Health Information and Tools >  Sleep and Your Body Clock

Main Content

Sleep and Your Body Clock


The body's "biological clock," or 24-hour cycle (circadian rhythms), controls functions such as sleeping and waking. Your body clock can be affected by light or darkness. They can make the body think that it's time to sleep or wake up.

Health Tools

Health Tools help you make wise health decisions or take action to improve your health.

Actionsets are designed to help people take an active role in managing a health condition.

Sleep Problems Related to Your Body Clock

Your body's biological clock (circadian rhythms) affects your sleep-wake cycle, your body temperature, and other important body functions. Body clock sleep problems have been linked to a hormone called melatonin. This hormone helps you fall asleep and stay asleep. Light and dark affect how your body makes melatonin. Most melatonin is made at night. During the day, light tells your body to make less melatonin. If you work at night in artificial light, your body may be making less melatonin than it needs.

Things that may affect your body clock and can cause sleep problems include:

Jet lag.

Crossing time zones disrupts your body clock. You have sleep problems because your body clock has not adjusted to the new time zone. Your body thinks that you're still in your old time zone. For example, if you fly from Winnipeg to Rome, you cross seven time zones. This means that Rome is 7 hours ahead of Winnipeg. When you land in Rome at 6:00 in the morning, your body thinks it's still in Winnipeg at 11:00 the previous night. Your body wants to sleep, but in Rome the day is just starting.

Changes to your sleep schedule.

When you work at night and sleep during the day, your body's internal clock needs to reset itself. Sometimes that's hard to do. People who work the night shift or rotate shifts may have trouble sleeping during the day and may feel tired at night when they need to be alert for work.

Your sleep environment.

Too much light or noise can make your body feel like it's not time to sleep.


Certain illnesses and health problems can affect sleep patterns. These include dementia, a head injury, recovering from a coma, and severe depression. Some medicines that affect the central nervous system may also affect sleep patterns.

Drugs and alcohol.

Some drugs cause sleep problems. And, although you may fall asleep with no problems after drinking alcohol late in the evening, drinking alcohol before bed can wake you up later in the night.

Being a "night owl."

Night owls have a hard time falling asleep until very late at night or very early in the morning. These sleep patterns may or may not cause problems. It depends on each person's lifestyle and work or school schedule. If night owls don't get enough sleep, they can feel tired and need to sleep during the day.

Being an "early bird."

Early birds fall asleep early—at 8 p.m. or earlier—and wake up early—between 3 a.m. and 5 a.m. These sleep patterns may or may not cause problems. It depends on each person's lifestyle and work or school schedule.

Learn more


Managing Jet Lag

Jet lag is a sleep problem that happens when you fly across two or more time zones. The more time zones you cross, the worse it may be. Symptoms include not sleeping well, feeling sleepy during the day, and being constipated. Most people get better 3 to 4 days after their flight.

You may be able to prevent or reduce the symptoms of jet lag. Here are some things you might try.

  • Try melatonin.

    Melatonin is a hormone that your body makes. It regulates the cycle of sleeping and waking. Taking a melatonin supplement may help "reset" your biological clock.

    Your doctor can recommend how much to take and when to take it. Your doctor may suggest that you:

    • Take melatonin after dark on the day you travel and after dark for a few days after you arrive at your destination.
    • Take melatonin in the evening for a few days before you fly.
  • Prepare for jet lag before you go and on the plane.

    Take these steps. They have not been proved to reduce jet lag, but some people find them helpful.

    • If you have an important event, try to arrive a few days early so your body can adjust to the new time zone.
    • Be well rested before you start to travel.
    • If you are flying east, go to bed 1 hour earlier each night for a few days before your trip. If you're flying west, go to bed 1 hour later each night instead. But if your trip will last 2 days or less, you may choose to stay on your home time.
    • Set your watch to your new time zone as you start flying. If it's nighttime at your destination, try to sleep on the plane. Sleep masks, earplugs, and headphones may help. If it's daytime at your destination, try to stay awake.
    • On the plane, drink water to avoid dehydration. Avoid alcohol and drinks that contain caffeine.
  • Help yourself adjust once you arrive.

    Take these steps. They have not been proved to reduce jet lag, but some people find them helpful.

    • Try to change your schedule to the new time as soon as you can. For example, if you arrive at 4 p.m., do your best to stay awake until your usual bedtime. Get up in the morning instead of sleeping late.
    • Think about light exposure. If you flew east, try to avoid bright light in the morning, and get light in the afternoon. To avoid light in the morning, stay indoors, such as by going to a mall or a museum. If you flew west, stay awake during daylight, and try to sleep after dark. This may help adjust your body clock and help your body make melatonin at the right time.
    • Caffeine may help you stay alert during the day after you arrive. But it also may make it harder to sleep at night.
  • Ask your doctor about prescription sleeping medicine.

    A medicine may help you sleep after you arrive at your destination.

