Snooze University

How Do You Know if You Are Sleep Deprived?

by Dale Cudmore | Updated: Jun 01, 2023

This is one of those questions where the answer is, “if you have to ask, you probably are.”

Most people are sleep deprived, even without knowing it. Although to different degrees.

I’m going to quickly go over the relevant research on sleep deprivation, how you can tell if you are sleep deprived, and how much sleep you actually need.

How Fast Can You Become Sleep Deprived?

One night.

Just one night of getting a bit less sleep than you need will have significant effects on your attention, alertness, and coordination (1):

Nocturnal sleep periods reduced by as little as 1.3 to 1.5 hours for 1 night result in reduction of daytime alertness by as much as 32%

These changes typically aren’t obvious to us, but if you measure your alertness using a test, you would see a difference.

But most people don’t get enough sleep on a regular basis, and become chronically sleep deprived. You can get a good idea if you are chronically sleep deprived with this quick sleep deprivation test.

Fatigue is a major factor in 10% of fatal car accidents (2). If you have a dangerous job, or a job in healthcare, being well rested is even more important.

SummaryEven one night of not getting enough sleep can leave you sleep deprived with significant side effects. Chronic sleep deprivation can lead to serious consequences.

Sleep Quality Matters Too

The other factor that most people don’t consider is sleep quality.

If you get 8 hours of sleep, but you’re tossing and turning and waking up frequently, you’re not going to be well rested.

To measure your sleep quality, use this Pittsburgh Sleep Quality Index Online Calculator.

If you have a global score of 5 or under, your sleep quality is excellent.

If it’s above 5, you may want to try not only improving the amount of sleep you get, but also the quality of your sleep. You can start by improving your sleep hygiene.

How Much Sleep Do You Need?

Just under 30% of young adults get 6.5 hours or less of sleep on weeknights (1). That’s obviously not enough.

But it’s not always so clear.

In order to tell if you’re sleep deprived, you need to determine how much sleep you actually need.

This is a tough thing to do.

The way most research studies approach this is to :

  1. Set up a good sleep environment (dark, quiet, etc.).
  2. Give sleepers as much time as they’d like to sleep for an extended period (for at least 2 weeks usually).
  3. The average amount near the end is how much they probably ideally need.

You want to ignore the sleep in the first few days or week because that’s usually “catching up” on sleep debt.

For example, one study looked at 15 people (3) and found:

This implies that the actual sleep need for these 7.2-hour sleepers was about 8.5 hours.

Losing over an hour of sleep per night will result in chronic sleep deprivation.

Ideally, this is a sort of test you could do yourself on a vacation.

If that’s not possible, make a spreadsheet and record how long you sleep each night, as well as how well you score on an online test. There are free tests for alertness online that you can use for this (Here’s one example).

SummaryOver time, you’ll find that alertness improves with more sleep up until a certain point, and that’s the amount of sleep you should aim for.

How Serious is Sleep Deprivation

Sleep impacts almost every part of our health. It's important to correct sleep deprivation either by yourself or with the help of a doctor.

If someone is sleep deprived regularly, it can lead to:


  1. We are Chronically Sleep Deprived
  2. Fatal Accidents among Car and Truck Drivers: Effects of Fatigue, Age, and Alcohol Consumption
  3. Conservation of photoperiod-responsive mechanisms in humans

Medical Disclaimer: The information on is not intended to be a substitute for physician or other qualified care. We simply aim to inform people struggling with sleep issues about the nature of their condition and/or prescribed treatment.

About the authorDale is the founder of Snooze University and a sleep researcher. I overcame my sleep issues and now I'd like to help you do the same by summarizing the latest sleep studies for you.