Sleep needs vary from person to person. Age, genetics, lifestyle, and environment all play a role.
According to the National Sleep Foundation, adults need 7-9 hours of sleep a night. People who sleep seven hours a night are healthier and live longer. While the guideline is helpful, you are the best person to judge how much sleep you need.

How much sleep is enough

Health

If you often feel tired, your body is telling you that it's not getting enough sleep.
If you're getting eight hours of sleep a night but still feel tired, you may be suffering from a sleep disorder or interrupted sleep.

Ask yourself: 'Am I seepy?'

A sleep diary will give you important insights into your sleep habits.
For one week, write down:
<ul>
<li>The time you go to bed and the time you wake up.</li>
<li>The number of hours you sleep and whether you took naps or woke up during the night.</li>
<li>Notice how you feel in the morning—refreshed or fatigued?</li>
</ul>

Keep a sleep diary

To really find out what your individual sleep needs are, do the following experiment for at least two weeks:
<ul>
<li>Pick the same bedtime every night.</li>
<li>Turn off your alarm.</li>
<li>Record the time you wake up.</li>
</ul>
You may sleep longer during the first few days, but over the course of a few weeks, a pattern will emerge of how much sleep your body needs each night.

Take a vacation from your alarm clock

Most people know they need to eat right and exercise to be healthy. But what about sleep? We spend about one-third of our lives asleep, and sleep is essential to better health. But many of us are struggling with sleep. Four out of five people say that they suffer from sleep problems at least once a week and wake up feeling exhausted. So how do you become a more successful sleeper? Grab a pillow, curl up and keep reading to find out.

By <a dir="ltr" href="https://www.twitter.com/nytimeswell" rel="noreferrer noopener">Tara Parker-Pope </a>

Illustrations by Sam Kalda

Most people know they need to eat right and exercise to be healthy. But what about sleep? We spend about one-third of our lives asleep, and sleep is essential to better health. But many of us are struggling with sleep. Four out of five people say that they suffer from sleep problems at least once a week and wake up feeling exhausted. So how do you become a more successful sleeper? Grab a pillow, curl up and keep reading to find out.

If you wake up tired, chances are you’re not getting enough sleep. These strategies may help you determine your sleep needs.

The best person to determine how much sleep you need is you. If you feel tired, you probably need more sleep. But science does offer some more specific guidance. People who sleep seven hours a night are healthier and live longer. Sleeping less than seven hours is associated with a range of health problems including obesity, heart disease, depression and impaired immune function. But sleep needs vary greatly by individual. Age, genetics, lifestyle and environment all play a role. The National Sleep Foundation recently updated its sleep recommendations based on age.

While these numbers are useful guidelines, they really don’t tell you anything about your individual sleep needs, which are largely determined by genetics — and strongly influenced by your habits.

This simple question is the best way to determine if you’re getting adequate sleep. If you often feel tired at work, long for a nap or fall asleep on your morning or evening commute, your body is telling you that it’s not getting enough sleep. If you’re getting seven or eight hours of sleep a night but still feeling tired and sleep-deprived, you may be suffering from interrupted sleep or a sleep disorder and may need to talk to a doctor and undergo a sleep study.

Even if you think you’re getting enough sleep, you may be surprised once you see your sleep patterns in black and white. Some of the new activity trackers will monitor your sleep patterns for you, but you can also do it easily yourself. For the next week, keep a sleep diary:

1. Write down the time you go to bed and the hour you wake up.

2. Determine the total number of hours you sleep. Note whether you took naps or woke up in the middle of the night.

3. Note how you felt in the morning. Refreshed and ready to conquer the world? Or groggy and fatigued?

Not only will a sleep diary will give you important insights into your sleep habits, but it will be useful to your doctor if you think you are suffering from a sleep disorder.

Want to really identify your individual sleep needs? Try this “sleep vacation” experiment. To do this, you will need two weeks when you don’t have somewhere to be at a specific time in the morning. If you have a flexible job, you can do this any time, or you may have to wait until a vacation.

The experiment requires a little discipline:

1. Pick the same bedtime every night.

Chances are, you will sleep longer during the first few days, because you are catching up on lost sleep, so the first few days of data won’t be useful. But over the course of a few weeks, if you stick to the scheduled bedtime and allow yourself to wake up naturally, you’ll begin to see a pattern emerge of how many hours of sleep your body needs each night.

