So now I have a question about calibrating: If it’s time to calibrate and I check my blood sugar and my meter and my CGM are only 2-3 points different, do I even need to calibrate?
@Suzanne17
Good question.
I think different people have different approaches.
Our approach is to add the calibration when asked (if BG level) for the first two days.
Once on day #3, we typically drop down to one calibration per day (which certainly goes again Dexcom/FDA procedure) but it seems to work for us. Downside is you then get the nag screen about needing to calibrate but aside from that the system appears to still work fine.
At a certain level, it comes down to what you are comfortable with.
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I use the Dex receiver for some activities instead of the iPhone and like to be able to glance at it. It requires another push of the button to see past that big nag orange blood drop on the screen when it wants a calibration. The only way to make it go away for good (for 12 hours) is do a calibration.
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I calibrate sometimes just to stop the annoying orange drop screen from obscuring my glucose reading, even if it matches very closely with my finger stick. Other times, I go for more than 12 hours past the calibration time, because I get into the habit of hitting the button 2X in quick succession to get to the glucose reading, provided that I still trust it’s numbers (which I usually do). Even past a week of wearing a sensor, it’s often within 3 points of a meter. Even overnight.
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Ok! Thank you, Tim, John & Dave 
I have already calibrated (because it asked me to) a couple of times when my meter was within just a few (2-5) points of my CGM, then the next reading on the CGM was 10 points different. Then I thought, “What was the point in that? NOW it’s off!” I’m just trusting it is doing what it’s suppose to do and I have figured out (I think) that my glucose is really running about 15 minutes behind my CGM anyway. As long as the arrows are pointing me in the right direction, it seems to be helping me head off extreme highs and lows and has already alerted me to fast dropping lows in the night - which is one of my main concerns. Much appreciation for your experienced words.
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Yes, sometimes the slope of the graph is as useful as the current glucose reading. Oftentimes it is MORE useful in predicting an impending low. I think we all might tend to just quickly glance at the number and ignore the graph. I know I do that and sometimes that turns out to be unfortunate for me, as I tend to get low a lot. I’ve changed my eating habits so drastically the past few weeks to the point that repeated reductions in basal settings and changes to the ISF and I/C ratio need to be addressed for the 3rd time. When I’m a bit low, I can’t sit down with my spreadsheet and do what needs to be done. I’m OK to be typing this, but not clearheaded enough for doing calculations. (maybe later tonight–I’ve got to get my pump reprogrammed before bedtime)
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Hi! I’m glad it is going well for you. It sounds like things are leveling out and you are having a good experience. I wanted to say that I’ve been using a CGM for almost 3 years(Medtronic though) and it took me a good several months to get the hang of it. At first I was like, “what a worthless piece of junk! what’s the point???” But now I can’t imagine the D life without it. I love the arrows- like you said. It puts everything in perspective when I’m about to head out for a walk and I’ve got triple or double down arrows! I love also that I don’t have to stay high for very long either. It’s totally changed my life. Even if and when my CGM can’t keep up with what my BG is actually IS at that moment it provides me with enough information to make better decisions about how to treat or when to just be patient. Dexcom is extremely accurate but there are times when our BG is rising or declining so fast the CGM needs time to “catch up.” That doesn’t mean there is a technology failure. If your Dex says 144 and major up arrows and your BG on your meter is almost 200 well then it’s working its way up and will alert you soon. Don’t get hung up on the meter and dex being the exact same all the time. Looks like lots of people have given you great info. for calibration and use. I’m so happy with CGM. I can’t hardly understand why anyone wouldn’t want to use it!!!
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Hi Tim, I’m intrigued by your calibration approach. Do you drop down to one in order to avoid having to do an unnecessary fingerstick or, for you, does starving the dex of a calibration on day 3 and beyond actually improve the dex’s accuracy?
Thanks, Thomas
@Tnyc
More of the former.
lol
Seems to be just as good (for us anyway - your experience may of course vary) either way so more or less, “why bother”.
IMHO, if only doing once per day calibration, first thing in the morning is an ideal time as the BG is often level plus you then have the absence of the “calibration nag feature” for the next 12 hours.
I think the only way the accuracy would be improved is if you really can’t find a good time to get the second calibration in with a level BG. Calibrating with a rapidly rising or falling BG for your “second of the day” is probably going to be less helpful as opposed to just skipping it and going with the “one per day” with a BG that is in range and level. Obviously this goes against the Dexcom procedure and the FDA approved process. But it seems to work for us.
I just started on the G5 last fall and I am questioning the accuracy of my meter as well. I have a linked One Touch Ping meter and Animas Ping pump, so if I get a questionable meter reading (great variance from the CGM and the CGM direction arrow is straight), I wash my hands with soap and water and retest. If that one is wildly off - and it is often 20 to 30 points higher or lower- I do a third test and take the best out of two results. I have found that there is a delay with the CGM - it measures interstitial fluid not blood glucose, and as I am sensitive both to insulin and to metabolized carbs - it can take the CGM a good 15 minutes to ‘catch’ up with where the blood glucose was so I am learning that it is best for me to use the glucometer and CGM together. The direction arrow is significant! Also, the first 2 days with the CGM are so inaccurate- and it doesn’t matter how many sensors I have used - that I would never feel comfortable using the CGM for dosing. By the end of the week it is in much better alignment but I do wish it would keep a closer alignment earlier on. Perhaps when I have to change my pump I will get a new meter and give the Contour a try. The most valuable feature of the CGM as far as I am concerned is knowing what direction your glucose levels are going and then I can double check with my meter if I am worried about going too high or too low. Oh, the joys of being brittle:-) (and yes, I know the term is considered obsolete, but it is my reality so I use it).
All models of Contour Next meters are very accurate. I’ve used a ton of meter of various brands since the mid-1990s and this one has to be the best of all of them for accuracy and repeatability. Maybe that helps explain why I have such great luck with the G5. I only use Contour Next meters for calibration and of course for all other testing
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Thanks Dave, I appreciate the information. I’m definitely going to go take a look.
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