Dexcom numbers after warm up

Hi all…I am new to Dexcom and Slim X2…I am a former user for the Medtronic 670 G and guardian sensor…
I have found with my Dexcom my number are ridiculous the first day after warm up…most times I have to calibrate, which is frustrating…and I don’t trust my numbers…which starts this vicious cycle of my continuously checking my number via finger pricks…Does anyone else experience any of this?

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Hi @Morgan84 yes. The first 2 to 8 hours my dex screams that in 42 and I’m going to die in 20 minutes. I only calibrate when my bs is steady for an hour or more, I like to calibrate first thing in the morning. Dexcom is actually very good in my experience after that and for the rest of the session with no real need to calibrate after that.

CGM reads 20 minutes behind reality. So if I’m dropping and I’m going to eat and my dex says 149 and a finger stick says 80 I don’t calibrate. If I just had juice and a finger stick said 139 and my dex is saying I’m still low I don’t calibrate. That just adds noise.

Yes for me I still test by finger stick those first few hours and then about 2x on day 2 and then pretty much none after that.

CGM don’t always work for some people. CGM can be flaky when I’m dehydrated. They can be more or less flaky if I use my arm because it’s fairly lean. But I have to say after using gen 1-3 guardians that Dexcom is the best I’ve used.

As with all things diabetes, you’re experience may be different. Good luck :four_leaf_clover:

Morgan, like you I recently switched from the 670G to the Tandem/Dex combo. You will find lots of helpful information on this site to ease your transition.

One suggestion I found to be of great benefit was to insert a new Dexcom sensor early. This allows the sensor to “acclimate” to your body before placement of the transmitter. I have found about 12 hours before expiration of the old sensor works well for me. So, you will have two sensors at the same time for a while. When the old sensor expires, remove it and place the transmitter in the other sensor and you are good to go. I find the readings to be accurate from the start when I use this method.


@mcpaulus , thanks for this tip! I’m going to try that on Friday.

Morgan @Morgan84 I hear your frustration.

For me, I sometimes notice some questionable readings within the first few hours of starting a new sensor, but I don’t let them bother me too much. Very rarely do I think that the readings [the complete readings , meaning the arrow directions and four consecutive numeric readings] need verification by a finger-stick. Knowing the G6 provides “anticipatory” readings and trends, I only calibrate when arrows have been horizontal for ar least 25 minutes and finger-sticks during that period have been unchanging and considerably different from the sensor.