Once you determine your natural sleep needs, think about the time you need to wake up to get to work or school on time and pick a bedtime that allows you enough sleep to wake up naturally.

Do you pop out of bed bright and early, ready to take on the world? Or do you find yourself making friends with the snooze button after staying up all night?

Do you wake up hungry? What’s your best time of day? Those and other questions are part of a test commonly used by sleep experts to determine whether you are a lark, a night owl or somewhere in between.

You can <a dir="ltr" href="http://well.blogs.nytimes.com/2012/05/03/the-well-quiz-are-you-a-morning-person/"><ins dir="ltr">take this quiz </ins> </a>to find out what type of person you are.

Like most creatures on Earth, humans come equipped with a circadian clock, a roughly 24-hour internal timer that keeps our sleep patterns in sync with our planet — at least until genetics, age and our personal habits get in the way. Even though the average adult needs eight hours of sleep per night, there are so-called “shortsleepers,” who need far less, and morning people, who, research shows, often come from families of other morning people. Then there’s the rest of us, who rely on alarm clocks.

For those who fantasize about greeting the dawn with a smile, there is hope. With a little focus, discipline and patience, you have the ability to reset your own internal clock. But be warned, it’s not easy. Changing your sleep pattern requires commitment, and it means changing old habits. No more TV-watching marathons late into the night.

Changing your internal sleep clock requires inducing a sort of jet lag without leaving your time zone, and sticking it out until your body clock resets itself. And, most importantly, not resetting it again.Here’s how to become more of a morning person.

Step 1: Set a goal for your wake-up time.

Step 2: Move your current wake-up time by 20 minutes each day. For example, if you regularly rise at 8 a.m., but really want to get moving at 6 a.m., set the alarm for 7:40 a.m. on Monday. On Tuesday, set it for 7:20 a.m. and so on until you are setting your alarm for 6 a.m.

Step 3: Go to bed when you are tired. Avoid extra light exposure from computers or televisions as you near bedtime.

Step 4: When your alarm goes off in the morning, don’t linger in bed. Hit yourself with light — open your shades, turn on the lamp.

Step 5: Go to bed a little earlier the next night. In theory, you should get sleepy about 20 minutes earlier each night.

A word of warning: While this method works for many, it doesn’t work for everyone. Very early risers and longtime night owls have a hard time ever changing.

If you are struggling to wake up in the morning, sleep experts suggest a few simple ways to train your body.

Buy a Louder Alarm: It may sound silly, but if you regularly sleep through your alarm, you may need a different alarm. If you use your phone alarm, change up the ring tone and set the volume on high.

Sunlight: One of the most powerful cues to wake up the brain is sunlight. Leaving your blinds open so the sun shines in will help you wake up sooner if you regularly sleep late into the day.

Eat Breakfast: Eating breakfast every day will train your body to expect it and help get you in sync with the morning. If you’ve ever flown across time zones, you’ll notice that airlines often serve scrambled eggs and other breakfast foods to help passengers adjust to the new time zone.

Don’t Blow It on the Weekend: Besides computer screens, the biggest saboteur for an aspiring morning person is the weekend. Staying up later on Friday or sleeping in on Saturday sends the brain an entirely new set of scheduling priorities, so by Monday, a 6 a.m. alarm may feel like 4 a.m. It’s tough, but stick to your good sleep habits, even on the weekends.

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Tired people are not happy, healthy or safe. Here are some of the things that go wrong when you don’t get enough sleep.

People who get less than seven hours of sleep a night are more likely to have chronic health problems like obesity, heart disease, diabetes, high blood pressure, stroke, depression and premature death.

While the long-term health risks of bad sleep are enough to keep you awake at night, there’s more bad news. You’re also <a dir="ltr" href="http://well.blogs.nytimes.com/2015/09/02/short-sleepers-may-catch-more-colds/?_r=0"><ins dir="ltr">more likely to catch a cold. </ins> </a>In one surprising study, researchers found 164 men and women who were willing to take nose drops that exposed them to the cold virus. (And that’s not the most surprising part of the story.) You might think that everyone who willingly puts a cold virus in their nose would get sick, but they don’t. A healthy immune system can fight off a cold. But not a sleep-deprived immune system. The people most likely to get sick from the cold-infused nose drops? Those who got six or fewer hours of sleep.

