G7 startup overlap?

  1. Each Dexcom G7 has its own transmitter.

  2. When a G7 sensor expires, you have a 12-hour grace period where it will continue functioning. (Which is really nice.)

  3. When you insert a new G7 sensor (if I read correctly) the sensor session/warmup starts automatically.

All that together, unless I’m mistaken, means you can have two sensors going at the same time. The old sensor expires. You put in a new one. You wait half an hour. That’s when you stop the old sensor and pair the new one, which should have completed its warmup.

Does that work?

I suppose if the new sensor does need to be paired, and you’re using a pump, you can pair the sensor with your phone first, wait for warmup, and then switch over on your pump. You have to pair them separately anyway, since it’s a new transmitter. That would even let you make sure warmup is successful (and compare readings from both sensors) before changing the pump over to the new one.

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Correct with a couple caveats… a) G7 sensor warm up begins when you take the top off the applicator, and b) you don’t need to pair it to make it warm up - only to see the results.

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I don’t pair the new sensor for hours because dexcom, for me, is a little inaccurate the first few hours. I let it sit 4-5 hours then pair the new sensor and stop the old one. When the new one pairs it uploads all the data since warmup so you see 2 lines on the dexcom app.

I find the G7 to be very inaccurate during the first 12+ hours, always with false low readings (when compared to blood tests and how I feel). I had the same exact problem with the Libre system. I’ve been applying a new G7 sensor when the 12 hour grace period starts on the old one (last day of wear). I’ve had luck pairing the NEW sensor to my Dexcom phone app while I DON’T yet pair the new sensor with my G7 receiver and that lets me see both sets of numbers simultaneously. However a couple of times doing this forced my old sensor to switch off. It seems to work if I pair with my phone first. If I pair with the receiver first, the receiver seems to send a message to my phone that the older sensor has been replaced and it stops working, forcing me to pair the new sensor to the receiver. I recommend if you’re going to try this- to NOT pair with any device for several hours, to give the new sensor time to “warm up” before the old one shuts down. Also be aware that Dexcom recommends that you NOT calibrate a new sensor until it’s been worn for 12 hours. Which just proves (to me at least) that the readings are unreliable during the first 12 hours. The G7 is otherwise very good, I just rely on fingerprick testing during the initial 12-24 hours until it “settles in”.

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I had the same problem with the G6. And the Guardian 3 sensors before that. I’m only on my second G7, but so far it’s been warming up smoothly for me. Hopefully that keeps up. (I’d cross my fingers, but I’m Jewish.)

The problem I’ve been having is that with the sensor in my arm instead of my belly, and the transmitter being smaller, the pump is much more liable to lose the signal. I’m gradually learning how and where to keep it, especially at night.

But good to know you can keep both sensors going. I think I’m going to try that when this one expires.


@WearsHats I just activated my new sensor after wearing it for 6+ hours. Here’s the graph you can see there are double lines and zero gap for warmup (which happened before lunch)


I remember the first time my chart showed double the dots from G7 sensor transitions. I thought the app was broken so I called Dexcom support. They had no clue either but were able to see my double readings on their side. As we were trouble shooting it I noticed the dots were on different 5min reading patterns. This lead to tracking when first and second sensor was installed and then mapped them to the different sensors. Took a good hour to figure it out! But that was in Feb 2023 when G7 started shipping.


I’m still using the G6. But I wear a pump holder arm band at nite on the arm with the sensor. Seems to work well for me

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I now place the Dexcom G7 sensor on the inside of my arm. It’s less likely to get bumped that way, and I have less bruising. I can still feel on my arm where previous sensors were placed.
How long does it typically take for a previous sensor insertion site to heal?

Mine are fine the next day but I don’t have any kind of bruising. A bruise is going to take a week +

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@savejf, Am interested in learning more about the inside of your arm use. Where did u install it… on the bicep or tricep muscle? How consistent are your readings? Do you get reading jumps (up or down) that come back? How long have you been doing it?

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Hi Gmershon,
I just started using the inside of my arm. The readings are very consistent. I place the sensor on the inside of my arm so it rests next to my body and it isn’t in either the bicep or tricep.
Good luck!

