Quick Answer: Jet lag is a sleep disorder caused by fast travel across time zones. The CDC says westward travel is easier, with adaptation of about 1.5 hours a day, versus 1 hour a day going east. To prepare, shift your sleep 1 hour a day for 2 to 3 days, get morning light after an eastward trip, and keep naps to 20 to 30 minutes.
Check your body clock first with our circadian rhythm calculator.
What Is Jet Lag?
Jet lag is a sleep disorder caused by rapid travel across time zones. It creates a temporary mismatch between your internal body clock and the local time. The CDC Yellow Book says it is not just a general feeling of low energy. It can show up as sleep disturbances, cognitive impairment, daytime sleepiness, general malaise and stomach or bowel problems (CDC Yellow Book).
It is common. The chapter cites one survey in which 68 percent of international business travelers had negative symptoms on a regular basis.
What Are The Signs You Have Jet Lag?
MedlinePlus lists trouble falling asleep or waking up, and tiredness during the day (MedlinePlus). The CDC’s diagnostic criteria add two clues. Jet lag disorder involves insomnia or excessive daytime sleepiness with less total sleep after travel across at least two time zones. It also brings impaired daytime function, malaise or stomach trouble within 1 to 2 days of travel.
- You cannot fall asleep at the local bedtime.
- You are sleepy in the middle of the local day.
- Your thinking feels foggy. Cognitive impairment is one listed symptom.
- You feel generally unwell. Malaise is a listed symptom.
- Your stomach is upset. Gastrointestinal disturbance is a listed symptom.
The criteria also say the sleep problem should not be better explained by another sleep disorder, medical condition, mental disorder, medicine or substance use. If symptoms seem out of proportion to your trip, ask a clinician.
Why Is Flying East Harder?
Your body clock runs a little longer than 24 hours, so it is easier to stay up later than to go to bed earlier. The CDC explains that westward travel is easier to adapt to than eastward travel. The average rate of adaptation is 1.5 hours a day westward and 1 hour a day eastward. MedlinePlus puts it simply: traveling east can be harder because you lose time. For the basics of the clock itself, see circadian rhythm explained.
| Direction | What Your Clock Must Do | Average Adaptation |
|---|---|---|
| West | Delay the body clock (later) | About 1.5 hours a day |
| East | Advance the body clock (earlier) | About 1 hour a day |
A rough example: a 6-hour eastward shift could take about 6 days at 1 hour a day. That is simple arithmetic from the CDC rate, not a rule, and individual results vary. Risk factors named by the CDC include the number of time zones crossed, time cues at your destination, genetic differences and medicines you take.
How Can You Prepare Before You Fly?
The CDC suggests shifting your sleep toward the destination before you go. Moving sleep 1 hour later for westward travel, or 1 hour earlier for eastward travel, each day for the 2 to 3 days before the trip may reduce the time needed to adjust. MedlinePlus agrees for eastward trips: consider going to bed earlier for a couple of nights before leaving, which helps reset your internal clock.
The AASM practice parameters list the combination of morning bright light and shifting the sleep schedule 1 hour earlier each day as an option for eastward travel (AASM practice parameters). The CDC also advises choosing a flight that arrives at a time that gives you useful light exposure.
What Should You Do On The Plane?
The CDC lists these in-flight steps:
- Time meals, sleep and light exposure to the destination time zone.
- Stay hydrated, because volume depletion can worsen jet lag symptoms.
- Avoid excess alcohol. The CDC notes alcohol tends to shorten the time to fall asleep but increase sleep fragmentation.
- Limit caffeine, since both caffeine and alcohol can cause dehydration.
- Avoid sedative medicines with long half-lives.
MedlinePlus adds that during stopovers you should make yourself comfortable and get some rest.
How Does Light Help You Adjust?
Light is the main signal for your body clock. The CDC says bright light in the morning, after your body’s lowest point, promotes a shift earlier. Light in the evening tends to shift you later. The best timing depends on the direction of travel and the number of time zones, so plan it by trip.
After you land, maximize natural light at the destination, as the CDC advises. MedlinePlus says the same in simpler terms: once you arrive, spend time in the sun. Keep that in mind in the evening, when bright light can push your clock later, so dim the lights before your new bedtime.
Should You Nap After A Long Flight?
Yes, briefly. The CDC says short daytime naps of 20 to 30 minutes can help sustain alertness during the local day, while longer naps may interfere with sleep that night. Staying awake through the local day also builds the drive to sleep at night. Read 20-minute versus 90-minute nap to choose a length.
Does Melatonin Help Jet Lag?
It can, when timed correctly. The AASM practice parameters rate melatonin at the appropriate time as indicated to reduce jet lag symptoms. The CDC cautions that taking it at the wrong time can increase misalignment, and that it is less effective when your own melatonin is already high.
| Source | Dose Guidance |
|---|---|
| CDC Yellow Book | 0.5 to 1 mg is often enough; high doses over 5 mg are not recommended |
| MedlinePlus | 3 to 5 mg during a flight that overlaps your destination bedtime, then several hours before bedtime for several days |
The two sources differ, so ask your clinician which fits you. The CDC also warns that melatonin is not regulated by the FDA, so the amount may differ from the label.
What About Sleeping Pills And Stimulants?
The CDC says hypnotics such as zolpidem and eszopiclone are options but their half-lives and side effects should be considered. The AASM parameters make short-term use of a hypnotic an option for jet lag insomnia and note adverse effects. The CDC says antihistamines and long-acting benzodiazepines should be avoided because they can worsen cognitive impairment and raise the risk of falls. Caffeine has a half-life of about 5 hours, so avoid it in the hours before bed. Check your own cutoff with the caffeine impact on sleep calculator.
What Is A Simple Jet Lag Plan?
- Days before: shift sleep 1 hour a day toward the destination for 2 to 3 days.
- On the flight: follow destination time for meals and sleep, drink water, and skip excess alcohol.
- On arrival: get natural light and stay awake until the local evening.
- If you nap: limit it to 20 to 30 minutes.
- Next days: keep a steady bedtime and wake time. See how social jet lag works if your schedule keeps shifting.
The CDC says that for short trips where adaptation would be limited, you can also keep your home sleep hours. That choice can make sense for a two-day meeting, where your body would barely start to adjust before you fly home.
When To See A Doctor
Talk to a clinician if you plan to use melatonin or a sleep medicine and take other medicines, if you travel often, or if sleep problems continue and seem out of proportion to your trip. The sources we used do not give a set number of days after which jet lag counts as a problem, so do not wait indefinitely if you feel unwell.
The CDC notes that frequent travelers face added effects from chronic insufficient sleep and circadian disruption. If low mood or anxiety accompanies poor sleep and you feel unsafe, call or text 988 in the US.
FAQs About Jet Lag
How Long Does Jet Lag Last?
It depends on direction and distance. The CDC gives average adaptation rates of 1.5 hours a day going west and 1 hour a day going east.
Is Jet Lag Worse Flying East Or West?
East, says the CDC, because it is harder to move the body clock earlier than later.
How Much Melatonin Should I Take For Jet Lag?
The CDC says 0.5 to 1 mg is often enough and advises against doses above 5 mg. MedlinePlus mentions 3 to 5 mg in one case. Ask your clinician.
Should I Avoid Alcohol On Flights?
The CDC advises avoiding excess alcohol, since it fragments sleep and adds to dehydration.
Can I Prevent Jet Lag?
You can reduce it. Shifting sleep for 2 to 3 days before the trip and using light at the right time may cut the adjustment time.
Your Next Step
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