Replacing Dex transmitter & sensor: order of operations? (iPhone)

I have a Dexcom G6 and a Tandem t:slim; I use an iPhone with them. Tonight (yeah, I know I’m late asking, but this will be useful in the future) I need to install a new sensor and transmitter. I’m trying to figure out the proper ORDER of steps, such as: insert new sensor and transmitter in my body; pair transmitter with pump; pair transmitter with iPhone; start new sensor session.
I’ve made mistakes in the past. I’ve wasted at least one sensor and at least one transmitter (had to buy a new one out of my own pocket). I managed to shut down a transmitter shortly after installing it, wasting its entire 90 days.
The problem is, the two companies aren’t willing to deal very much with each others’ products, so there’s no step-by-step instruction sheet for doing this combined operation; you have to piece one together for yourself from the three or four instruction sheets/manuals comprising the two sets of instructions.
Does anyone know of a single document, downloadable preferably, that details how to do this all in one list of steps? I don’t wanna waste another transmitter!
–Keith

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I found this on Tandem site, points out the order to get pump and phone app set up with new transmitter.

From Tandem:
"The Transmitter ID field will be grayed out on your pump if you have an active CGM session. You will need to select STOP SENSOR on your pump before you can edit the Transmitter ID.

Note: If you are using the Dexcom mobile app and the Tandem pump, we recommend pairing your Transmitter to your pump first, then pairing it to the Dexcom mobile app. Once the Transmitter is paired to both devices, you will be able to start a CGM session on either device."

My transmitter is also ending soon and the above steps is how I typically do it.

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@K_Hjalmar you have asked a question circulating since the problem was born.

@MM1 has given you good information. You situation is not clear. I will provide support sharing I have used a pump & Dexcom (various models) for 20+ years. I have been using the Tandem Control-IQ technology and a Dexcom G6.

The official answers from Tandem and Dexcom are murky. Dexcom sites say, “primary display device” or “medical device” first. Hold on, slam on breaks. This is contradictory because most folks use their phone as primary yet the pump or Dexcom receiver is the medical device. Tandem is equally rooted in a conundrum.

Here is what has worked for me for the past 19 months of CIQ usage:

CGM changeout.

Everything starts on the pump because it is the ‘medical device’ and the primary display device even if a phone is used personally as the primary device. This is further emphasized because a pump and dedicated Dexcom receiver cannot be used simultaneously as the Dexcom receiver is classed as a medical device.

Pick your best time. Your best time should be when the CGM report shows level data and you are not planning a meal or generally needing to bolus during the following two hour window. This means select a time when you have a 3 hour window of usually level CGM reporting.

For me, 7:00PM is the best time to have level CGM reports and the time is free of BG changing activities for me.

If I am doing a sensor only, I change sensors at 7PM. At 6:55, I get everything read, do a skin prep and insert the new sensor by 6:58.

At 6:59, I go to my phone and stop the sensor, then to the pump and begin the stop and start at 7:00. As soon as the pump is done, I go to the phone and repeat the process. I enter the code on each.

I sit back and watch, assuring both the pump and the phone are playing nice together.

If it is a transmitter, again it is the pump that is the key player.

I start at 6:55 by stopping the transmitter session on the phone then the pump and start the new transmitter and sensor on the pump from transmitter to sensor.

Once things are going on the pump, on to the phone and repeat the process.

About 7:10 with either a new sensor or new transmitter and sensor, I verify both the pump and phone are playing nice.

Here are links to the information supporting this supportive recommendation:

Hope this helps.

For an experiment, I just did the following today, an odd situation!!

I have Tandem and phone with xDrip.

My “old” transmitter is on day 108, with sensor on day 9.
I wanted to start new transmitter today, due to busy schedule tomorrow. But wondered if I could keep current sensor reading to xDrip, and use Tandem to start new sensor with new transmitter.

And yes, I was able to stop sensor on tandem, and as hoped, the xDrip kept reading bg from original transmitter.

