Jet Lag
Jet lag is a temporary sleep disorder caused by crossing multiple time zones faster than your body can adjust.
Jet lag is a temporary sleep disorder caused by crossing multiple time zones faster than your body can adjust.
Also known as
Circadian rhythm disruption, Time zone fatigue, Desynchronosis
Why travellers need to know
Jet lag affects decision-making, reaction times, and immune function. For travellers managing chronic conditions, it also disrupts medication schedules. Eastward travel is harder than westward because compressing your day is more difficult than extending it. A general rule: it takes roughly one day per time zone crossed to fully adjust. Melatonin, light exposure timing, and strategic caffeine use all help.
Real-world example
You fly from London to Tokyo (9 hours ahead). You arrive at 10am local time but your body thinks it's 1am. You're exhausted but force yourself to stay awake until 9pm. By day 3 you're mostly adjusted. Your colleague who napped until 4pm on arrival is still waking at 3am a week later.
Country-specific notes
🇯🇵 Japan
Melatonin is not sold over the counter
Japan treats melatonin as a medicine, not a supplement, and it is not sold over the counter. If you use it for jet lag, bring your own supply and check the Ministry of Health, Labour and Welfare's personal-import rules.
🇬🇧 United Kingdom
Melatonin is prescription-only
In the UK, melatonin requires a prescription (usually under the brand Circadin). If you rely on melatonin for jet lag, bring your own supply from a country where it is OTC and carry it with the packaging and your medication list.
🇦🇺 Australia
Australia's timezone distance from Europe and the Americas makes jet lag particularly severe — 8–10 hour time differences are common
Flying in from Europe means travelling east, which is usually harder to adjust to than flying west. Expect to need several days to adjust fully. Morning daylight is the strongest circadian reset signal available.
Expose yourself to outdoor morning light on the first 2–3 days in Australia — daylight at breakfast time is the most effective way to reset your body clock.
Frequently asked questions
Does jet lag affect medication timing?
Yes, particularly for time-sensitive medications like insulin, blood pressure medication, and oral contraceptives. Discuss a transition schedule with your doctor before travel. The general approach is to shift gradually toward destination time over 2-3 days.
Is melatonin effective for jet lag?
Evidence supports melatonin for reducing jet lag symptoms, particularly for eastward travel. Take 0.5-5mg at destination bedtime starting the day of arrival. It's sold over the counter in the US and Canada, needs a prescription in the UK and Australia (apart from pharmacist supply of one product to adults 55 and over in Australia), and rules vary across the EU.
Nomedic stores your medication schedule so you and your doctor can plan timing adjustments for long-haul travel.