Tandem Mobi + Dexcom G7: setup and real life
Pairing the Mobi with the G7, the 15 Day sensor question, taming overnight alerts, fixing connection dropouts, and what the community wishes it knew sooner.
5 min read
The Mobi plus G7 combo is one of the most popular closed-loop setups going, and for good reason: tiny pump, fast-warmup sensor, Control-IQ+ doing the heavy lifting. The official setup is genuinely easy. This guide covers the setup in brief and then the stuff the manuals skip: alerts, dropouts, and daily wear.
Pairing, the short course
Update first if you're on older software
G7 compatibility arrived via a free remote software update. If your Mobi has been in a drawer or you're switching from G6, check for the update in the Tandem Mobi app before anything else. Tandem's official walkthrough is here: How to set up your Dexcom G7.
Grab the pairing code
The 4-digit code is on the G7 applicator and also shown in the Dexcom app. You'll enter the same code in two places: the Dexcom app and the Tandem Mobi pump app.
Start the sensor session on the pump side
Enter the code, start the session, and let the 30-minute warmup run. Tandem's start and stop a G7 session guide covers every screen. Once readings flow, Control-IQ+ picks them up automatically.
The 15 Day sensor question
The Dexcom G7 15 Day now works with the Mobi and t:slim X2, a change that rolled out quietly enough that most people learned it from an email. Before you switch, know the fine print: the 15 Day is cleared for ages 18 and up, while the standard G7 covers ages 2 and up. Parents of younger kids are staying on the standard G7 for now. The community thread on it is worth a skim: Tandem Mobi/Dexcom G7 15 Day.
Alerts: the actual learning curve
Ask the community what's hard about this setup and nobody says pairing. They say 3 a.m.
The thing to internalize: you're running two devices that each want to tell you things, and by default they'll both tell you the same things. The fix is deciding which device owns which alert. Most people let the pump handle what the pump can act on and quiet the redundant layer, then set overnight alert profiles deliberately instead of living with the defaults. The Sleep Activity setting in Control-IQ+ also runs a narrower target range overnight, which reduces the situations that trigger alerts in the first place. Walk through your alert settings once with fresh coffee and your care team's input, and the 3 a.m. problem mostly evaporates.
When the pump loses the sensor
A classic failure mode: the Dexcom app shows readings fine, but the pump says no CGM. Since the app sees the sensor, the sensor is fine, and the fix lives on the pump side. The usual ladder, in order of effort: check the pump's Bluetooth connection screen, stop and restart the CGM session on the pump with the same pairing code, restart the pump app, and keep pump and phone physically close for a few minutes while they renegotiate. A parent wrote up the full troubleshooting saga, worth reading before it happens to you: G7 stopped communicating with the pump.
Daily wear notes
The Mobi is small enough to disappear: clip, adhesive sleeve, or literally a coin pocket. It's fine to disconnect briefly for showers, hot tubs, and contact sports; heat is the bigger enemy than water, so don't leave it baking somewhere hot while you soak. One honest heads-up from recent community experience: some infusion set styles have hit backorders, so keep a comfortable buffer of supplies and reorder early rather than at the last box.