Dueling Dexcoms: 2 transmitters, 1 iPhone, 1 receiver

Turns out my husband has had some strange numbers lately. I have a dex G5 and ditched my receiver for my phone as soon as I got it. By ditched, I mean I stored it in a drawer. I wondered if it would be possible to sync the old receiver with a new sensor and transmitter that my husband could wear for a few days to make sure his bg is stable? Is this possible to do…even while I still wear a sensor and transmitter synched to my iphone?

If I understand clearly what you mean… Yes:-)

What I understand:

You have a sensor and a transmitter paired to your iphone. At one time, your receiver was paired to the same transmitter.

You would like to pair your receiver to a new transmitter and sensor, on your husband, while your phone is still paired to the old transmitter and sensor.

You can do that! In fact, I did just that with my son when the old transmitter was almost dead, to check accuracy between two locations:-) So I had two transmitters running on him at the same time, with two different sensor locations. Once was going to the receiver, and one was going to the iphone.

The only thing you need to keep in mind is that, in order to enter the new transmitter number in the receiver, you need to stop the old sensor. You will lose a couple of hours of CGM information while your old sensor is restarting, until you get the request for the two consecutive glucose meter measurements.

So, the sequence of what you have to do is as follows:

  1. install the new sensor on your husband, with the new transmitter
  2. stop the old sensor with the receiver
  3. enter the new transmitter SN in the receiver
  4. start the old sensor again with the iphone
  5. start the new sensor with the receiver

And - bingo!

Let us know what you find with your husband - hopefully, it is absolutely NOTHING. Also, let me know if something in these instructions did not work out:-)


Well, this is so helpful!! Thank you!!!

You are like Dr. Dex.

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Dex is my middle name. Except I am a lefty (dexter = right hand – as we lefties all know, sinister = left-handed --> persecution --> Freedom to all lefties! --> All lefties unite!).

We LOVE our Dexcom! It has changed the way we live with diabetes in our household.

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Michel, I know you have nothing else to keep you busy at the moment, so how about a Diabedia series on Dexcom Tips and Tricks? You seem to be a wealth of knowledge.

I would love to write a series like that! That’s a great idea. As soon as the site is launched I will take it on.

I can share all the tips and tricks we have learned about the dex - but I have lots of gaps. A lot of people on this forum have plenty to contribute in the area, so I figure we could put up a great category there!

I’ll make any contribution I can to this category as well. I’ve had the good fortune to have worn a Dexcom continuously since about a month before the first Dexcom was released eleven years ago. (I was in one of the last pilot studies before FDA approval).
The Dexcom has literally saved my life, and I would never consider being without it.

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Thanks, @Michel, for making this all clear! Now my hardest obstacle is convincing him to give it a go for a few days.

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Quick follow up question…if the receiver was never paired with the current transmitter I am wearing (that original transmitter’s battery died long ago) would I still need to restart the one I’m wearing?

Probably not, right?

Hmm. I have never tried that.

I am pretty sure the answer is NO, because the only reason for stopping it is to allow the receiver to have access to the transmitter ID. Recently I had to enter a new transmitter SN into the receiver after months of not using it, and I know I did not need to stop a sensor. I wish I could remember exactly what I had to do - I think the only thing I did was to go into the settings and change the transmitter SN, and that was it.

Clarification, btw: the method I gave you in the earlier post was the one that I discussed with Dexcom, and that they agreed was the right one. It may be that another method also works. Now I am wondering if it is possible to make it work without ever worrying about stopping the original sensor at all. I’ll have to experiment.

No, you just enter the transmitter serial number of the transmitter you want to connect with and you’ll be good to go.

It’ll take 10-15 minutes for the receiver and transmitter to connect with each other, then it will ask you to start the sensor. Wait the two hours and enter the two calibrations.

All of this should have no effect on the sensor you are currently wearing. The software that controls all of this is in the receiver, not the transmitter. The transmitter will just keep sending out a raw reading every five minutes to whichever device(s) it is paired with.

EDIT: With the Dexcom, the transmitter only transmits, it does not receive any data from the receiver. The receiver will only receive the raw data from the transmitter, and it too does not transmit any data. If you want the received data further transmitted you need the phone.

So, the transmitter has no idea that the sensor it is attached to has just been inserted or is about to expire. All of that is contained in the receiver software. And the receiver never talks to the transmitter, it can’t.

If you use xDrip+ this all becomes very apparent. Even when my sensor is warming up my watch, which I have acting as my receiver, still gets a reading from the transmitter every five minutes.

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