“Stop” did not really stop the old transmitter from sending data, since phone/xDrip is displaying it. I think the pump just stops asking for it when stop sensor was done.

Then I inserted new sensor, new transmitter, and started on tandem pump. Now in warmup, but still getting readings on xDrip on phone, from original sensor/old transmitter, while tandem still in warmup with new transmitter and new sensor.

Warmup done. First reading 106 on pump for new sensor/trans, 109 on xDrip phone for old sensor/trans.

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xDrip won’t work on iPhones .

Correct.
But if you are using 2 devices (tandem pump/receiver and phone with app or xdrip), it would still work.

I wonder how Clarity will sort out the discrepancy :thinking: ?

@Jimi63 , what discrepancy are you speaking of with Clarity?
It uses the every 5 minute report from the CGM.

@MM1 has 2 sensor sessions running concurrently. Clarity will have an issue with inputs from 2 data sources

I don’t use Clarity, so can’t confirm. I load to Tandem T:Connect for combined pump and cgm data.

But if data is sent with bg value and timestamp + transmitterID, from each sensor/transmitter I had active, it should be fine getting both values. But Clarity can only load from dexcom app or receiver, not tandem pump.

I had both running for just a short time, as the old transmitter was reading the last values before it ended, and 2nd sensor was started with new transmitter.

It depends on what data Clarity stores together. If trans id is included, it would make both readings unique, and not cause issue.

OK, I’ve got a few new bits.

  1. I tried pairing the transmitter on both pump and iPhone (pump first), before doing the actual sensor insertion and activation (on the phone, as usual). It worked! I waited the two hours, and data started up on the iPhone right away. On the pump, though, I had to click “Start session” (even though I had done so on the phone); fortunately, it gave me the option of skipping the entry of the sensor code, and started displaying data (after a couple minutes: not right away).
  2. I checked the Dexcom User Guide (duh! I gotta learn to at least look at the manuals! But Mac owners kind of get out of the habit…), as cited by Jay6 above. Behold and 'lo, Dexcom advises us to pair one device, then start the sensor session on that device BEFORE pairing the transmitter on the other one! Which I didn’t do this time, I think. Or maybe I did.
  3. This whole process is still a bit murky. Dexcom told me (direct from a rep in a chat) to pair the transmitter with the iPhone first before the pump; Tandem’s instructions say to pair the pump first. I’m guessing either would work, so long as you don’t start the session before pairing with at least one device.
  4. A final bit of mystification: on Tandem’s two-page quick-reference brochure of how to both change a transmitter and a sensor (which I had never seen before: thanks, Jay6!), we’re told a single transmitter can’t be linked with both a pump and the Tandem receiver (and by extension, I assume that is true for an iPhone if you’re using that instead, right?) at the same time. Surely that’s wrong, isn’t it? I think I have it linked with both right now, don’t I? Or is data going to the pump, and THEN to the phone?! I didn’t think it worked that way. PLEASE correct me if I’m wrong!
    I truly wish the two companies would get together and jointly issue a clear set of instructions! But in chats and phone calls, neither company is willing to talk about much of anything that involves the other. I understand this is likely due to legal concerns, but it doesn’t help us users.
    Thanks to everyone who replied! It was helpful.

You might know… I found out one other bit of confusion. The Dexcom manual has me enter the sensor code first, then the transmitter SN! ??? I’m sure I got into trouble once doing it in that order. Help!
–Keith

The transmitter can pair with one phone and one device (non phone). Devices include a dexcom receiver or a tandem pump.

Not sure what you mean by Tandem receiver, but the X2 “acts” like a device (non-phone) when paired to dexcom transmitter.

Tandem users can also use T:Connect app (and web version with more history) , which communicates to X2 pump, displaying both pump and cgm data, no direct access to transmitter/sensor.

I do all my dexcom stuff on my pump and the phone just picks it up.
The only issue is a new transmitter which I need to do on both.

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@K_Hjalmar have you gotten a good answer?