What do many alarms do to your sleep?
Each alarm wakes you for a moment. Between the alarms, you get short pieces of light sleep.
- In a 2022 laboratory study with 10 students, the snooze alarm prolonged wake time and light sleep in the last 20 minutes.
- In a 2024 laboratory study with 31 habitual snoozers, 30 minutes of snoozing cost about 6 minutes of sleep. It improved or did not affect cognitive tests on rising.
These studies used a snooze function, not separate alarms. The effect on sleep is likely the same, but no study has confirmed this.
How do the alarm setups compare?
| Setup | Effect on sleep | When it is useful |
|---|---|---|
| One alarm at the latest time that you can get up | Unbroken sleep until that time | You get up reliably at one alarm |
| Many alarms, 5 to 10 minutes apart | Light, broken sleep from the first alarm | You like to wake in steps and you are not late |
| One alarm and one backup, on a second device | Unbroken sleep, with a safety margin | An important day, such as a flight or an exam |
| Many alarms across one hour or more | A long period of broken sleep | Not recommended. An earlier bedtime is the better fix. |
Why do people set many alarms?
Most people do it for safety. They do not trust one alarm, or they do not trust themselves. A 2025 study of more than 3 million nights found that 55.6% of sleep sessions ended with a snooze. Repeated alarms are a common habit.
There are two different fears:
- The alarm fails. A backup alarm on a second device solves this. See why an iPhone alarm has no sound on iOS 26.
- You stop the alarm and sleep on. More alarms do not solve this. You stop each of them in the same way. See why you turn off your alarm in your sleep.
When are many alarms a warning sign?
If you need 5 or more alarms each day for a long time, you possibly sleep too little. The US National Heart, Lung, and Blood Institute gives 7 to 8 hours a day for adults.
Speak to a doctor if you sleep enough hours and still cannot wake up, or if you are very sleepy in the daytime for weeks.
What can you do instead?
- Move your bedtime earlier, until one alarm is enough.
- Set one alarm for the latest time that you can get up.
- Add one backup alarm on a different device for important days.
- Make the alarm harder to stop with no attention. See how to stop snoozing.
Waker is an iPhone alarm app that uses one alarm and a conversation. There is no snooze button. When your alarm rings, you tap “Talk to Waker” and talk about your day. If you go quiet, Waker speaks up again, up to three times. Waker is not a very loud alarm, and it is the wrong tool if you do not hear alarms. No study has tested if a conversation replaces the need for many alarms.
Common questions
How many alarms is too many?
There is no researched number. If the time between your first alarm and the time that you get up is longer than 30 minutes, you lose unbroken sleep that an earlier bedtime or one later alarm can give you.
Is it better to set one alarm or two?
One alarm gives unbroken sleep. A second alarm on a different device is a sensible backup for important days.
Do many alarms make you more tired?
The studies do not agree. See is snoozing bad for you.
Why do I sleep through all of my alarms?
The frequent causes are too little sleep and an alarm that is too quiet. See why you cannot wake up to your alarm.
Sources
- Effects of using a snooze alarm on sleep inertia after morning awakening. Ogawa and colleagues, Journal of Physiological Anthropology, 2022.
- Is snoozing losing? Why intermittent morning alarms are used and how they affect sleep, cognition, cortisol, and mood. Sundelin, Landry and Axelsson, Journal of Sleep Research, 2024.
- Snooze alarm use in a global population of smartphone users. Robbins and colleagues, Scientific Reports, 2025.
- How Much Sleep Is Enough. National Heart, Lung, and Blood Institute.