Preventing DVT on Long Flights: Blood Clot Risks and Precautions

Deep vein thrombosis is a blood clot in a deep vein, usually in the leg. Sitting still for hours lets blood pool in the lower legs, which makes clots more likely. The danger is that part of a clot can break off and travel to the lungs, causing a pulmonary embolism.

The CDC notes that any trip longer than about four hours, by plane, car, bus or train, can raise the risk, though the absolute risk is small for most healthy travelers. The longer the journey, and the more risk factors you have, the more these precautions matter.

The CDC lists several factors that raise risk, and risk climbs when you have more than one.

Movement is the CDC’s core advice. Choose an aisle seat so you can get up easily, and walk around every couple of hours when the seat belt sign is off. While seated, raise and lower your heels and toes, and tighten and release your leg muscles.

Wear loose, comfortable clothing and stay hydrated. A lie-flat seat makes it easier to change position, but it doesn’t replace getting up; our guides to seat selection and long-haul flight tips cover comfort more broadly. If you take a sleep aid, ask your clinician first, since deep sleep in one position for many hours means less movement.

That’s a decision for you and a clinician, based on your risk factors. For travelers with added risk, a doctor may recommend properly fitted graduated compression stockings or, for higher-risk travelers, medication before departure.

Don’t self-prescribe. The CDC says taking aspirin to prevent blood clots when traveling isn’t recommended. If you’ve had a clot before or recently had surgery, discuss your travel plans well before you book.

Clots don’t always cause symptoms during the flight, so stay alert in the days after a long trip. Signs of DVT include swelling, pain or tenderness, warmth, and redness or discoloration, usually in one leg. About half of people with DVT have no symptoms at all.

Signs of a pulmonary embolism include difficulty breathing, a fast or irregular heartbeat, chest pain that worsens with a deep breath or cough, coughing up blood, and lightheadedness or fainting. Seek medical care immediately; abroad, our guide to emergencies abroad explains who to call.

Yes. On very long journeys, breaking the trip with a night in a hub city gives your body a real break and helps with jet lag too. Some airlines let you add a stop for no extra airfare; see stopover programs. Booking flights with reasonable connections, rather than back-to-back ultra-long sectors, is another easy win.