly agree with you on that @Dave44
I miss my Dexcom in that respect. If you miss a calibration with the Guardian, you fly blind until you have access to a BGM.

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I calibrate when it asks, except for when I know the next calibration will be in the middle of the night at 2am or something, then I calibrate before bed.

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And therein lies the heart of one of the issues I have with the MM CGM–you MUST calibrate or you get NO DATA. I went thru a year with Enlites and HATED how I’d get no data twice a day, when it wanted a cal. Who the heck wants to be a slave to calibrating when the system REQUIRES it? To get no CGM data just because it wants a cal is ludicrous. I can go days if I want to, without calibrating the G5. It still shows data, and it’s usually accurate enough to be useful and SAFE, even when I skip the 12-hour calibration by many hours.

@Dave44 does that mean you go days without doing a glucose test?

no, it means I can go a day or two without calibration. One can test without it being a calibration, but I don’t test much any more. there is little need for testing as the G5 is USUALLY very accurate. And when it seems like it isn’t, JUST GIVE IT 15 MINUTES. LOL!

That is correct. Here is a link to get a replacement transmitter:
Some things that I have learned can help are to minimize the number of BG and calibrations. One thing that I started doing that I had never done before is to do calibrations on a set schedule (except, of course, when starting a new sensor), in my case this ended up being 7AM, 3PM, and 11PM (you may end up using different times). This keeps the calibrations as far apart as possible, but still within the 12 hour requirement. And instead of doing a BG at every meal, I just did a bolus based on the carbs (unless my sensor number was high or low, in which case I did a BG for the correction bolus, but I still didn’t use it as a calibration). These changes made a huge difference for helping me keep good numbers (not to mention doing less BGs was finger friendly!), as well as make it easier to stay in Auto Mode. Hopefully they can help you as well, and hopefully once we get the transmitter upgrade that will help as well. Good luck!

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From the Medtronic website: