What Is Jet Lag?

Transient Circadian Disorder Occurs in Rapid Travel Across Time Zones

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Jet lag is a circadian disorder that transiently occurs after rapid travel across multiple time zones. It may be associated with other physical symptoms, including disturbed sleep. Learn about this common condition, its symptoms, and potential treatments.

Biology of Jet Lag

If you have ever flown across a few time zones, you are undoubtedly familiar with the struggles of adjusting your sleep to the new hours. Why is jet lag, as it is called, so hard to tolerate and is there anything to be done?

Our biological clock, which is controlled by a part of the brain called the suprachiasmatic nucleus, helps us to keep a regular schedule by releasing hormones on a regular pattern. This pattern is called a circadian—or “near-day”—rhythm. Our sleep follows this same regular pattern.

Your body wishes to keep a regular sleep schedule. Our bodies like when we go to bed and get up at the same time every day. When we disrupt the regularity of these cycles, our body treats us unkindly by making us sleepy or alert when we don’t wish to be.

For example, if you were to go to bed three hours early tonight, you would have great difficulty falling asleep. However, if you fly from California to New York and crawl into bed at your normal bedtime, you are effectively attempting the same thing.

Jet Lag Symptoms

Brianna Gilmartin / Verywell

How It Develops

Rapid travel across multiple time zones leaves the circadian rhythms out of sync with the destination’s light-dark cycles. These rhythms affect sleep and wakefulness as well as metabolism, body temperature, and hormone release.

It can take time for the internal circadian rhythm to be re-synchronized to external time cues. Jet lag is sometimes called desynchronosis, referring to the misaligned sense of time.

As a general rule, it is possible to adapt at an average rate of one hour per day. For someone who lives in California to fly to New York and cross three time zones, it would usually take three days to adjust to the new time zone. It is generally easier to travel westward and harder to travel eastward for most people.

Social jet lag may cause less intense symptoms and occurs in people who delay their bedtime and wake time by one to two hours on weekends and then have to correct as the workweek resumes on Monday. This shift in the circadian timing may affect the start of the workweek for several days.


In the new location, circadian signals may conflict with environmental and social cues in the context of jet lag. This may lead to a constellation of symptoms, including:

  • Excessive daytime sleepiness
  • Fatigue
  • Insomnia
  • Irritability
  • Poor concentration
  • Digestive problems (dyspepsia)
  • Malaise (feeling unwell)

These symptoms may be disruptive and may be exacerbated by sleep deprivation, dehydration, sleep environment changes, and stress associated with travel.


The presence of the typical symptoms in the context of jet travel across multiple time zones confirms the diagnosis without the need for further testing.

In research, it is possible to measure an individual’s circadian pattern with tests that detect melatonin levels, often sampled from repeated saliva measurements. There are also new blood tests coming into clinical use that may identify an individual's circadian rhythm.

Associated Conditions

Jet lag is most commonly associated with insomnia, defined as difficulty falling asleep or returning to sleep after waking. If insomnia occurs for less than three months, it is termed acute insomnia.

As most people would be taking trips of a shorter duration than this, and the time to adjust would be more than sufficient, it would be grouped with other briefer disturbances of sleep. In some cases, jet lag may trigger a disruption that may evolve into a chronic form of insomnia.


How can you counter our circadian rhythm when you travel? There are several techniques to reduce the effects of jet lag.

One solution would be to keep the same hours as our original time zone, going to bed and getting up based on the times at home. This may not be the best way to enjoy your travels, especially if you fly great distances. An alternative would be to slowly adapt to the new time zone prior to leaving.

It may be possible to prepare the body gradually prior to departure by slowing adjusting bedtime and wake time to match the destination’s time. This can be done by adjusting your sleep by an hour for a week at a time. If you are crossing two time zones, the change can occur over two weeks.

If traveling west, you would go to bed and get up an hour later for one full week. During the second week you would repeat the same, going to bed and getting up another hour later.

If traveling east, you would go to bed and get up an hour earlier each week. If you can slowly adapt to the change, you will tolerate it better.  Unfortunately, unless the trip is quite lengthy, you wouldn’t be able to adjust the other way for your return home.

This adjustment may be enhanced with properly time light exposure. Light is one of the primary synchronizers of the circadian rhythm in sighted individuals.

It may advance the timing of sleep earlier if the light exposure occurs in the two hours prior to the normal wake time or immediately upon awakening. Sunlight is best, but the use of light boxes or light therapy glasses may also have a role.

Beyond light, it may be important to address the symptoms that occur. Caffeine or strategic napping may relieve sleepiness. Other stimulant medications could also have a role. It may also be helpful to use hypnotic medications to aid sleep, including over-the-counter melatonin.

There may also be a role for prescription pills, such as:

These medications to aid both wakefulness and sleep may ease the transition to a new time zone.

A Word From Verywell

If you have a big trip coming up, you might plan ahead in how you can adjust your circadian pattern of sleep and wakefulness with some of the interventions outlined. This may help to optimize your experience while traveling and ensure that you avoid the symptoms of jet lag.

5 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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By Brandon Peters, MD
Brandon Peters, MD, is a board-certified neurologist and sleep medicine specialist.