Jet lag

Jet lag is your body clock running on home time after you fly. Timed light, a shifted sleep schedule and, where allowed, melatonin can cut it short.

• Evidence: Some
• Medium effort
• Low cost
• Works: 2–7 days

Why it matters

Jet lag happens because your internal clock is still set to where you came from. Depending on how many time zones you cross and in which direction, it can take days to line up again [2].

How fast does it adjust? A review by two circadian researchers gives average rates of about 57 minutes per day after flying east and about 92 minutes per day after flying west [4]. Flying east is usually harder because your clock has to move earlier, and most people’s clocks shift later more easily than earlier [5].

Light is the main tool. Bright light in your body’s late evening and night moves your clock later. Bright light in your body’s early morning moves it earlier [6]. Those times are on your body’s clock, which is still on home time when you land.

How to do it

Before you go

1. Flying east: start shifting earlier. In a study of 28 young adults, moving sleep 1 hour earlier each day for 3 days, plus bright light for the first part of the morning, shifted their clocks about 2 hours earlier. Without the bright light the shift was only about half an hour [5]. Going outside in the morning is a free source of bright light [4].
2. Flying west: start shifting later. Go to bed and get up later for a few days, and get bright light in the evening before bed [4].

When you land

1. Sleep on local time. A planned sleep schedule is one of the AASM’s recommended options for jet lag [1].
2. Flying east: get morning daylight at your destination and keep evenings dim [4]. But after a very long eastward flight (more than 8 time zones), early morning light can hit the wrong part of your clock and slow adjustment [2]. On those trips, avoid bright light in the early morning for the first day or two.
3. Flying west: get light in the evening, and avoid bright light soon after waking for the first few days [4]. After a very long westward flight, though, late evening light can also slow adjustment [2].

Melatonin

A Cochrane review of 10 trials found that melatonin taken close to the target bedtime at your destination (10 p.m. to midnight) reduced jet lag after flights across 5 or more time zones in 9 of them. Doses of 0.5 to 5 mg worked about as well as each other, though people fell asleep faster on 5 mg. Doses above 5 mg didn’t help more. Benefit was larger the more zones crossed, and smaller flying west. For every 2 people who took it, about 1 benefited [3]. The AASM rates timed melatonin as a standard treatment for jet lag disorder [1].

Safety:

• Timing matters. Taken early in the day, it can make you sleepy and slow your adjustment [3].
• Legal status varies. In the UK it’s prescription-only [7]. In the US it’s sold as a dietary supplement and isn’t FDA-approved for jet lag [4]. Rules differ elsewhere, so check before you travel.
• Check with a doctor or pharmacist first if you have epilepsy or take warfarin: case reports suggest harm in these groups [3]. The same applies if you’re pregnant or breastfeeding, or take any regular medication.

More on doses, side effects and interactions: melatonin.

Common mistakes

• Getting light at the wrong time. It pushes your clock the wrong way [6][2].
• Taking melatonin in the afternoon to “get ahead”. It makes you sleepy and can delay adjustment [3].
• Alcohol on the flight to help you sleep. It won’t help your clock adjust; see alcohol for what it does to sleep.

Effect on your sleep score

• Timing and regularity: expect these to look worse for several days while your sleep moves to local time.
• Time to fall asleep, wake-ups and total sleep: usually worse for the first nights. In the Cochrane review, people fell asleep faster and slept better on 5 mg melatonin than on 0.5 mg [3]. We found no study measuring jet lag with consumer wearables.
• HRV and resting heart rate: no study we found measured this.

How confident: high that timing scores drop and recover; low for the size of other changes.

Evidence

Rated Some. The AASM guidance supports planned sleep schedules and timed light for jet lag (as options) and timed melatonin (as a standard) [1]. The Cochrane melatonin review pooled 10 trials, but it dates from 2002 [3]. The light advice is based on well-understood lab science [6] and small studies of simulated travel, like the 28-person pre-flight study [5], rather than large trials in real travellers. The adjustment rates are averages; yours may differ [4].

General information for healthy adults, not medical advice. If you have a sleep problem that lasts, read when to see a doctor. Sources checked 4 October 2026. Spot a mistake? Tell us.