Dexcom G4 forcing upgrade to G6

I received an email from my Pump manufacturer, Tandem, today. They’re saying that Dexcom is going to force G4 users to upgrade to the G6, with the exception being device integration (e.g. my tslim G4 use means I stay on G4- no problem).

The reason I’m posting this is I keep seeing FUD (fear, uncertainly, doubt) around the 'forced ’ migration to the G6 and wanted to post some real info on it.

tl;dr: G4 standalone users are going to be forced to G6, G4 integrated users are not.


what exactly is the nature of the fear?


From reading other posts, there does seem to be a level of anxiety (fear??) among some of the G4 users who want to stick with the G4 as long as possible and do not want to be “force upgraded” to the G6.

Which is understandable. I am always a fan of choice.


My daughter was told just a few weeks ago that she would not be forced to upgrade.

And yet there are people who are very angry because Medicare isn’t going to let them get a G6 next month. sigh. Me, I’m one of the few (seemingly) who is happy with what I have


For the record, here’s tandem’s email:

Dear t:slim G4™ Pump users,

Our records indicate that you currently use Dexcom G4® PLATINUM continuous glucose monitor (CGM) integration with your Tandem pump. We have received a number of questions from users like you following the recent announcement of Dexcom’s new G6® CGM system.

The new Dexcom G6 system is not compatible with your pump. If CGM integration on your pump is important to you today, we recommend continuing to order the CGM supplies compatible with your device. Dexcom plans to continue shipping their G4 PLATINUM CGM sensors and transmitters for people with integrated devices.

Dexcom is requiring their G4 users to upgrade to G6 UNLESS they indicate that they are using it with an integrated device. There are no products currently on the market that are integrated with the new Dexcom G6 sensor. Please make it clear during your next CGM supply order that you use an integrated Tandem pump to ensure you continue receiving the CGM supplies that work with your device.

As always, please feel free to call us at 1-877-801-6901 if you have questions.

Kind regards,
Tandem Diabetes Care

First - I am not questioning you.

Obviously true.

Tandem really doesn’t know what Dexcom will do. Tandem can make their best guess and use the most current information relayed to them from Dexcom. But make no mistake. Dexcom (a $7 Billion company) is not going to be told by Tandem (a $400 Million company) what they can or can not do.

(BTW - That is great that Tandem is up to $400 Million - they are doing great!!! But hey - Dexcom is playing in the big-time leagues.)

Not quite. This is the most current understanding that Tandem has of the situation.
Not exactly the same thing.


I doubt Tandem is shooting from the hip on this- they’ve got to be getting their info from Dexcom, right? They don’t gain anything by guessing.

I use the G4 with an integrated system, the DIY Loop automated insulin dosing system. If the above assertion is actually true, I wonder if G4 suppliers are going to be put in a position to identify who actually uses an “integrated” system.

At this point, considering the economics (sensor restarts, transmitter life up to 9 months) and performance (longer radio range than the G5, fewer data dropouts, and similar accuracy or MARD as the G6), I think the G4 is the sweet spot for me.

I think Dexcom will make a public relations blunder if they try to determine that only the commercially integrated systems are eligible for continued G4 supply. We shall see.

Things are fluid and can materially change. If someone figures out how to workaround the hard 10-day G6 sensor life, that could fundamentally impact my current assessment.


While I certainly see your overall point, I just wanted to call out the MARD of the G5 and G6 is significantly better than that of the G4. The G4 is ~13% and the G5+G6 are both around 9%.

Source. Page 10.

That is true for the early G4 Platinum system. There was a firmware upgrade in 2014 called the “505” that made the MARD of the G4 equal to the G5. I use the 505 firmware.

Here’s a quote from the linked source.

Now, Dexcom G4 PLATINUM is the first and only CGM system on the market with a single-digit MARD (Mean Absolute Relative Difference) measurement, below 10 percent. MARD is the standard industry measurement of accuracy, where a lower MARD reflects higher accuracy.

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AH that’s right! My bad. I actually had a G4 at the time, and now you say that I remember the update and the big difference. Apologies.

Interesting that Dexcom chose to use the pre-update MARD for that deck I linked to from Feb 2018. Perhaps made the story/graph look better.

I love Dexcom as a company. But I realize that they’re not perfect and their internal marketing forces will stretch the truth to benefit them. That slide you reference obscures the relatively small incremental improvements from my G4 505 vs. the current G6.

As a user of their products for nine years now, I don’t value the improved inserter and the no-cal features as others might. I’ve never been representative of an average user or diabetic.

If I did use the G6, I would choose to calibrate since I remember reading that the MARD falls to the 7% range, a significant improvement in my book.


Totally agree.

Biggest reason for us to switch to the G6 will be integration with Tandem.
Optional G6 Tandem update towards the end of this year
The G6 would be required to utilize the Control-IQ (Hybrid Closed Loop) Tandem update expected first half next year.

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I 100% believe that Tandem simply flips whatever communication they get from Dexcom to the users.

As Terry states, I believe the situation is more fluid over at Dexcom then Tandem would have you believe from that letter. The bottom line is this is all up to Dexcom.

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Oh, I see what you’re saying. :+1:

Just to be clear, it falls to 7% on the G6 if you calibrate?

I linked to some slides in this post:

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Here’s a snapshot of the pertinent slide from @Tim35’s link above.

I think calibrating the G6 once per day is worth a MARD of 7.2% overall and 7.3% on the first day.


Thanks guys- that’s great info!