Deep Vein Thrombosis (DVT)
DVT is a blood clot in a deep vein, usually in the leg, that can develop during long-haul flights or extended immobility.
DVT is a blood clot in a deep vein, usually in the leg, that can develop during long-haul flights or extended immobility.
Also known as
Economy class syndrome, Travel thrombosis, Blood clot, VTE (Venous thromboembolism)
Why travellers need to know
DVT risk increases on any journey over 4 hours where you're immobile: flights, buses, trains, or cars. Risk factors include previous DVT, recent surgery, pregnancy, oral contraceptives, obesity, and age over 40. Simple prevention measures (walking the aisle hourly, ankle exercises, hydration, compression socks) reduce risk significantly. Travellers on blood thinners or with clotting disorders should consult their doctor about flight-specific precautions.
Real-world example
After a 14-hour flight from London to Singapore, you notice your left calf is swollen, warm, and painful. At a clinic in Singapore, an ultrasound confirms a DVT. You're started on blood thinners immediately. If the clot had broken loose and reached your lungs (pulmonary embolism), it could have been fatal.
Country-specific notes
🇦🇺 Australia
Longest common flight routes increase DVT risk
Flights to Australia from Europe (22-24 hours) and the US East Coast (20+ hours) are among the longest in commercial aviation. Australian health authorities actively promote DVT awareness for inbound long-haul passengers.
Request an aisle seat for flights over 8 hours so you can walk the cabin hourly without disturbing others.
🇸🇬 Singapore
Changi Airport has DVT awareness signage and exercise areas
Singapore Changi Airport is a major long-haul transit hub with dedicated passenger exercise areas and DVT awareness campaigns. If transiting through Changi on a multi-leg long-haul journey, use the layover to walk and stretch.
🇬🇧 United Kingdom
UK NHS recommends compression stockings (15–30 mmHg) for flights over 4 hours for at-risk passengers
The NHS advises against aspirin for DVT prevention on flights — it is less effective than compression and carries side effects. Passengers with prior DVT, obesity, pregnancy, or recent surgery are most at risk.
Compression socks worn during a long-haul flight can be removed on arrival — the main DVT risk window is the flight itself, not the days after.
Frequently asked questions
Do compression socks actually prevent DVT?
Graduated compression stockings (15-30 mmHg) reduce DVT risk on long flights. They work by promoting blood flow in the legs. They're most beneficial for medium and high-risk travellers (previous DVT, recent surgery, pregnancy) but offer some protection for everyone on flights over 4 hours.
What are the warning signs of DVT after a flight?
Swelling in one leg (not both), pain or tenderness in the calf, warmth and redness in the affected area. Symptoms can appear up to 2 weeks after travel. If you develop sudden chest pain, breathlessness, or cough after a long flight, seek emergency care immediately as this may indicate a pulmonary embolism.
Your Nomedic record includes clotting risk factors, current medications, and contraceptive use, so any doctor can assess your DVT risk accurately.