Jet lag
Jet lag is the mismatch between your body clock and local time after a fast flight across several time zones.
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Medicines commonly prescribed for Jet lag
For informational purposes only. Always consult a doctor before using any medicine.
Dosage form: TABLET, 10 mgActive substance: zolpidemManufacturer: Sanofi Aventis S.A.Prescription requiredDosage form: TABLET, 10 mg zolpidem tartrateActive substance: zolpidemManufacturer: Laboratorios Cinfa S.A.Prescription requiredDosage form: TABLET, Zolpidem Tartrate 10 mgActive substance: zolpidemManufacturer: Viatris Pharmaceuticals S.L.U.Prescription required
Jet lag is the mismatch between your body clock and local time after a fast flight across several time zones. The body carries on living by the hour it left: it asks for sleep in the middle of the afternoon and refuses to let go in the evening, when the new place has long since gone to bed. What sets it apart from ordinary travel tiredness is how long it lasts. Tiredness clears after one decent night, whereas the body clock shifts no faster than about an hour a day, and for all that time you are living out of step with everyone around you.
Why flying east is harder than flying west
The daily rhythm is run by a small area of the brain that sets its time mainly by light: bright morning light moves the clock forward, evening light moves it back. In most people this internal clock runs on a cycle slightly longer than a day, so stretching the day out is easier for the body than cutting it short. Hence the one rule worth remembering: after flying west you catch up with local time at roughly a day per zone crossed, while after flying east it takes noticeably longer.
Jet lag starts once two or three zones have been crossed and gets worse with the number. A north-to-south flight leaves the body clock alone even if it takes twelve hours: what changes there is the climate and the height of the sun, not the time of day. Adjusting tends to get harder with age, and late risers usually cope better with westward trips while early risers settle faster after flying east.
What it feels like
The picture is fairly recognisable:
- you cannot drop off in the evening, and sleep breaks up in the small hours;
- daytime sleepiness comes over you, sometimes in the middle of a conversation or a meal;
- your head works less well than usual: absent-mindedness, silly mistakes, slowed reactions, which shows on the first day behind the wheel;
- irritability, flat mood, a heavy, cotton-wool feeling in the body;
- the stomach and bowel are off schedule too: appetite turns up at odd hours, and there may be nausea, heaviness, constipation or, conversely, loose stools;
- in small children the same thing looks like tantrums, night waking and refusing food.
The first two or three days are the worst, after which the symptoms fade on their own. If disturbed sleep drags on for weeks once you are back in your usual routine, the flight is no longer the reason.
What to do before you fly and on the way
Jet lag cannot be avoided altogether, but it can be softened considerably, and the work starts at home.
- Do not set off already short of sleep. Sleep loss on its own produces half of these symptoms, and afterwards there is no telling the two apart.
- Two or three days before the flight, move bedtime and getting-up time by about an hour a day towards the new zone: earlier if you are flying east, later if you are flying west. Shift breakfast and dinner along with them, because meals are a signal to the body clock as well.
- If the trip is short, two or three days, the sensible thing is not to adjust at all: stay on home time and put anything important into the hours that are daytime back home. Otherwise you will finish adapting just as you fly back and pay for jet lag twice.
- On the plane, set your watch to the destination as soon as you take off and think about food and sleep in that time from then on.
- Drink water, get up and walk the aisle, flex your ankles in your seat. Go easy on coffee and alcohol: alcohol speeds up dropping off but wrecks the second half of the night and adds to dehydration.
- Sleeping in flight is worth it if it is night at your destination. If it is daytime there, better to sit it out with light, water and walking. An eye mask and earplugs help either way.
The first few days after you land
Light is the main lever; everything else works more weakly. If you have flown west, seek bright light in the evening and keep it dim in the morning, so the clock falls back faster. If you have flown east, stay out of strong sunlight in the early morning for the first few days: at that hour it can push the clock the wrong way. Get your light closer to the middle of the day instead, then lower the lighting and put the screens away in the evening. Once the clock has caught up after a few days, ordinary morning sun becomes an ally again.
