Why Your Phone Alarm Is Not Going Off and How to Fix It

Published 2026-10-16 · Marion Phone Repair

You set an alarm on your phone, you are certain it was set correctly, and it never went off. You overslept, missed an appointment, or were late to work. This is one of the most frustrating phone problems because the alarm app is supposed to be the most reliable function on the device. Here is every reason this happens and how to fix each one.

Common causes on both iPhone and Android

The alarm volume is separate from the ringer volume

On many phones, the alarm volume is tied to a specific audio channel that is separate from the ringtone, notification, and media volumes. If you turned down a volume slider and accidentally adjusted the alarm volume, the alarm may fire at zero volume — technically it went off, but you could not hear it.

iPhone: Alarm volume is controlled by the Ringer and Alerts slider in Settings, Sounds and Haptics. It is NOT the volume you adjust with the side buttons unless you enable Change with Buttons in that same menu. Many people turn down the side buttons for media and assume the alarm is still loud — it may not be
Android: Open Settings, Sound and Vibration (or Sound), and look for the Alarm volume slider. It is a separate slider from Ringtone, Media, and Notification volumes. Make sure it is turned up

Do Not Disturb is silencing the alarm

Both iPhone and Android have Do Not Disturb and Focus modes that silence notifications. In most default configurations, alarms are allowed through DND. However:

iPhone Focus modes: If you created a custom Focus mode, check that Allow Alarms is turned on in the Focus settings. Some custom configurations can block alarms
Android: In Do Not Disturb settings, there is usually an Alarms exception. Make sure alarms are set to Allow. On Samsung phones, check the Allow Exceptions list in DND settings

The alarm was set for PM instead of AM

If your phone uses 12-hour time format, it is easy to accidentally set an alarm for 6:00 PM instead of 6:00 AM, especially when setting it quickly or late at night. The alarm is set and active — just for the wrong time. Switch your phone to 24-hour time format to eliminate this possibility: Settings, General, Date and Time on iPhone, or Settings, System, Date and Time on Android.

Battery optimization killed the alarm app

Android phones aggressively manage background apps to save battery. Some manufacturers (Samsung, Xiaomi, Huawei, OnePlus) are especially aggressive about killing apps that run in the background. If the system kills the alarm app's background process, the alarm will not fire.

Samsung: Go to Settings, Battery and Device Care, Battery, Background Usage Limits. Make sure the Clock app is not in the Sleeping Apps or Deep Sleeping Apps list
Other Android: Go to Settings, Apps, find your Clock or Alarm app, Battery, and set it to Unrestricted or Not Optimized. This tells the system to never kill this app's background process

This does not apply to iPhones — iOS does not kill the built-in alarm app.

The phone was powered off or died overnight

If your phone battery dies during the night, the alarm cannot fire. Some phones will power on automatically when an alarm is due, but most will not. The fix is simple: charge your phone overnight. If you are concerned about battery health from overnight charging, modern phones manage charging intelligently and stop drawing power when full.

iPhone-specific fixes

Bedtime or Sleep Focus overriding alarm sound

If you use the Sleep Focus schedule in the Health app or Clock app, the wake-up alarm uses a different sound and volume setting than regular alarms. The wake-up sound may be set to a gentle tone that is too quiet to wake you. Go to Health, Sleep, Full Schedule and Alarms, and check the alarm sound and volume. You can also set a regular Clock alarm as a backup instead of relying on the Sleep schedule alarm.

Alarm sound set to None

In the Clock app, each alarm has a Sound setting. If it is set to None, the alarm fires silently (it will vibrate if vibration is on, but make no sound). Tap the alarm, tap Sound, and select an actual alarm tone. Pick something loud and distinct — the default Radar tone is one of the most effective for waking people up.

Android-specific fixes

Third-party alarm app issues

If you are using a third-party alarm app instead of the built-in Clock app, it is more vulnerable to being killed by battery optimization, cleared from memory, or broken by an OS update. The built-in Clock app has system-level privileges that third-party apps do not. If your third-party alarm is unreliable, switch to the stock Clock app for critical alarms and use the third-party app as a secondary.

App cache or data corruption

If the Clock app itself is acting erratically (alarms set but not firing, alarms disappearing, the app crashing), clear the app cache: Settings, Apps, Clock, Storage, Clear Cache. If that does not help, Clear Data (this will delete all your saved alarms, so note them first). Then recreate your alarms.

Software updates

Some Android OS updates or security patches have been known to reset alarm settings or break alarm functionality temporarily. If your alarms stopped working after an update, clear the Clock app cache, restart the phone, and recreate the alarms. Check for a follow-up patch that may fix the issue.

Best practices for reliable alarms

Set two alarms: Set your primary alarm and a backup alarm 5 minutes later. If the first one fails for any reason, the second is a safety net
Use the built-in Clock app: It has the deepest system integration and is least likely to be killed by battery management
Charge your phone overnight: A dead phone cannot alarm
Test after changes: After updating your phone, changing DND settings, or switching alarm apps, set a test alarm a few minutes in the future to verify it works before relying on it for a morning alarm
Use 24-hour time: Eliminates AM/PM confusion entirely
Check volume before bed: Make the alarm volume slider part of your bedtime routine

Phone alarm help in Marion

If your phone alarms are consistently unreliable and the fixes above have not resolved it, Marion Phone Repair can check your phone for software issues, battery management settings, or app conflicts that may be preventing alarms from firing correctly.