Jet lag: what to do, when to see a doctor

Key takeaways

According to NHS, jet lag usually eases over a few days and cannot be prevented outright, only reduced. It is not something that needs treating.
The most useful thing after landing: eat, sleep and wake on local time from the first day, and get outdoors in daylight.
The easiest mistake for anyone on daily medication: according to CDC, doses go by the time elapsed since the previous one, NOT by the clock where you have landed. Ask your doctor BEFORE the flight.
Two national health agencies do not say the same thing about melatonin for jet lag — how much and when is a decision for a doctor or pharmacist.
Swelling or pain in ONE leg, breathlessness, chest pain, coughing up blood, or a fever after returning from abroad: that is not jet lag, and it is not something to sleep on and see.

Fly across several time zones and you will be tired, sleep badly and think slowly for a few days — most of that really is jet lag, and it passes on its own. The thing to watch runs the other way: a few conditions that follow a long flight look exactly like jet lag and are not.

Recognising jet lag

According to CDC, jet lag is a TEMPORARY sleep problem caused by the mismatch between your body clock and the time where you have arrived; it usually appears after crossing more than three time zones, and it affects mood, concentration and physical performance.

Difficulty falling asleep at bedtime, difficulty getting up in the morning.
Overwhelming tiredness; hard to stay awake during the day.
Shallow sleep — you sleep and still do not feel rested.
Trouble concentrating, forgetfulness.
According to NHS, it may come with indigestion, nausea, constipation and erratic appetite.

The direction of travel decides how it feels. According to CDC, flying EAST puts the clock ahead of you, so the body has to shift its rhythm earlier — that direction is harder; flying WEST means stretching it later. According to CDC, how badly it hits also depends on how many time zones you crossed, the light where you have arrived, and ANY MEDICATION YOU ARE TAKING.

What it gets confused with

Tiredness after a flight does not make ONE leg swell. According to CDC, sitting still for long periods lets blood pool in the leg veins — the signs of a clot are in the box below.
A FEVER after returning from abroad is not jet lag. Get seen and say exactly which country you have come from — this site has a separate article on malaria.

What to do right away

BEFORE you fly, nudge your bedtime in the direction you are travelling: according to CDC, go to bed an hour or two later for a westward trip, earlier for an eastward one.
After landing: eat, sleep and wake on local time from the first day — according to CDC, once the shift is more than three hours, follow the sleep-wake pattern of the place you have arrived in.
Get outdoors in daylight: according to NHS, natural light helps the body clock reset. Set an alarm so you do not oversleep.
If you are sleepy during the day, keep any nap genuinely short: according to CDC, no more than 15 to 20 minutes. Anything longer is taken out of the night.
Drink enough, eat smaller meals; on the aircraft, NHS advises stretching and walking about the cabin.
If something important is waiting, CDC suggests arriving at least two days ahead; for a trip of only a few days, NHS says staying on your home schedule is also reasonable.

Things NOT to do

Do NOT move your medication times onto local time by yourself. According to CDC, doses go by the time elapsed since the previous one, NOT by the clock where you have arrived; if the time zone changes, ask your doctor BEFORE the flight.
Do NOT drink alcohol to get to sleep, and no coffee or hard exercise in the evening. According to CDC, alcohol disrupts sleep; caffeine and exercise can be used but the timing matters. Both are also dehydrating, and dehydration makes jet lag worse.
Do NOT sleep off the whole afternoon. According to NHS, avoid sleeping during the day and sleep only at night.
Do NOT buy sleeping pills yourself to get through the first night, and do not take sleeping pills someone else hands you.
Do NOT put everything down to jet lag: tiredness and poor sleep fit; swelling in one leg, breathlessness, chest pain or fever do not.

Melatonin and sleeping pills

NHS explains that melatonin is a hormone the body releases in the evening to tell the brain it is time to sleep. On whether to take it as a tablet for jet lag, two national health agencies do NOT agree: NHS states plainly that it does not recommend it, because there is not enough evidence that it works.

CDC material written for clinicians, by contrast, lists correctly timed melatonin among the approaches for frequent flyers. Two sources disagreeing means this is exactly the kind of decision that belongs with someone qualified — how much and when is for a doctor or pharmacist. According to NHS, jet lag usually needs no medication at all; sleeping pills may help in severe insomnia but can lead to dependence, so they are used only for a short period.

When hospital care is needed

GO TO EMERGENCY CARE or call 115 (the emergency number in Vietnam) NOW if, after a long flight, there is: breathlessness · chest pain that gets worse on coughing or on a deep breath · coughing up blood · a pounding heartbeat, clearly faster than usual · severe light-headedness or fainting · confusion, rambling speech, difficulty rousing · a seizure. According to CDC, those are the signs of a clot that has travelled to the lungs — this is not something to sleep on and see. — SEE A DOCTOR WITHIN 24–72 HOURS if: swelling, pain or tightness in ONE leg with the skin there red and warm to the touch · sleep still broken after several weeks, or low mood that persists alongside it · you take medication daily and something has felt different since the flight. A FEVER after returning from abroad is separate: be seen the same day, and say exactly which country you have come from.

