Shift Work and Sleep: Coping With Night Shifts
Night and rotating shifts fight your body clock. A practical guide: anchor sleep, light, caffeine timing, naps, the drive home, and when to see a doctor.
Jet lag explained: why it happens and how to recover faster
You land at 8 am, and your body is convinced it is 2 am. That argument between the clock on the wall and the clock in your brain is jet lag — and it has rules you can use.
Published Updated 5 min read
What changed September 2026: added a light-timing table by direction and distance, melatonin dosing detail and in-flight advice.
On this page
Pending medical review
In short
Jet lag is a mismatch between your internal body clock and the local time after crossing time zones. Eastward travel is harder because it asks the clock to run earlier, which it resists; the clock shifts roughly an hour a day on its own. The fastest recovery comes from timing light exposure to the direction of travel, adopting local meal and sleep times immediately, keeping naps short, and, where appropriate, low-dose melatonin taken at local bedtime.
Key takeaways
- Rule of thumb: about one day of recovery per time zone crossed, less with good light timing.
- East is harder than west. Seek morning light after eastward flights; evening light after westward ones.
- Switch to local meal and sleep times from the first day; keep naps under 30 minutes.
- Melatonin has reasonable evidence for jet lag; timing (local bedtime) matters more than dose.
What jet lag is
Your body clock — the suprachiasmatic nucleus in the brain — runs a cycle of just over 24 hours and is reset each day mainly by light. When you cross time zones faster than the clock can adjust, everything it controls (alertness, body temperature, hunger, hormone timing) is out of step with local time. The result is the familiar mix of sleepiness at the wrong hours, wakefulness at 3 am, poor concentration and an unsettled stomach.
Left alone, the clock drifts toward local time by roughly an hour a day. With deliberate light timing you can shorten that considerably.
Why flying east is harder
Because the body clock naturally runs slightly longer than 24 hours, it finds it easier to delay (stay up later — what westward travel asks) than to advance (fall asleep earlier — what eastward travel asks). Toronto to London, Sydney to Los Angeles, and Vancouver to Frankfurt are all “hard direction” trips.
A practical plan
Before you fly
- For trips of three or more time zones, shift your bedtime and wake time 30–60 minutes a day toward the destination for two or three days beforehand — earlier for eastward, later for westward.
- Arrive rested. Starting with a sleep debt makes everything worse.
Light is the lever
Light in the morning (by your body’s clock) advances it; light in the evening delays it. So:
- After flying east: get bright light in the local morning and avoid bright light in the late evening. If the time difference is very large (8+ hours), avoid light in the first hours after local dawn on day one and seek it later in the morning, because your clock may still read “late night” at local sunrise.
- After flying west: seek light in the local afternoon and evening, and avoid bright light early in the morning.
Sleep, naps and meals
- Adopt local meal and bedtime from the day you arrive, even if you are not hungry or sleepy.
- If you must nap, keep it under 30 minutes and before mid-afternoon local time.
- Use caffeine in the local morning only; avoid alcohol on the flight — it fragments sleep and dehydrates.
Melatonin
Melatonin is one of the few supplements with reasonable evidence for jet lag, especially after eastward travel across five or more time zones. It works as a timing signal: a low dose (0.5–3 mg) at local bedtime for the first few nights. It is not a sedative, and people with certain conditions or on certain medications should check with a doctor or pharmacist first.
When it is more than jet lag
Jet lag resolves within days. Sleep that stays broken for weeks after travel, or was broken before it, is something else — see the insomnia guide. Frequent long-haul travellers with persistent sleepiness or snoring should also consider sleep apnea.
Light timing by direction and distance
The table below is a simplified version of the light-timing rules chronobiologists use. “Body-clock time” means the time your body still thinks it is on day one; it drifts toward local time over the following days, so shift the windows later (after eastward travel) or earlier (after westward travel) by about an hour a day.
| Trip | Seek bright light (local time) | Avoid bright light (local time) |
|---|---|---|
| Eastward, 3–6 zones (e.g. Toronto → London) | Morning, from shortly after local sunrise | Late evening |
| Eastward, 7–10 zones (e.g. Los Angeles → Paris) | Late morning and midday; sunglasses for the first 2–3 hours after local sunrise on day one, then move the window earlier each day | Early morning on day one; late evening |
| Westward, 3–8 zones (e.g. London → Vancouver) | Late afternoon and early evening | Early morning; stay up until a reasonable local bedtime |
| 11–12 zones either way (e.g. Sydney → Los Angeles) | Either direction works; most people adjust as if westward — seek afternoon and evening light and avoid early-morning light | Early morning |
| Short trips (1–2 zones, or 2 days or less) | Do not try to adjust: keep home-time meals and bedtime as far as the schedule allows, and use light and caffeine only to get through the day | |
Melatonin in more detail
The Cochrane review of melatonin for jet lag concluded that it is effective in reducing jet lag in adults crossing five or more time zones, especially eastward, when taken close to the target bedtime at the destination. Doses between 0.5 mg and 5 mg were similarly effective for the timing benefit; the higher doses helped people fall asleep faster but did not shift the clock more, and the review advised caution for people with epilepsy, on warfarin, or who are pregnant. Timing is the whole point — melatonin taken at the wrong time can push the clock the wrong way — so take it at local bedtime for the first few nights, not on the plane. Product quality varies widely between over-the-counter brands; the melatonin guide covers what to look for.
On the plane
- Set your watch to destination time as you board and start living on it: eat when the destination eats, sleep when it sleeps, if the flight allows.
- Skip alcohol; it fragments whatever sleep you get and dehydrates you. Water, and a light meal.
- An eye mask and earplugs for the destination night; move about and keep the shade up during the destination day.
- A short nap is fine on a westward flight; on an eastward overnight flight, try to sleep as much as you can — it is the destination night.
In summary
Jet lag is a timing problem and light is the timer. Pre-shift when you can, seek light at the right time of day for your direction, live on local time from day one, keep naps short, and consider low-dose melatonin at local bedtime for eastward trips.
Questions people ask
How long does jet lag last?
Roughly a day per time zone crossed if you do nothing; faster with deliberate light timing. Eastward trips take longer than westward.
Does melatonin help jet lag?
Reasonable evidence supports low-dose melatonin (0.5–3 mg) at local bedtime for a few nights, particularly after eastward travel across five or more time zones. Check with a doctor or pharmacist if you take other medication.
Should I stay awake on arrival?
Aim to follow local time. If you arrive in the morning, stay up with the help of daylight and a short nap at most; if you arrive in the evening, go to bed at a normal local hour.
Sources
- CDC Yellow Book — Jet lag
- American Academy of Sleep Medicine — Jet lag (patient information)
- Herxheimer A, Petrie KJ. Melatonin for the prevention and treatment of jet lag. Cochrane Database Syst Rev. 2002;(2):CD001520
- Sack RL et al. Circadian rhythm sleep disorders: part I, basic principles, shift work and jet lag disorders. An AASM review. Sleep. 2007;30(11):1460–1483
- Eastman CI, Burgess HJ. How to travel the world without jet lag. Sleep Med Clin. 2009;4(2):241–255
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