Learn more

Self-Care When Working Nights or Shifts

When you work nights or rotating shifts, taking good care of yourself can be a challenge.

It's common to feel "off," tired, or disconnected from the rest of the world. And that can make it hard to get in a good, healthy routine.

The following tips may help you make some changes. Your doctor may recommend things for you to try. You can choose the ones that you feel ready to try.

  • Get good sleep.

    It can be tough to get good, restful sleep during the day. Our bodies often prefer to sleep at night. To help your body prepare for sleeping during the day, you can:

    • Wear dark glasses on your way home from work. This helps send a message to your body that it's almost time to sleep.
    • Avoid caffeine drinks for at least 6 hours before you go to sleep.
    • Keep your bedroom quiet, dark, and cool. Use curtains, blinds, or a sleep mask to block out light. Cover clocks in your bedroom with a towel. To block out noise, try earplugs, soothing music, or a "white noise" machine.
    • Try to not use technology such as TVs, smartphones, computers, or tablet devices for at least an hour before you go to sleep.
    • Do something to relax before you go to bed. You might try a warm shower or bath or maybe some deep breathing or stretching.
  • Keep the same sleep and wake times.

    This includes the days you don't work.

  • Take care of your body.

    It may be hard to keep up your regular exercise routine. But you can try to get some extra activity at work.

    • Take a walk during your breaks. If you work at a desk, do stretches in front of your computer.
    • Use your commute to do some extra walking. Park several blocks away, or get off the bus a few stops early.
    • Use the stairs instead of the elevator.

    Try to eat meals, at regular times. Eating at set times is important for your body.

    Be aware that not getting enough sleep can often make you feel hungry. If you feel hungry:

    • Ask yourself: "Am I hungry enough to eat an apple?" If you're not hungry enough for an apple, then your body may not be truly hungry.
    • Drink some water. Dehydration can feel like hunger. And that means drinking more water can make you feel less hungry.

    Take your medicines safely.

    • Changes in your schedule can make it harder to remember to take any prescription medicines you need to take. Try setting an alert on your phone, using a paper calendar, or using a pill box.
    • Keep a supply of medicines at work, if you'll need them there.
  • Make rotating shifts easier.

    If your shift times tend to change a lot, you can:

    • Talk to your manager about keeping shift changes to a minimum, if possible.
    • Try to have shifts rotate clockwise. For example, it's better to rotate from a day shift, to an evening shift, to a night shift. This is easier for your body to adjust to than random shift changes.
  • Stay connected to your loved ones.

    It can be hard to miss important events or to have to sleep when everyone else is awake. To help stay connected to the people you love:

    • Make a calendar the whole family can see. Include your work hours and your sleep hours. This will help everyone know when they can expect to see you.
    • Plan a weekly activity that you can all look forward to. Make a plan to call your kids or your partner on scheduled breaks.

Learn more

Adjusting Your Body Clock

Night owls

Some people, no matter what they do, have trouble falling asleep at night and being up early during the day. They are often called "night owls." Their sleep patterns may or may not cause problems for them. It depends on their lifestyle and work or school schedule. If you are a night owl but want to change your sleep schedule, there are things you can try so that you fall asleep earlier and sleep through the night.

  • Have healthy sleep habits.

    Examples of healthy habits include:

    • Get up at the same time each day.
    • Avoid alcohol and drinks with caffeine before bed.
    • Do not smoke or use other types of tobacco near bedtime.
    • Do not nap during the day.
    • Do not read, watch TV, or use your phone in bed.
  • Ask your doctor about taking melatonin.

    You might take melatonin supplements in the evening to help you get to sleep. Your doctor can recommend how much to take and when to take it.

  • Try using light therapy.

    Light therapy means exposing yourself to bright light as soon as you wake up. You can use a bright (10,000 lux) light or a full-spectrum light box for 30 to 45 minutes each day. Ask your doctor for a specific schedule for when to use the light.

  • Try moving your bedtime slowly over time.

    Gradually move your bedtime earlier and earlier. Your body may get used to the change in schedule.

Early birds

People who fall asleep very early and wake up before dawn are often called "early birds." If you are an early bird but want to change your sleep schedule, there are things you can try so that you can stay up later at night and sleep later in the morning.

  • Use light therapy.

    In this case, light therapy means exposing yourself to bright light in the evening. Use a bright (10,000 lux) light box or a full-spectrum light box for 30 to 45 minutes each day.

  • Try moving your bedtime slowly over time.

    Gradually move your bedtime later and later. Your body may get used to the change in schedule, and you may sleep later in the morning too.

Learn more


Current as of: July 11, 2023

Author: Healthwise Staff
Clinical Review Board
All Healthwise education is reviewed by a team that includes physicians, nurses, advanced practitioners, registered dieticians, and other healthcare professionals.

This information does not replace the advice of a doctor. Healthwise, Incorporated, disclaims any warranty or liability for your use of this information. Your use of this information means that you agree to the Terms of Use. Learn how we develop our content.