A tired brain is not a wise brain, and people who are sleep deprived make more mistakes. <a dir="ltr" href="http://jamanetwork.com/journals/jamapsychiatry/fullarticle/1370486"><ins dir="ltr">The American Insomnia Survey, </ins> </a>published in 2012, estimated that 274,000 workplace accidents were directly related to sleep problems. The bill for these sleep-deprived mistakes? $31 billion annually.

Why does this happen? While the body goes into rest mode during sleep, the brain becomes highly active. Think of your brain like a computer or a smartphone that uses the nighttime to back up all your data. One of its big jobs is to consolidate memories, link with old memories and create paths for you to retrieve memories. It also forms connections between disparate thoughts and ideas. That’s why sometimes, when you wake up, a big idea suddenly pops into your head. And it’s why, when you don’t sleep, your thinking and memory are fuzzy. <a dir="ltr" href="https://newsinhealth.nih.gov/issue/apr2013/feature2"><ins dir="ltr">Some research suggests </ins> </a>that when you don’t sleep (like when students pull an all-nighter), your ability to learn new information drops by almost half.

Another important function of sleep is that it allows the brain to do some mental housekeeping. Yes, sleep helps you clean up the cerebellum, polish the parietal and flush the frontal lobe. Sleep cleans out the toxic junk in your brain. <a dir="ltr" href="http://www.nytimes.com/2014/01/12/opinion/sunday/goodnight-sleep-clean.html?_r=0">In mouse studies, </a>researchers found that during sleep, the space between brain cells gets bigger, allowing the brain to flush out toxins. While more study is needed, the research suggests that not sleeping can allow toxins to accumulate and may be linked with brain diseases like Parkinson’s and Alzheimer’s.

<a dir="ltr" href="http://well.blogs.nytimes.com/2013/01/04/drowsy-drivers-pose-major-risks/"><ins dir="ltr">Drowsy driving is as much of a safety risk as drunk driving or texting and driving. </ins> </a>Studies show that going without sleep for 20 to 21 hours and then getting behind the wheel is comparable to having a blood alcohol level of about .08 percent, the legal limit in most states. If you’re awake for 24 hours and then try to drive, you’re at a blood alcohol equivalent of 0.1 percent, which is higher than the legal limit in all states.

You are at risk for drowsy driving if you get less than six hours of sleep at night. Another risk factor is snoring. Snorers also are at risk for drowsy driving because snoring is a sign of sleep apnea and interrupted sleep. (See our section below, “Call a Doctor,” for more on sleep apnea.)

In 2009, an estimated 730 deadly motor vehicle accidents involved a driver who was either sleepy or dozing off, and an additional 30,000 crashes that were nonfatal involved a drowsy driver. Accidents involving sleepy drivers are more likely to be deadly or cause injuries, in part because people who fall asleep at the wheel either fail to hit their brakes or veer off the road before crashing.

Groggy drivers often blast the radio or roll down the window to stay awake, but those measures don’t really work, say experts. Coffee or a caffeinated drink may help, but some individuals don’t get much of an effect. The best advice if you find yourself sleepy at the wheel: Pull over for a quick cat nap.

For years researchers have known that <a dir="ltr" href="http://aje.oxfordjournals.org/content/164/10/947.full"><ins dir="ltr">adults who sleep less than five or six hours a night are at higher risk of being overweight </ins> </a>. Among children, sleeping less than 10 hours a night is <a dir="ltr" href="http://www.hsph.harvard.edu/obesity-prevention-source/obesity-causes/sleep-and-obesity/"><ins dir="ltr">associated with weight gain </ins> </a>. Some research even shows that losing just a few hours of sleep a few nights in a row can lead to almost immediate weight gain.

Part of the reason may be that sleep-deprived people eat more. Staying up late and skimping on sleep leads to more eating in general, and a hankering for carbohydrates. In one study, sleep-deprived eaters ended up eating more calories during after-dinner snacking than in any other meal during the day. By the end of the first week the sleep-deprived subjects had gained an average of about two pounds. Over all, people consumed 6 percent more calories when they got too little sleep. Once they started sleeping more, they began eating more healthfully, consuming fewer carbohydrates and fats.

The first step toward better sleep is better “sleep hygiene” – daily habits that train your body for sleep.

Like most creatures on earth, humans come equipped with a circadian clock, a roughly 24-hour internal timer that keeps our sleep patterns in sync with our planet. At least until our personal habits get in the way.Here are the key factors that matter for your “sleep hygiene”:

Bedtime: Go to bed at about the same time every night, including weekends.

