Dexcom CGM vs Meter reads - getting back in sync

For the most part, my Dex 3 has been right on with cgm and meter reads…but occasionally i get some sync issues.

I got a tip yesterday from Dexcom technical support…regarding Dex saying 190 and meter saying 120. Tech Support said and claims to have had some success with the following ‘fix’

When this is discovered…upload your meter read to Dex…15 minutes later take another meter read and upload again. Within 30 minutes the Dex algorithm should get back in sync and be more in line with meter reads.

Issue - depending on how far off Dex is—you know the occasional runaway reading–the kind where the trend starts on a rapid pace up and then just keeps going and going and going…Dex says 367 and you are actually 180…uploading meter reads at this point will cause and OUT OF CALABRATION X–in those cases, the suggestion was to separate yourself from Dex for 30 minutes to 1 hour…move the receiver to a different room so there is no transmission - no ‘Y’. After 1 hour, meet back up with Dex and get your first read—many times you dont even need a finger stick - apparantly the algorithm ‘fixes’ itself. But if you are still way off, but not so much to cause a giant X out of calabration, then you can do the double read mentioned above with a 15 minute pause in between.

This doesnt happen that much to me…but when it does it can be very frustrating…especially when i am on my way out the door and dont want to drag my meter along.

by the way - i am never quite sure if this is the best place to post this stuff - are people checking this forum out? would the main forum be better? should i keep my tips to myself? hmmm… opinions please.

Keep the tips coming - this is a good one, which I ‘kinda’ knew, but it’s helpful to see it in writing.

Dexcom 3 in April 2006
Dexcom 7 in July 2007


This is very handy. I’ve had this kind of problem only a few times, but it’s really annoying when it happens. Thanks.

When Dexcom reads WAY higher, it’s usually because of water underneath the Transmitter. Even the ‘SEVEN’ sometimes leaks and lets water under there, and the reported numbers go high. So the first thing to do is unclip the Transmitter, check if there’s any wetness near the contacts, and if so, dry off everything.

THEN: Yes, Dexcom takes double-calibrations within a one-hour more seriously than singles, and it should come back to reality pretty quickly if it wasn’t wet. The 15 minutes gap is important, though, because Dexcom does try to account for the delay between ISF glucose level and bG when it handles a calibration, and it’s more effective to hit it with another “adjustment” reading AFTER it’s had time to see that even after the lag, it’s still reading high.

In the case of water damage, though, it’s often better to just perform the fake throw-away and restart completely, with the two hour delay… those really bad differences between the Dexcom and meter readings during that period should NOT be allowed to control any calibration changes… and unless you either restart the Sensor, or swap meters after it’s all over and DON’T plug in ANY meter before Dexcom is recovered, they’re gonna be looked at and used.

Hi Molly,

I’m brand new to this network and this group. My wife is the T1DM in our family and we are considering an investment in a Dexcom Seven. So we want to get as many viewpoints as possible to guide us to a good decision.

Please continue your sharing on this Group. CGM tips on the CGM Group make sense to me.