What can be done at home, and when to go in

Plainly: jet lag needs no treatment, it passes by itself. What needs someone qualified is a different question — whether this really is jet lag, and whether the medication you are on needs its timing adjusted.

If you are unsure whether to be seen, start with a remote consultation (a video call): describe the symptoms, show the doctor your leg if it is swollen, and get a view on what to do next. If an in-person examination is needed, a doctor comes to where you are staying, takes a history, examines you, and then says clearly whether to keep watching or to go in.

If you have brought medicines back from abroad or are about to travel, send photographs of the prescription and the boxes so we can check for duplicated active ingredients, interactions, and which products carry the same active ingredient in Vietnam — we advise, we do not sell medicines. A remote consultation is not for someone who is drowsy or has had a seizure: if any sign in the box above is present, go in first and call afterwards.

Sources: the US CDC (Travelers' Health: Jet Lag, Blood Clots During Travel, Traveling Abroad with Medicine; Yellow Book: Jet Lag Disorder) and the UK NHS (Jet lag). This article passes that guidance on and does not replace being examined; citing CDC and NHS here does not imply that CDC or NHS endorses Y Te Xanh or our services.

Need personalised advice for your loved one? Call our hotline 094 368 81 15 (24/7) — calling to ask a question or to book costs nothing. GreenCare has doctors who come to examine, nurses who carry out doctor's orders (injections, infusions, dressing changes), remote consultation by video call, and a review of the medicines you are taking; an in-depth remote consultation, or any one after the first, is a paid service. For children we take examination and acute care only — not long-term care at home, and not newborns or expectant mothers. We confirm we have staff in your area and provide transparent pricing before we begin.

Sources

CDC — Jet Lag
NHS — Jet lag

Frequently asked questions

How long is it normal for jet lag to last?

According to NHS, jet lag usually eases over a few days as the body adjusts to the new time. CDC material written for clinicians estimates that the body shifts by about an hour and a half a day flying west and about an hour a day flying east — so the more time zones you cross the more days it takes, and eastward is generally harder than westward. What matters is the trend: a little better each day is normal, getting steadily worse is not. Sleep still broken after several weeks, or low mood that persists alongside it, is a different matter and worth being seen for.

I take medication every day — which clock do I follow in another time zone?

Do not decide this yourself; it is the most important point in this article. According to CDC, medication should be timed by the interval since the previous dose, NOT by the clock where you have just arrived; and if you are travelling to a different time zone, ask your own doctor beforehand whether anything needs to change. Ask BEFORE the flight, because once you are at the airport there is no one left to ask. CDC also advises keeping medicines in their original labelled containers and carrying them in your hand luggage rather than checked baggage.

Can I take melatonin to help me sleep?

This article prints no dose, and the reason is specific: two national health agencies do not agree. NHS states that it does not recommend melatonin tablets for jet lag, because there is not enough evidence that they work; CDC material written for clinicians lists correctly timed melatonin among the approaches for frequent flyers. While the sources still differ, the person who decides has to be a doctor or pharmacist who knows what else you are taking — both the amount and the timing sit with them. If you have already brought a box back from abroad, the safe route is to have someone qualified look at the active ingredient before you take it.

One leg is painful and swollen after a long flight — is that just stiffness from sitting?

It must not be assumed to be. According to CDC, sitting for long periods without getting up lets blood pool in the leg veins, and the signs of a clot include swelling, pain or tightness in the affected area — usually a leg — along with skin that is red and warm to the touch. CDC says that if those signs are present you should be seen promptly, because finding and treating it early prevents death and complications. If it comes with breathlessness, chest pain that worsens on a deep breath, coughing up blood, a pounding heartbeat or fainting, call emergency services. To reduce the risk, CDC advises getting up and walking about periodically, and exercising the calf muscles and stretching the legs while still seated.

What do we do about the children travelling with us, who also have jet lag?

The principle is the same as for adults: move eating, sleeping and waking onto local time from the first day, get them outdoors in daylight, and do not let them sleep off the whole afternoon. What differs is this: do not give a child anything to help them sleep on your own initiative, including something an adult in the family uses — ask a doctor or pharmacist. To be clear about our scope: the service packages we currently offer are aimed at adults, and we do not provide paediatric or neonatal care, so for young children please see a paediatrician. A child with a fever, refusing food and drink, lethargic or difficult to rouse should be seen straight away, not filed under jet lag.