Long-Haul Flights: DVT Risk, Dehydration and Beating Jet Lag

According to the CDC, the risk applies to any journey over 4 hours — not only flights, but car, bus and train travel too. For most healthy travellers the absolute risk is low, but it rises the longer you stay immobile.

Who should take extra care

The CDC lists these risk factors. If one or more applies to you, speak to your doctor before the flight:

• A previous clot, or a clotting disorder in the family.
• Surgery or injury in the last three months, a leg in a cast, or limited mobility.
• Pregnancy and the first months after giving birth.
• Oestrogen-containing contraception or hormone therapy.
• Cancer or recent cancer treatment.
• Older age, obesity, varicose veins; heart or lung disease, or diabetes.

For people at risk, a doctor may suggest compression stockings or other measures. These are individual decisions — do not self-prescribe medication or choose stockings on your own.

Reducing clot risk in flight

• Move. The CDC recommends moving your legs frequently and walking the aisle at regular intervals. When the seatbelt sign is off and the crew allows it, get up.
• Exercise in your seat. Flex your ankles up and down, lift your toes, tense and release your calf muscles.
• Do not sit cross-legged for long stretches, and keep bags from pressing against your legs under the seat.
• Loose clothing — nothing tight at the waist or legs.
• Aisle seat makes getting up easier; pick it during online check-in.

Warning signs after a flight: swelling, pain, tenderness or warmth in one leg, or unexplained shortness of breath and chest pain. Seek medical help immediately if these appear — in Turkey the emergency number is 112.

Dry cabin air and dehydration

Cabin humidity is much lower than at ground level, which dries out skin, eyes and airways. Drink water regularly rather than in large amounts at once. Alcohol and a lot of coffee make dehydration worse and disturb sleep. If you wear contact lenses, consider glasses on a long flight, or carry drops. Lip balm and moisturiser are worth the cabin bag space.

Ears, sinuses and colds

Pressure changes during climb and descent can hurt if your sinuses are congested. Swallowing, yawning or chewing helps equalise; for babies, feeding during descent does the same. If you have a heavy cold or sinus infection, ask a pharmacist or doctor about a decongestant before flying — and reconsider flying with a severe ear infection.

Jet lag

Jet lag is the mismatch between your body clock and local time. It is generally worse flying east, when you must sleep earlier than your body wants, and milder flying west. It does not depend on distance but on the number of time zones crossed.

• Switch to destination time immediately — set your watch and phone when you board, and eat and sleep by the new clock.
• Use daylight. Morning light helps after eastward flights; afternoon and evening light helps after westward ones.
• Shift gradually before you go if the difference is large: move bedtime an hour earlier or later for a few days.
• Short naps only. A long afternoon sleep on arrival ruins the first night; 20–30 minutes is enough.
• Melatonin is used by some travellers; whether it suits you, in what dose and at what hour is a question for your doctor, not for the internet.

As a rough guide, the body adjusts about one time zone a day — so a six-hour difference takes several days to settle. If your trip is only two or three days, it can be easier to stay on home time as far as your schedule allows.

Medication, documents and special assistance

• Keep medicines in your cabin bag, in their original boxes, with the prescription or a doctor's note — checked bags get delayed.
• Liquid medicines over 100 ml are permitted with documentation, but declare them at security.
• Some countries restrict specific active ingredients; check the destination's rules for anything you carry.
• Pregnant travellers: airlines have their own limits by week of pregnancy and may ask for a medical certificate. Check before booking.
• If you need a wheelchair, oxygen, or help moving through the airport, request it from the airline at least 48 hours in advance.
• Travel insurance that covers medical treatment abroad is worth having on any long trip.

Before, during, after

• Before: sleep well the night before, start shifting your clock if the time difference is large, prepare medication and documents.
• During: water regularly, little alcohol, walk every couple of hours, ankle exercises in the seat, loose clothing.
• After: daylight and a normal meal schedule on the new clock; short naps only; watch for leg swelling or breathlessness in the following days.