Condition deep-dive · 5 min read

Jet Lag — supplement protocol for circadian re-entrainment

Updated 2026-05-19 · Reviewed by SupplementScore editors · No sponsorships

Jet lag — transient circadian misalignment after eastward or westward travel — has the cleanest supplement-evidence story of almost any condition. Low-dose melatonin (0.3–0.5 mg) taken at the right time of day relative to your destination is the most-evidenced supplement intervention in sleep medicine, supported by the AASM jet lag practice parameters. The biggest mistake travellers make is dosing 5–10 mg melatonin (sedates but doesn't phase-shift better) rather than low-dose timing-driven use, and ignoring light exposure (which dwarfs melatonin's effect size when used right).

The direction matters. Eastward travel (advancing clock — e.g. New York to London) is harder than westward travel (delaying clock — e.g. London to New York). Most people tolerate westward travel with light/caffeine adjustments alone. Eastward travel benefits more from formal pre-travel adjustment + melatonin timing. Trips of 1–2 time zones rarely warrant a full protocol.

The supplement stack — low-dose melatonin, timed correctly

Layer 1 · Primary intervention

Low-dose melatonin (0.3–0.5 mg) — destination bedtime timing

0.3–0.5 mg orally 30 minutes before destination bedtime; use for 3–5 nights post-arrival

The 2002 Cochrane review (Herxheimer & Petrie, 10 RCTs) found melatonin substantially reduces jet lag symptoms after eastward travel across 5+ time zones, with smaller effect for westward. Low-dose (0.3–0.5 mg) is the optimal trial range — higher doses do not work better and add next-day grogginess. Take 30 minutes before target destination bedtime each night for 3–5 nights. Start on the first night at destination.

Layer 1 · For eastward trips ≥6 time zones

Pre-travel phase advance (3 nights before)

0.5 mg melatonin 3–4 hours before usual bedtime, advancing 1 hour earlier each night × 3 nights pre-departure

For eastward travel of 6+ time zones (e.g. US East to East Asia, Europe to Southeast Asia), a 3-day pre-adjustment substantially shortens the post-arrival jet lag. Each night, take 0.5 mg melatonin 4–5 hours before your usual bedtime and try to sleep earlier; expose yourself to morning bright light. This shifts your internal clock partway before you fly.

Layer 2 · Strategic caffeine use

Caffeine — timed to destination morning

100–200 mg with destination breakfast/morning; avoid within 6+ hours of destination bedtime

Caffeine is an alertness aid for the first 4–5 hours of destination "day" — but caffeine has a 5–7 hour half-life and dramatically impairs sleep onset/quality if dosed late. Time it to destination morning, not your internal-clock morning. The 2018 AASM practice parameters specifically caution against late-day caffeine for jet lag.

Optional · For arrival-night sleep problems

L-Theanine + magnesium glycinate combination (arrival night)

200 mg L-theanine + 300 mg elemental magnesium glycinate, 30 min before arrival bedtime

If anxiety or restlessness disrupts arrival-night sleep onset (common with new-environment stress), L-theanine plus magnesium is a low-risk combination that supports calm without next-day grogginess. Use only the first 1–2 nights; don't extend into the re-entrainment window.

Optional · For long-haul flight (in-flight care)

Hydration + targeted in-flight strategy

~250 mL water/hour in flight; minimal alcohol; eat aligned with destination meals if possible

Not strictly a supplement, but the highest-leverage flight-side intervention. Cabin dryness, immobility, and alcohol exacerbate post-arrival fatigue. Adjust watch to destination time on boarding and follow meal/sleep cues accordingly.

The light-exposure layer (bigger than melatonin)

Strategic light exposure has a larger phase-shifting effect than melatonin and is the dominant zeitgeber. Get this right and the supplements become incremental.

Eastward travel: Seek bright morning light at destination (advances your clock). Avoid late-afternoon/evening bright light for the first 2–3 days, which would delay the clock and slow re-entrainment.
Westward travel: Seek late-afternoon/evening bright light at destination (delays your clock — the direction you want). Avoid early morning light for the first 2–3 days.
Brightness matters: Outdoor light (10,000+ lux) is dramatically more potent than indoor light (typically 100–500 lux). A 20–30 minute outdoor walk in the strategic-light window has more effect than any supplement.
For very long trips: Light-shifting glasses (timeshifter-style protocols) and light-blocking glasses (in the wrong-direction window) refine the protocol; not essential.

What to skip

High-dose melatonin (5–10 mg): Sedates but doesn't phase-shift better; adds next-day grogginess. The trial-evidenced dose is 0.3–0.5 mg.
Diphenhydramine ("PM" antihistamines) as sleep aid: Anticholinergic side effects, next-day cognitive impairment particularly in older adults. Not appropriate as a jet-lag tool.
Alcohol as a sleep aid: Worsens sleep architecture, dehydrates, and interacts badly with melatonin.
Z-drugs (zolpidem, eszopiclone) as routine: Have a role for some travellers in some situations (prescriber-directed), but routine use carries cognitive and dependence risks; melatonin + light is the first move.
"Anti-jet-lag" proprietary blends: Usually expensive overdosed melatonin with miscellaneous fillers; the trial-evidenced regimen is low-dose simple melatonin.
Adrenal-support / detox products: Not relevant to circadian biology.

Special populations

Children: Discuss pediatric melatonin use with a paediatrician; recent ER-visit-spike data argue for careful dosing and supervision.
Older adults: Lower-dose melatonin (0.3 mg) preferred. Adjust caffeine downward — slower metabolism means later half-life impact on sleep.
Pregnancy: Melatonin safety in pregnancy is poorly characterised; use only if symptoms substantially impair function, and discuss with obstetrics.
Bipolar or psychotic disorders: Discuss with prescriber; melatonin is generally safe but disrupted sleep is a destabiliser.
Active CV/CV-rhythm disease: Caffeine load adjusted; new arrhythmia evaluation if symptoms develop in flight.

Practical quick-start. Pre-flight: shift bedtime 1 hour toward destination for 2–3 nights if eastward 6+ zones. In flight: set watch to destination; hydrate; minimise alcohol; sleep aligned with destination night. On arrival: 0.5 mg melatonin 30 min before destination bedtime × 3–5 nights. Strategic light exposure — morning bright light eastward; late-afternoon/evening bright light westward. Caffeine 100–200 mg with destination morning, none within 6 hours of destination bedtime.

Educational reference, not medical advice. Discuss any supplement change with a qualified clinician before acting on this list. Frequent international travel with persistent sleep disruption warrants formal evaluation.