Don’t Sleep In: Keep your wake-up time consistent. Don’t sleep in on the weekends.

Naps: Avoid naps. If you must take a nap, set the alarm so you don’t sleep for more than an hour. Don’t take a nap after 3 p.m.

Keep to a Schedule: Schedules aren’t just about bedtime and wake-up time. It also means eating your meals, taking medications, exercise and even watching television should occur about the same time every day to keep your body clock in sync.

Avoid Screens: Turn off the tablet, the television and the phone. The blue light in your screen has the same effect on your brain as sunlight, which means it wakes you up just when you want to be drifting off.

Think Spa Bedroom: Make your bedroom a pleasant, peaceful and relaxing getaway. Get rid of exercise equipment, televisions, small children, etc.

Beds Are for Sleep and Romance: Don’t use the bed for watching television, talking on the phone, doing homework or eating and drinking.

Work Out Early: Strenuous exercise is not a good idea right before bedtime. Try yoga.

No Night Eating: Don’t eat meals close to bedtime and avoid evening and late night snacking. If your body is churning through a big meal, it’s certainly not going to get the rest it needs. And if you’re overweight or prone to digestion problems, you’re likely to experience painful heartburn and reflux if you binge too close to bedtime.

Catch Some Morning Rays: Sunlight keeps your internal clock ticking. Go outside as soon as you wake up and spend at least 15 minutes in the morning sun. (And if it’s a hot sun, use sunscreen.)

Keep It Cool: Cool bodies sleep better, but most people keep their bedrooms too warm at night, which can interfere with sleep. Taking a hot bath before bedtime is a good idea, because once you get out of the bath, your body cools down more quickly, which will help you drift off to sleep.

If you have adopted better sleeping habits and you are still suffering from chronic sleepiness, you may need to see a doctor.

More than 40 million Americans suffer from chronic, long-term sleep disorders, and an additional 20 million report sleeping problems occasionally, according to the National Institutes of Health. Here are some of the medical reasons people are losing sleep at night.

Insomnia: If you regularly have trouble with falling asleep, staying asleep or waking too early, you suffer from insomnia. Treatment includes behavioral therapy, strict sleep hygiene and medication.

Sleep Apnea: If you suffer from excessive daytime sleepiness, the cause may be sleep apnea. A person typically doesn’t know he or she has sleep apnea, and is usually alerted to the problem by a bed partner who must cope with the loud snoring, snorts and gasps that are often associated with the disorder. A person with sleep apnea experiences pauses in breathing while sleeping. These pauses can last for seconds to minutes and occur dozens of times in an hour. Breathing restarts with a gasp, a choking sound or a snort. When this occurs, a person may not wake up, but he or she moves from deep sleep to light sleep, and wakes feeling tired and fatigued.Sleep apnea is unpleasant for a bed partner, and it’s risky to your health. If you think you have it, see a doctor.

Restless Legs Syndrome: An estimated 8 percent of the population has restless legs syndrome, a neurological condition. There are four basic symptoms that occur with R.L.S.:

1. A strong urge to move your legs, sometimes accompanied by a burning sensation.

2. Your symptoms are worse when you body is at rest.

3. Symptoms improve when you move.

Anxiety: Anxiety can interfere with sleep. And feeling sleep-deprived can cause anxiety. Most psychiatric disorders are linked with some type of sleep problem. And people with chronic insomnia are at risk for anxiety disorders.

Bite‑sized knowledge
to upgrade
your career

How to Get a Better Night's Sleep - Well Guides

How much sleep is enough

Ask yourself: 'Am I seepy?'

Keep a sleep diary

Take a vacation from your alarm clock

Rise and Shine! Sleep Better and Wake Up at the Same Time Every Day

How to Sleep Better

Waking Up Tired: Exercise, Sleep Environment, Aging, Other Causes

Bite‑sized knowledgeto upgradeyour career

How to Get a Better Night's Sleep - Well Guides

How much sleep is enough

Ask yourself: 'Am I seepy?'

Keep a sleep diary

Take a vacation from your alarm clock

Rise and Shine! Sleep Better and Wake Up at the Same Time Every Day

How to Sleep Better

Waking Up Tired: Exercise, Sleep Environment, Aging, Other Causes

Bite‑sized knowledge
to upgrade
your career