# Glucose alerts on iPhone: lows, highs and how to hear them at night

> Dulce has low and high alerts with your own thresholds, plus rapid change, predictive low and a critical low alert for 55 mg/dL or less, all under Settings → Alerts. They are regular iPhone notifications, so they follow silent mode and Focus: at night, turn silent mode off and allow Dulce in your Sleep Focus. Keep your sensor app's own alarms on too, because Dulce is an extra layer, not a medical device.

URL: https://dulceglucosa.com/en/blog/glucose-alerts-on-iphone  
Author: Giorgi Khimshiashvili  
Published: 2026-10-19  
Updated: 2026-10-26

A glucose alert has to do two things at once: wake you when it really matters and leave you alone when it doesn't. If it goes off for everything, you end up muting it, and then it's useless. This guide covers every alert in Dulce, its defaults, and how to tune it so it helps without wearing you out.

> Dulce doesn't replace your sensor's alarms. If you use FreeStyle Libre 2 or Libre 3, keep the Libre app's alarms on; with a Dexcom, keep the Dexcom app's alarms on. Dulce is an extra layer, not the only one.

## Where to set them

Everything lives in Dulce under **Settings → Alerts**. During setup Dulce asks for permission to send notifications. If you declined it, turn it on in the iPhone Settings app under Dulce → Notifications.

## The alerts, one by one

| Alert in Dulce | What it does | Default |
| --- | --- | --- |
| Low glucose alert | Warns you when glucose drops below your threshold (50 to 80 mg/dL) | 70 mg/dL |
| High glucose alert | Warns you when glucose rises above your threshold (140 to 300 mg/dL) | 250 mg/dL |
| Critical low alerts | An alert on a severe low (55 mg/dL or less) that ignores quiet hours and snoozes | On |
| Rapid change | Warns you when glucose rises or falls very fast | On |
| Predictive low | Warns you when you're heading for a low | Off |

### Critical low: the one Dulce never holds back

It's the only alert that comes through Dulce's quiet hours and snoozes. It always uses the **Alarm** sound and repeats every 5 minutes while you stay below. You can turn it off, but Dulce asks you to confirm: it's the alert that matters most at night.

### Hearing alerts at night

Dulce's alerts are regular iPhone notifications, so your iPhone decides whether they make a sound. With the ring/silent switch on silent, or a Focus such as Sleep that doesn't allow Dulce, an alert arrives without sound. To hear a low at night:

- Keep silent mode off and the ringer volume up.
- If you use the Sleep Focus or Do Not Disturb, add Dulce to its allowed apps (Settings → Focus).
- Keep your sensor app's own alarms on too.

### Predictive low

It looks at how fast your glucose has been falling over the last few minutes and warns you if, at that rate, you'll cross your threshold soon. To avoid firing on sensor noise, it only warns when several readings in a row are falling. It doesn't tell you what to do: it suggests checking your sensor. It's off by default, and when you turn it on Dulce explains exactly that.

## Keep alerts from wearing you out

- **Quiet hours.** Pick a window (say 11 p.m. to 7 a.m.) when non-critical alerts are muted. Critical lows still come through. It's off by default, so nobody loses a night-time high alert without deciding to.
- **Alert frequency.** How often the same alert can repeat while you stay out of range. Every 15 minutes by default. Severe lows always repeat every 5.
- **Snooze alerts.** If you know you'll run high for a while (after a meal, say), pause alerts for some minutes or hours. Severe lows still come through. You can also snooze straight from the notification.
- **Sounds.** Choose one sound for low glucose and another for high: Default, Soft, Chime, Pulse, Alarm or Silent. Two different sounds tell you what's going on without looking at your phone.

[Set up your alerts in Dulce](https://apps.apple.com/app/apple-store/id6770694596?pt=127601978&ct=blog_alerts&mt=8)

## Do they arrive with the app closed?

Yes. They don't depend on Dulce being open: Dulce's server checks your readings (from LibreLinkUp or Dexcom Share) and sends you the alert. With Dulce Pro it does this every minute; with the free version, every 5 minutes. A Dexcom shares a new reading every 5 minutes, so with a Dexcom alerts follow that rhythm; see the [Dexcom guide](https://dulceglucosa.com/en/blog/dexcom-on-apple-watch-and-lock-screen).

If you wear an Apple Watch, iOS sends the alert to the watch when your iPhone is locked, and it taps your wrist. More in the [Apple Watch guide](https://dulceglucosa.com/en/blog/how-to-see-cgm-glucose-on-apple-watch).

## Alerts for your family

Your followers can get their own alerts when you go low or high, with their own quiet hours, and very low readings always reach them. See the [family sharing guide](https://dulceglucosa.com/en/blog/sharing-cgm-glucose-with-family).

## If an alert doesn't arrive

1. Check that Dulce's **Notifications** switch is on and that iOS allows notifications from Dulce.
2. Look at the time of the last reading in Dulce. If it's old, the problem is that no data is reaching LibreLinkUp: follow the [LibreLinkUp no-data guide](https://dulceglucosa.com/en/blog/librelinkup-not-working). With a Dexcom, check that Share is still on in the Dexcom app.
3. Check whether quiet hours or snooze are on.

## FAQ

**Can glucose alerts ring when my iPhone is on silent?**

No. Dulce's alerts are regular notifications and follow your iPhone's sound settings, including silent mode and Focus. At night, turn silent mode off and allow Dulce in your Sleep Focus. The critical low alert does come through Dulce's own quiet hours and snoozes.

**Does Dulce replace the Libre app's alarms?**

No. Keep your FreeStyle Libre 2 or Libre 3 alarms on. Dulce is an extra layer, not a medical device.

**Do alerts arrive with the app closed?**

Yes. Dulce's server checks your LibreLinkUp readings and sends you the alert: every minute with Dulce Pro and every 5 minutes with the free version.

**Can my family get my alerts?**

Yes. Your followers can get their own alerts when you go low or high, with their own quiet hours, and very low readings always reach them.