Jet lag is what happens when the sun tells your body one time and your watch tells it another. Cross enough time zones and your circadian clock — the internal system that governs sleep, hormone release, digestion, and cognition — falls out of sync with the local day. The result is fragmented sleep, daytime fog, GI upset, and a general sense of being slightly off for anywhere from a few days to more than a week.
Recovery is largely a matter of moving your clock in the right direction as quickly as possible. Most of the useful interventions are simple, cheap, and involve light, food, and timing rather than medication.
Direction matters more than distance
A useful rule of thumb: your body shifts about one time zone per day naturally, and eastward travel is harder than westward. Flying east requires you to fall asleep earlier than your body wants — a phase advance — which is biologically the tougher direction. Flying west asks you to stay up later — a phase delay — which most bodies tolerate more easily.
This matters because the interventions differ. For eastward travel, you want morning light at the destination and to avoid evening light. For westward travel, you want evening light and to avoid too-early-morning light.
Use light, then food, then melatonin
Light is the strongest signal to your circadian clock. Get outside at the destination during the local morning if you flew east, and during the local afternoon and early evening if you flew west. Even on an overcast day, outdoor light is orders of magnitude brighter than most indoor lighting, and the effect on the clock is proportionally larger.
- Eastward trips: seek morning sunlight, avoid bright light in the late evening for the first few days
- Westward trips: seek afternoon and evening sunlight, avoid intense light before dawn
- Meal timing: eat on the local schedule from arrival, even if you are not particularly hungry
Melatonin, taken in low doses (0.5 to 3 mg) in the hours before your target local bedtime, can help nudge the clock along. It is not a sleeping pill in the usual sense — its main value is as a circadian signal, not sedation. Taking it at the wrong time of day can actually push your clock the wrong way.
The interventions that work for jet lag are the ones that speak to your circadian system in its own language: light, dark, food, and, in small doses at the right time, melatonin.
The flight itself
Stay hydrated and move around when you can. Skip alcohol — it fragments sleep and worsens dehydration. Whether to sleep on the plane depends on whether it is nighttime at your destination during the flight; if so, sleep, and if not, try to stay awake. Set your watch to destination time when you board to start orienting mentally.
Short strategic naps at the destination are fine if you are dangerously sleepy, but keep them under about 30 minutes and avoid napping in the late afternoon, which will make the coming night worse.
When jet lag will not lift
For most travelers, jet lag resolves within a few days to a week. If your sleep remains fragmented or you are severely impaired past that window, consider:
- Circadian misalignment: you may be inadvertently exposing yourself to light or eating at times that hold the clock in place. Audit your day.
- Underlying insomnia: travel can unmask a sleep problem that was manageable at home
- Sleep apnea or another disorder: worth a workup if fatigue persists well beyond the trip
Caffeine can help you function during the adjustment window, but the same rules apply as at home: cut it off well before your target local bedtime, or you will delay adaptation.
The bottom line
Jet lag is a circadian problem, and it responds to circadian tools. Get outside at the right times of day for your travel direction, eat on the local schedule from arrival, and use low-dose melatonin at your target bedtime if you want a small extra nudge. Most people are functional within two to three days and largely recovered within a week.