This post may contain affiliate links. Please see the affiliate disclosure for more details.
If your kid runs a Dexcom on an iPhone, the phone is a medical device now. It is also a phone – which means it fills up with games, silences itself during class, and quietly kills the app in the background to save battery. Every one of those normal iPhone behaviors can cost you an alert.
Key takeaway: most missed-alarm complaints are phone settings, not sensor problems. A twenty-minute pass through the settings below fixes the majority of them.
Not medical advice. Always follow Dexcom’s own setup instructions and your care team’s guidance for alarm settings and treatment. Settings menus move between iOS versions, so the exact path may differ slightly on your phone.
Storage / Background / Critical Alerts / Focus & Silent Mode / Bluetooth / Battery / iOS Updates / Medical ID / Controls / Wallpaper
Storage Space
Dexcom requires open storage space to run and work properly. Check your storage space and delete any unnecessary applications if necessary.
A phone sitting at 100 percent full is the classic cause of an app that “just closed itself.” Kids fill storage fast with video and games, so this is worth re-checking every few months rather than once. Go to Settings > General > iPhone Storage and look at the bar at the top. If there is no comfortable headroom, offload a couple of big games before deleting photos – games are re-installable, photos usually are not.
Background App Refresh
The Background App Refresh setting on an iPhone allows the Dexcom app to refresh when on Wi-Fi or cellular in the background even when you are not using the app. Make sure this setting is turned on at Settings > General > Background App Refresh.
Two traps here. First, the master switch at the top can be set to Wi-Fi only – if it is, the app stops refreshing the moment your kid leaves the house, which is exactly when you want it working. Set it to Wi-Fi & Cellular. Second, the per-app list below the master switch has its own toggle for Dexcom, and it can be off even when the master switch is on. Check both.
Critical Alerts and Notifications
This is the setting most worth your time. Dexcom can request permission to send Critical Alerts, which are the notifications allowed to break through silent mode and Focus. If that permission was never granted – or got reset by an update – a low alarm at 3 a.m. can arrive completely silently.
Check Settings > Notifications > Dexcom and confirm notifications are allowed, that Critical Alerts is on if your app version offers it, and that alerts are set to appear on the Lock Screen. While you are there, make sure the alert style is a persistent banner rather than a temporary one, so a notification that arrives while the phone is face-down does not vanish before anyone sees it.
Then test it. Follow Dexcom’s own instructions for triggering a test alert, put the phone on silent, and confirm you actually hear it. An untested alarm setting is a guess.
Focus, Do Not Disturb, and School Mode
Focus modes are the newer version of Do Not Disturb, and schools increasingly encourage a School Focus during class hours. That is fine – as long as Dexcom is on the allowed list inside every Focus your kid actually uses, including Sleep.
Go to Settings > Focus, open each mode in turn, and add Dexcom to allowed notifications. Sleep Focus is the one people forget, and it is the one that matters most at 3 a.m. If your kid sets their own Focus modes, re-check this after any phone handover or major iOS update.
Bluetooth
Old transmitters that remain as paired devices can effect your phone’s battery efficiency. Unpair old transmitters in the Bluetooth settings.
After a year or two of sensor changes, the Bluetooth list can hold a long tail of dead transmitters. Forget the ones you no longer use, and leave Bluetooth itself on permanently – turning it off from Control Center to save battery is one of the most common reasons a sensor “loses signal” for hours.
Battery Settings
Low Power Mode throttles background activity, which is exactly the activity a CGM app depends on. A phone that spends every afternoon under 20 percent is a phone that will miss readings. Charging habits matter more than any setting here: a car charger and a charger in the school bag solve more alert problems than tweaking options does.
iOS Updates
Do not let a medical-device phone auto-update the moment a new iOS ships. Dexcom publishes which iOS versions and phone models are compatible, and there is usually a gap between Apple releasing a version and the app being validated on it. Turn off automatic iOS updates on your kid’s phone and update deliberately, after checking Dexcom’s compatibility list.
After any update that does go through, re-check notifications, Focus, and Background App Refresh. Updates are the single most common reason settings you already fixed quietly revert.
Medical ID
Help first responders access medical information from a locked iPhone screen by setting up your Medical ID. This feature on your iPhone details allergies, medical conditions and emergency contact information.
Fill in Type 1 Diabetes as a medical condition, list insulin, note any devices worn, and add at least two emergency contacts. Turn on Show When Locked, otherwise none of it is reachable by someone who finds your kid without you. This takes five minutes and is the highest-value item on this page for a kid who is starting to go places alone.
Parental Controls
Review the parental control settings to make sure your child’s phone is being used as intended.
One caution specific to T1D families: Screen Time downtime limits can block apps during set hours. If you use downtime, add Dexcom to the always-allowed list so overnight limits never touch it.
Wallpaper
Set the wallpaper on a locked iPhone screen to denote the phone is being used as medical device. View a sample wallpaper posted on Pinterest. Download the Pinterest file to your phone and use the phone’s picture markup tools to add other pertinent details like your child’s name, parent’s phone number or an “if found” phone number.
The ten-minute version
- Free up storage so the phone is not sitting at full
- Background App Refresh on, set to Wi-Fi & Cellular, Dexcom toggled on
- Notifications allowed, Critical Alerts on, persistent lock-screen banners
- Dexcom added to every Focus mode, especially Sleep
- Old transmitters forgotten, Bluetooth left on
- Automatic iOS updates off
- Medical ID filled in and shown when locked
- Dexcom exempted from Screen Time downtime
- Trigger a test alert with the phone on silent and confirm you hear it
Doing this at the start of each school year, and again after any big iOS update, catches almost everything before it becomes a missed low.
Related on Diabetes Amigo
- CGM hub – choosing and living with a sensor
- Make a Dexcom stick for 10 days
- New Year organization – other clean-up and organizing tips
- T1D back to school boxes – the rest of the school-year reset
