Dexcom G6 versus Dexcom G7

Has anyone else noticed that the Dexcom G7 is not as accurate as the Dexcom G6, at least in the fist 24 hours? I have had to calibrate the G7 every time I’ve put a new one on. I just don’t trust the results. And I’m talking huge differences in the results, as much as an 80 point swing. But if I calibrate, the G7 usually fixes itself. The person at Dexcom said I may have to wait as long as 24 hours before the G7 rectifies itself, but I usually see the correction much sooner than that. I guess my biggest gripe is that I don’t feel as comfortable using the results of the G7 to make bolusing decisions as I did with the G6. Is there anyone else out there with the same problem? And then there’s the overpatch situation. But I won’t bore you with that right now.


Totally normal CGM behavior and normal to be worried about it. Have you heard of presoaking? From the glossary topic:
Pre-soak: the practice of inserting a new CGM sensor up to 24 hrs before the current sensor session expires, allowing it to acclimate to the body before activation. This is intended to ameliorate erratic readings in the first 24 hrs of a new sensor session.

Here’s a topic where people discuss ways to handle to first hours-day results with a G7.

G7 timer starts at insertion. So if you presoak you lose that time.

I agree. G7 does not seem as accurate and takes 24 hours to settle down when I change to new sensor. I do a lot of finger sticks. I think G6 was better device but can’t beat no warm up time. I was annoyed at over patch. FSL had better adhesive by far. But I think but have no proof that Dexcom has improved its adhesive. I use a little SkinTac and haven’t used over patch for months. And all sensors have stayed on with no problem.

I thought the ‘warmup’ timer starts at insertion, but the 10 day wear timer doesn’t start until you enter the code and ‘start’ the new sensor.

Ten day count down starts at insertion.

rrrruff, Just order the AZEN overpatches from Amazon. A pack of 60 for the G7 is $6.99 and they are awesome. I’ve had T1D for 20 years and have tried a lot of products and this is a winner.

Thanks to all who replied with their recommendations. I really appreciate all of your help.

What exactly is good about a faster warmup time if the readings are useless the first day?


I went back to G6 after a few months of the G7. The few perks don’t outweigh it being completely useless the first day. Granted the G6 isn’t completely accurate the first day either, but while it may be 20-30 off the first day, the G7 can be 80-100 off. Called Dexcom after it reading a constant LOW for 7 hours (was at 122), they refused to replace it and told me not to make treatment decisions the first 24 hours on ANY G7 sensor. So in reality it’s a 9 day sensor and that’s if nothing else fails. The G7 is one step forward and two steps back and it’s sad that people are defending this nonsense.


Makes sense. But also like the size. And not having to deal with transmitter. I made the change last year. And am mostly happy.

Jane Cerullo

@rrrruff For the most part, my G7 readings have been pretty accurate after insertion. Every once in awhile, I get a reading that is wildly off - like you said +50 mg/dL (or more) - which has happened like when the sensor says I’m having an Urgent Low, and when I check with a finger stick, I’m not. Now that I think about it, that’s the only time I do check, so maybe it is slightly off the other days after insertion, but the beginning inaccuracies just doesn’t matter as much to me. – I have done random tests for accuracy (like a few days after a wild reading) and the G7 is pretty dang accurate!

I was forced to move to G7 a couple months ago by my supplier. I hate it! G6 worked beautifully for me for years. Sure, inaccurate reading for a day or two, but solid after that. G7 has been a nightmare. I was sent 9 sensors for my 3 month supply, all from the same lot. The first two I tried were so off (waking me over and over for false lows till I had to turn them off). they sent me replacements. They told me not to calibrate during the first several hours. Then, no more than a couple more times during the sensor session.

Next sensor sort of worked, but was never as accurate as the G6. The replacements also sort of worked, but I was using twice as many test strips which are out of pocket for me. By then I was looking at Freestyle Libre 3, and my doctor simultaneously suggested I switch to it. I did. First two Libre sensors (also inaccurate for the first day or two) leveled out to solid gold info. Yay!! And they last 14 days each, were easy to apply.

But then I got my second set of Libre 3 sensors and neither of their auto injectors would open. My husband can do 30 pull ups and all his strength wouldn’t budge them. Got out the channel locks! Nope. Epoxied shut?? Libre is sending us replacements which is good. Meanwhile I tried another of the G7 sensors. It wouldn’t pair, said call Dexcom for a replacement which I’ll do today. Finally another G7 sensor did pair, but the #s are off enough that for days 1-3 I’ve had to meter test for insulin decisions. Working better today. Ugh!!

Footnote, We’re sending in the glued Libre sensors so they can figure out what happened. If it’s sabotage, or some factory glitch.

I have experienced the same thing and I dread the 24 hours after inserting a new sensor. My biggest problem is being awakened at night with false alarms. I guess it’s something we have to live with since we don’t have a better choice.

False low alerts happened for me during the first night after insertion of the G6. I have the same issue with the G7. With the G7 I use the Quiet Mode to silence the low alert for up to 6 hours. This helps a lot. During the time I had the G6, I did not come across the Quiet Mode.

Ok. My two cents. In reading thru this forum both T1 @ T2 and on the FaceBook post. More people have been having more problems with the G7 versus the G6.
I personally hope they don’t discontinue the G6 . No reading = you got to far away from your phone or receiver Loss of signal I’ve had them with the G6. But these receiver were traced back to Twain made. Never with US Made. And I’ve had no shipping issues sense changing from a Arizona Dealier.

Mark27 is right. I always presoak and with the 12 hour grace period at the end I think the G7 is a winner. I have not seen anything in the readings that would make me think that the G7 is less accurate than the G6. My A1C has remained the same, a good indication that the readings from the G7 are good.


That has not been my experience or others as I browse the topic. The countdown starts at insertion time.

Since I only presoak for 1-2 hours, I might not notice (thanks to the 12 hour grace period) that is has timed out at the insertion time and not the start time.

I haven’t found the G6 or the G7 to be accurate. I use it because I have hypoglycemia unawareness. I use finger sticks for insulin dosing.

Don’t forget CGM is measuring interstitial glucose, not blood glucose.