How to Deal With Jet Lag: Resetting Your Body Clock After Travel

What is actually happening in your body during jet lag?

Your circadian rhythm is a roughly 24-hour internal clock embedded in nearly every cell of your body, coordinated by a region of the brain called the suprachiasmatic nucleus. It regulates when you feel sleepy and alert, when your body temperature rises and falls, and when hormones like cortisol and melatonin are released.

The primary signal that synchronizes this clock to the local environment is light — particularly morning light. When you cross multiple time zones rapidly, the local light-dark cycle shifts, but your internal clock can only move gradually — roughly one to one-and-a-half hours per day. Eastward travel (requiring your clock to advance — sleeping and waking earlier) is typically harder than westward travel (requiring your clock to delay), because advancing against the clock's natural drift direction is physiologically more difficult.

How does light help reset the circadian clock after travel?

Bright light is the strongest known zeitgeber (time-giver) — the environmental signal that shifts the circadian clock most effectively 3Ref 3Ashton A, Foster RG, Jagannath A (2022).Photic Entrainment of the Circadian System.Light as the primary zeitgeber (time-giver) for circadian clock entrainment via the suprachiasmatic nucleus; explains why light timing at destination is the key lever for resetting after transmeridian travel.

After eastward travel (e.g., US to Europe): Your clock needs to advance — you need to feel sleepy and wake up earlier. Getting bright outdoor light in the morning at your destination helps. Avoid bright light in the evening for the first day or two.

After westward travel (e.g., Europe to US): Your clock needs to delay — you need to stay awake later. Bright light in the late afternoon and evening at your destination helps. Avoid strong morning light initially, which would push your clock in the wrong direction.

This logic can reverse for very large time zone differences (more than 8–9 zones), which is why apps designed for jet lag management that account for both direction and number of zones crossed can be useful.

Does melatonin help with jet lag — and how should it be used?

A Cochrane review found that melatonin is effective for preventing and reducing jet lag, particularly for eastward travel across five or more time zones 1Ref 1Herxheimer A, Petrie KJ (2002).Melatonin for the Prevention and Treatment of Jet Lag.Melatonin is effective for preventing and reducing jet lag, particularly for eastward travel across five or more time zones. It works by shifting the circadian clock when taken at the right time — not simply as a sedative.

For eastward travel: taking low-dose melatonin in the early evening at the destination (aligned with local, not home, time) can help advance the clock. For westward travel: melatonin timing is less straightforward and is sometimes unnecessary if you can naturally extend wakefulness.

The dose that shifts the clock is generally low — often lower than what most over-the-counter products contain. Higher doses primarily produce sedation rather than meaningful clock-shifting and may cause next-day grogginess. Discussing dose and timing with a clinician or pharmacist is worthwhile, particularly for frequent travelers. Melatonin should not be used during pregnancy without medical guidance.

What other strategies help reduce jet lag?

Adjust your schedule before departure. If traveling east, going to bed an hour earlier for a few days beforehand softens the adjustment. Westward travelers can do the reverse.

Stay hydrated and minimize alcohol on the flight. Both dehydration and alcohol fragment sleep and worsen recovery on arrival. Cabin air is dry; drink water throughout.

Sleep on the plane strategically. Try to sleep during what will be nighttime at your destination, using a sleep mask and earplugs to block the opposite-phase light and noise.

Anchor to local meal times. The digestive system has its own circadian rhythm. Eating at local times — even if hunger does not match — helps re-synchronize peripheral clocks alongside the central brain clock.

Get outside during the day. Natural light at your destination simultaneously shifts your clock and helps you stay awake through local daytime.

Avoid long naps at the wrong local time. If you need rest, keep naps under 30 minutes and avoid them in the late afternoon locally.

How long does jet lag typically last?

Without any active strategies, the clock adapts roughly one to one-and-a-half hours per day. A five-zone eastward trip can take four to five days to fully resolve; a ten-zone difference can take close to a week.

Adaptability decreases with age — older adults typically find jet lag more severe and slower to resolve than they did in earlier life, which is a real biological difference 2Ref 2National Institute on Aging (2023).Sleep and Older Adults.Circadian adaptability decreases with age; older adults find sleep disruption — including jet lag — more severe and slower to resolve. Eastward travel is consistently harder for most people. Frequent long-haul travelers who find that symptoms no longer fully resolve between trips should discuss this pattern with a clinician, as persistent circadian misalignment has its own health implications.