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Jet lag

Medically reviewed by Last updated on Jul 6, 2023.

What is Jet lag?

Harvard Health Publishing

Jet lag is a type of sleep disorder that is a reaction to traveling between time zones.

Our bodies naturally develop a sleep-wake cycle that is tied to the patterns of light and dark in our environment. This cycle, called the circadian rhythm, affects many body processes, including temperature and hormone levels.

Because traveling between time zones changes the light-dark patterns in your environment, it can disrupt your body's rhythms. A change of even a few hours may not seem significant, but often it is enough to affect the body's sleep-wake cycle. For example, a Californian who travels to New York may receive a wake-up call at 7 a.m., but his or her body still is running on California time, where it is only 4 a.m.

The effects of jet lag go beyond being tired for a few extra hours. Because the disruption in the sleep-wake cycle affects your body's hormone levels, many body processes can be thrown off balance, leading to a variety of symptoms.


Symptoms of jet lag can be mild or severe, depending on the number of time zones you cross and your sensitivity to such changes. The more time zones you cross, the more likely it is that your body rhythms will be disrupted, which can lead to more severe symptoms. Most people who cross five or more time zones will experience at least some symptoms, which can include


There are no tests for jet lag, although the cause usually is obvious. If you have typical symptoms, you do not need to seek medical attention.

If you have symptoms of jet lag lasting longer than two weeks, it is possible that something else is triggering your sleep difficulty. Your doctor may suggest an evaluation to check for other disorders.

Expected duration

For each time zone crossed during travel, it takes about a day to adjust to the new environment. For example, it can take up to three days for a person traveling from California to New York to feel "normal" again. If that person travels back to California after adjusting to New York time, it can take another three days to readjust to California time.

Older people seem to be hit harder by jet lag and may require a little more time to adjust. Traveling from west to east can cause more bothersome symptoms because the body has more difficulty adjusting its clock forward than backward.


Although nothing will prevent jet lag completely, travelers can do a few things to limit its effects:


Some people believe that the hormone melatonin helps to decrease jet lag. This hormone, which can be purchased over the counter as a supplement, is taken about 30 minutes before bed on the day of travel and for up to four days after arrival, usually at a dose of about 3 milligrams. Smaller doses (1 milligram) also may work, and some people need higher doses, about 5 milligrams.

Melatonin generally does not cause serious side effects, although there is little information on its long-term safety. Possible short-term side effects include daytime sleepiness, dizziness, headache, disorientation, loss of appetite, and nausea. Melatonin is considered a nutritional supplement, and therefore it is not closely regulated.

Prescription medications, such as benzodiazepines, may help decrease jet lag. This is particularly true for people who have difficulty falling asleep after traveling to a very different time zone.

Treatment options

The following list of medications are in some way related to or used in the treatment of this condition.

When to call a professional

Usually, it is not necessary to call a doctor to treat jet lag. However, you should call a health care professional if symptoms have not cleared up within two weeks.


Jet lag is a mild problem that goes away on its own within several days. People with regular routines and older people may have less ability to tolerate shifts in their light-dark cycles and may take slightly longer to recover. However, even for these people, all symptoms should disappear within two weeks.

Additional info

International Society of Travel Medicine

Learn more about Jet lag

Treatment options

Further information

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.