Question about Dexcom CGM with TSlim pump

My brother has beenlooking into getting a new pump. He’s currently on an old Medtronic pump, but is using a Dexcom CGM. He met with both Tandem and Dexcom reps and, somehow, he is of the opinion that if he uses the Tandem with the Dexcom, he’d have three sites on his body. He thinks the “third” site is needed for the two devices (pump and CGM) to communicate with each other. Could this possibly be true?

Another question…when he met with the Tandem rep, he was shown how to fill the reservoir, but said he had a lot of trouble doing so. But…he can’t remember if he had his reading glasses with him. I’ve read on here that some people do have trouble filling the reservoir…is it something you quickly get used to?

Thanks to any of you who can provide me with some information…I am not the most up-to-date technical person here!

No, that is not true. You only have two. Dexcom sensor and Tandem infusion set.

It’s different, but not difficult to use. The difficulty is more about accepting change. If he expects it to work like medtronic, he will be disappointed.


The Tandem pump talks to the Dexcom transmitter the same exact way the Dexcom transmitter talks to a receiver or smartphone. Wirelessly, via Bluetooth. There is no extra hardware required nor anything extra attached to you. Depending on what infusion set he uses, he may even be able to maintain the same exact sites he’s using now.

I’ve gotta parrot @Jim26 about the cartridge. It’s not difficult at all, but it is very different. How resistant to change is he? It takes on average 66 days to reform a habit. It may benefit him to watch and copy a YouTube video while he’s forming the new habit. After you do it a few times, though, it really does become second nature. The pump even walks you through every step except the actual injecting the insulin into the cartridge bit.

Tandem also has a customer support line with nurses that are there for training assistance, and will walk him through the steps over the phone.

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The reservoir filling might be a challenge if your brother has dexterity issues

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I agree with your statement that cartridge changes could be challenging for people with dexterity issues. I don’t have those type of issues and can still struggle sometimes with my changes every 3 days.
I also was not happy about the cartridge change versus my Medtronic changes. It does take longer but now after 5 years, it is my new normal and I don’t think about it.
Side note here. I Amin a clinical trial with a Beta Bonics pump. And the cartridge change is challenging. But I know like the Tandem, I would get use to it being my new normal after a little while. The glass cartridge is very small. The top where the syringe goes in is small. The insertion of cartridge with infusion set is challenging trying to line it up. But like switching from Medtronic to Tandem, switching to Beta Bonics would have that same learning curve.

Although it’s discouraged you can prefill cartridges for him and leave in fridge. I know a family with a young kid who does this.

There are three pieces; the infusion set, the transmitter and the sensor. However, the transmitter snaps into the sensor and is experienced as just one site. Maybe that is what he is thinking of. I just switched from Medtronic and am liking the T-Slim very much.

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Thanks everyone for your answers. He’s thinking about using the newer Medtronic pump and keeping his Dexcom. He’ll set up a meeting again with each rep and then make a decision. But he does now understand that there are only two sites with Tandem/Dexcom, just like he has now with Medtronic/Dexcom.

Thanks again!


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