The rest is simple things that add up. Eat by local time even without an appetite: breakfast when it is morning there helps as much as a walk. Be active during the day rather than late in the evening. A nap is allowed, but a short one and no later than the middle of the day, or you will be awake again at night. Always set an alarm: sleeping in until lunchtime is the surest way to stretch jet lag out over a week. Keep the bedroom cool and dark, and leave coffee to the first half of the day.
Melatonin and sleeping tablets
Melatonin is the hormone the body releases in the evening to tell the brain that it is time to sleep. As a medicine it works less as a sedative than as a time marker: the hour you take it matters more than the amount, and that hour is the evening by destination time. It helps most on eastward journeys. How it is sold varies from country to country: in some it is an over-the-counter supplement, in others prescription only, and the amount of active ingredient in supplements is not always consistent. Children are given it only when a doctor has prescribed it, and it is not something to start on your own in pregnancy or while breastfeeding. Anyone on anticoagulants or anti-epileptic medicines should ask about it separately.
Sleeping tablets are rarely needed for jet lag. They are worth discussing if sleep fails to settle over several nights and that is wrecking the trip, and then only as a short course: they are habit-forming and leave you dull and slow the next morning. They are not combined with alcohol. Taking one on the plane is a poor idea, since deep sleep in a seat means several hours of complete stillness.
If you take medicines at fixed times
The day you fly turns out shorter or longer than a normal day, so the timing of doses has to be worked out again. Sort this out before you leave rather than at the airport.
- Insulin and diabetes tablets: work out the plan for the travel day and the days after it with your doctor, and check your glucose more often than usual while travelling.
- Contraceptive pills: the interval runs from the previous tablet rather than from the local clock, and a sizeable shift in timing can weaken the protection. Check before the trip how to handle your particular regimen.
- Anti-epileptic medicines are not to be missed, all the more so because the sleep loss of a flight already raises the risk of a seizure.
- Anticoagulants, thyroid hormone and heart medicines are easiest kept on home time for the first days and then moved across gradually.
When the flight is not the reason
Jet lag itself is harmless, and the one real danger is putting down to it something that belongs elsewhere.
- Pain, swelling, tightness and warmth in one calf or thigh after hours of sitting on a plane is how a deep vein thrombosis shows itself. If breathlessness, chest pain on breathing in, coughing up blood or a faint are added to that, it is a clot on the lung and you call an ambulance; across Europe the single number is 112. The risk is higher after recent surgery, in pregnancy and after birth, on hormonal contraception, with cancer and in anyone who has had a clot before.
- Fever, diarrhoea, a rash or yellowing of the skin after you get back is not the aftermath of crossing zones but an infection, all the more so after the tropics. See a doctor the same day and say where you have been.
- If sleep has not settled two weeks into ordinary life at home, insomnia is worth addressing on its own terms rather than as a leftover of the trip.
- Loud snoring with pauses in breathing and stubborn daytime sleepiness call for a look at your breathing during sleep; the flight has nothing to do with it.
One more thing: for the first day after a long flight it is better not to drive and not to schedule anything where a mistake would be costly.
Online consultation
An online appointment is most useful before the trip, particularly a long one taken while you are on medicines with fixed timings. The doctor will help you recalculate insulin or other doses for the travel day, say whether melatonin is worth taking and at what hour, and judge whether adjusting at all makes sense in your case or whether staying on home time is wiser. They will also look at your risk of a clot on a long flight and what to do about it. After you return, an online consultation helps when it is unclear what is going on: the doctor will go over the dates, tell drawn-out jet lag apart from insomnia or an infection brought back with you, and say which tests are needed. But with swelling in one leg, breathlessness or chest pain nobody waits for an online consultation — you call an ambulance.
This material is for information only and does not replace medical advice.
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