By the Rise team · Updated 28 October 2026.
Sleeping through an alarm can mean the sound does not wake you, or that you snooze and do not remember deciding to. That groggy stretch is sleep inertia. The Cleveland Clinic says it usually lasts 15 to 60 minutes, and longer if you are badly sleep-deprived. Not enough sleep can make it worse. If the grogginess continues even when you sleep enough, or it lingers through the day, talk to your GP.
In short
Two things get called sleeping through an alarm. One is not waking to the sound. The other is waking just enough to snooze, then not remembering the decision. Sleep inertia is the name for that groggy stretch. The Cleveland Clinic says it usually lasts anywhere from 15 to 60 minutes, and that it can last longer if you are badly sleep-deprived.
Not enough sleep can make that grogginess worse. It is not, on its own, proof that you slept through the sound. The Cleveland Clinic says not getting enough sleep can cause or worsen sleep inertia. Hilditch and McHill, in a 2019 review, describe sleep inertia as the grogginess felt on waking, and say it is worse under conditions of prior sleep loss. In the studies they review, performance on waking was significantly worse after a night of partial sleep deprivation than after an 8-hour sleep opportunity. The same review says sleep inertia has also been measured under well-rested conditions, with effects lasting at least an hour in some of those studies. The Sleep Foundation says most healthy adults need between 7 and 9 hours of sleep each night, though the exact amount varies by age, health, and other factors.
The Cleveland Clinic says it is harder to wake up during NREM stage 2 than during NREM stage 1. It says short bursts of brain activity in that stage, called K complexes, help you sleep through noises. It also says you are most likely to experience sleep inertia if you wake during NREM stage 3, the deepest stage. Sleep inertia there is how groggy you are once you are awake.
Whether deeper sleep makes that grogginess worse is less settled. Hilditch and McHill call the evidence mixed. Stampi, as they cite him, found a 41% drop in performance after waking from slow-wave sleep, compared with before the nap, while waking from lighter N2 sleep looked similar to people already awake. The review notes that older slow-wave stage 4 is now classed as N3. Other studies found no link between sleep stage and performance after waking, and the review says this association may not be as robust as initially thought. That is grogginess after waking, not a claim that deep sleep stops you hearing the alarm.
Sometimes the alarm did wake you, and you snoozed while half-asleep. The Cleveland Clinic describes that as a classic example of sleep inertia: you hit snooze, and you may not remember deciding to. Hilditch and McHill say subjective ratings after waking can be a poor indicator of performance. If the button is the issue, see why you keep snoozing: in a 2023 survey of 1,732 people, the most common reason reported for snoozing was feeling too tired to wake up.
The Sleep Foundation says consistent wake-up times, natural light exposure, and gentle alarms can help reduce morning sleep inertia. The plain version of the wake-time part is the same wake time each day.
If the grogginess continues even when you sleep enough, talk to a GP rather than guessing at a cause. The Cleveland Clinic lists some medicines and alcohol, and some health conditions, including obstructive sleep apnoea, among things that can contribute to sleep inertia. It says to see a sleep specialist if that feeling lingers through the day and interferes with your ability to function, and that extended sleep inertia is worth a visit regardless of how much or how well you sleep. If changes are not helping, it says to see your provider. The NHS lists loud snoring, and gasping, snorting or choking noises at night, together with being tired in the day because of waking at night, as possible signs of sleep apnoea. It says not to self-diagnose, and to see a GP if you have been feeling tired for a few weeks and you are not sure why, if tiredness affects your daily life, or if you are tired and have been told you make gasping, snorting or choking noises in your sleep. The Sleep Foundation says a sleep doctor can determine whether a sleep disorder is causing more severe sleep inertia.
The next morning, look at what your phone recorded for that alarm. A snooze or dismissal means you acted on it. That fits the half-asleep snooze the Cleveland Clinic describes, where you may not remember the decision. If it rang out, the log shows no response. This is your own alarm history, not a documented phone feature, and it does not prove what you heard. What studies say about snoozing is on is snoozing bad for you.
Match the step to the check above. The sleep, wake-time, and light steps are suggestions from the sources above, for the grogginess. A backup alarm is a spare, not something a cited study has shown will stop you sleeping through the sound.
The Sleep Foundation says gentle alarms can help reduce morning sleep inertia, and that a loud, jarring alarm could worsen the confusion or grogginess on waking. The Cleveland Clinic says an alarm can be ear-splitting and still easy to ignore. This page does not claim that a louder sound has been shown to stop anyone sleeping through an alarm, and it does not name or rank alarms, clocks, or apps.
Rise won't make you hear an alarm you sleep through.
Rise is an Android alarm app with optional Pay to Snooze. iOS is coming soon.
You set a snooze price per alarm, in tokens. There is no minimum. The price is locked once the alarm rings. You can switch Pay to Snooze off for any alarm. At a zero balance, snooze falls back to free.
Snooze length is adjustable, and the default is 9 minutes.
Tokens are bought in the app, in packs: 10 for £0.89, 50 for £3.49, and 200 for £8.99. No card is charged automatically. Tokens don't expire.
How Pay to Snooze works. See also how to wake up on the first alarm and how to stop hitting snooze.
Get Rise on Google PlayNot enough sleep can make sleep inertia worse. Hilditch and McHill say prior sleep loss does that, and the Sleep Foundation says most healthy adults need between 7 and 9 hours a night. That source also says consistent wake-up times can help reduce morning sleep inertia. If it continues despite enough sleep, see a GP.
Sleep inertia is the groggy state just after waking. The Cleveland Clinic says it usually lasts 15 to 60 minutes, and longer if you are badly sleep-deprived. Its example is hitting snooze and not remembering the decision. Hilditch and McHill say subjective ratings after waking can be a poor indicator of performance.
Get more sleep. The Cleveland Clinic suggests going to bed 30 minutes earlier for a while, and the Sleep Foundation says most healthy adults need between 7 and 9 hours a night. Keep a consistent wake time, get morning sunlight, and move the alarm across the room if you snooze without realising. See a GP if the grogginess continues.
The Cleveland Clinic says to see a sleep specialist if grogginess lingers through the day and interferes with functioning, and a provider if changes are not helping. The NHS lists loud snoring with gasping, snorting or choking at night, and daytime tiredness from waking at night, as possible signs of sleep apnoea. It says not to self-diagnose.
An app can't make you hear an alarm you sleep through. Rise is an Android alarm app with optional Pay to Snooze. You set a token price per alarm, with no minimum, and that price is locked once the alarm rings. You can switch Pay to Snooze off for any alarm.
This page is general information, not medical advice.
Checked 28 October 2026.