@savejf, the furthest on the inside my arm I’ve placed G7 is where it barely touches my side when my arms swing while walking. It’s basically on the edge of my tricep. Once I missed the tricep and had bleeding under sensor with 10 days of wonky readings. Am wondering if I was unlucky hitting a vein, or if I moved it further to the inside of my arm.

According to Dexcom:
… G7 sensors may be inserted on the back of the upper arm (indicated for users ages 2 years and older) or the upper buttocks (ages 2-6 years old). Don’t wear your Dexcom G7 sensor on other sites as it may not work as expected. If you wore G6 sensors on your abdomen, wear G7 sensors on the back of your upper arm.
(hilights are mine)

I’m still using G6 and wear my sensor in a variety of locations, but keep in mind - if you have an issue and call to request a replacement Dexcom might refuse if you are not using their approved sites. Wear it where it works best for you but be prepared if you have to make a call.

Hi Dorie,
I was told to use the inside of my arm by a Dexcom representative for the G7 placement. It works well. If I were to receive unusual readings after first 24 hours then I would test with my meter. Based on that, I would consider choosing a different site and asking for a replacement sensor.

I wear the Freestyle Libre 3 and have the same issues with it being inaccurate the first day. So after reading comments on this forum, I tried the method of applying a new one and letting it “soak” before I removed the old one. Got much more accurate results this time!


I’m finding that the G7 often takes several hours to properly “wet” before it gives accurate readings. It regularly reports false lows when it first warms up. So I’m now pairing the new sensor with my phone and watching the readings, leaving the pump connected to the original sensor during the grace period. Only when the readings from the new sensor approach agreement with the old sensor do I switch the pump over.

@joe what program are you using that lets you keep two sensors paired at once? Neither the G7 app nor the Tandem pump will let me keep both, and I had trouble getting Xdrip to work with the G7 sensors. (I have Xdrip pulling data from the Dexcom cloud instead.)

no I don’t pair the new one for 6-12 hours. I just apply it and forget it’s there while in the “grace period” of the old one. I pair the new one when the old one dies.

the 2 traces are because the new dexcom “backfills” the data up to the moment it is paired. it uploads all of it’s data since it started and it appears as 2 graphs on the standard Dexcom phone app. It gives me a sense of if the new one is reading crazy. Yes there is a chance that the new one won’t pair, but if that happens you can try a strong magnet (there’s a spot you can tap with a magnet which should activate it) or replace the sensor with another one.

Paul @WearsHats, I have dual readings on my Clarity page, but different from what Joe described. When I decided to begin with the G7 and not sure what to expect as possible change from G6 I began an experiment where I started both a new G6 and G7 at the same time. Both started at 2:30 PM.

The G7 began showing readings after 28 minutes - the first few very realistic although I thought too low having just finished eating [70 gm] less than 2 hours before. After about 30 minutes of getting readings, the G7 dropped to 58 [fingerstick 171] and stayed low for half hour and shot high. By 5:30, three hours i, both were reading 112 and stayed relatively close, with some delay for 6 days until the G6 went kafluy - so bad that I junked it and at thus point I paired the G7 with my t-Slim for CIQ.

Both the 6 and the 7 were in “Dexcom preferred” location on my body - G6 abdomen and G7 triceps and both sensors displaying on my phone lockscreen 24 hours per day With both increasing and decreasing BGL, there was a lag of 2 or 3 reading on my G7.

The more interesting observation, is the G7 is “more gentle” with rapid rising - and less apt to trick CIQ into giving an unneeded correction bolus. As example, one of my common breakfast selections, 52 gm carb, is oatmeal cooked in 8 oz milk with a side glass of OJ and mug of coffee - I begin eating less than 10 minutes after bolus and within 30 minutes often get a G6 reading with 2 arrows up - when using both sensors, I’d get a very similar number on the G7 with only and angled up single arrow. It appears to me, that Dexcom corrected its reporting program; yet, when analyzing data from each device, separately, over a few consecutive days both my TIR and average glucose were the same.