Patients Are Asking: Does Flying Increase My Risk for Clot?

Key Takeaways

• The chance of getting a blood clot from traveling is small but some people have a higher risk, like those who are overweight, older, or pregnant.

• To lower the risk of getting a clot when traveling by plane, experts recommend moving around every 1-2 hours and drinking lots of water.

• People at higher risk may need to wear compression stockings or talk to their doctor about taking medicine to prevent blood clots.

Dr. Susan Kahn

Long-distance travel may raise your stress level, but can it also raise your risk of getting a blood clot?

To learn more, we spoke to Dr. Susan Kahn, a Professor of Medicine at McGill University and a Canada Research Chair in venous thromboembolism (VTE).

How does plane travel increase my risk of getting a blood clot?

Blood clots affect about 1-2 in 1,000 Americans per year, and the risk may double or triple after a flight that’s 4+ hours. Some studies estimate that 1 in 4,600 travelers will have a blood clot within 4 weeks of a long flight.

According to Dr. Kahn, “the risk of a travel-related blood clot is quite small, and the average traveler doesn’t need to worry about it. Billions of people travel by plane every year, and most of them don’t get a blood clot.”

However, those who already have risk factors for a clot may have a higher risk of developing travel-related VTE. These risk factors include:

• Obesity

• Age over 40

• Use of birth control pills or hormone therapy

• Recent injury or surgery (within last 3 months)

• Limited mobility

• Pregnancy and up to 3 months after birth

• A personal or family history of blood clots

• Active cancer or recent cancer treatment

It’s unclear if long-distance air travel is any riskier than car or train travel, but there are factors unique to airplanes that can affect risk:

• Air travelers sit in a tight space with the back of the knee pressed against the seat. The vein behind the knee is a common area for clots to form.

• Immobility can raise the risk of a clot. Your seat assignment, turbulence, and other factors can make it difficult to move around easily.

• Your body takes in less oxygen when the air pressure low. Some data suggest that lower oxygen levels can trigger the body’s clotting response.

• Dehydration can also increase the risk of a clot. Drinking coffee or alcohol on a flight can fast-track dehydration.

• Many people sleep on flights – and if you’re sleeping, you aren’t moving or hydrating. 

How can I reduce my risk of getting a blood clot?

The good news is that there are several commonsense methods recommended by clinical guidelines that can help lower your risk:

• Choose a bulkhead seat, try booking an aisle seat, or ask if your flight offers extra-legroom seating.

• Try to move around the plane every 1-2 hours.

• Avoid sleeping in awkward positions for long periods of time.

• Try not to cross your legs.

• Avoid wearing tight clothing.

• Drink lots of water and avoid alcohol, caffeine, and sedatives.

• Do some simple exercises in your seat to improve blood flow.

“For the average healthy person taking a long flight, we don’t recommend anything other than commonsense measures, like walking around the plane and staying hydrated,” explains Dr. Kahn.

Since there’s still a limited amount of data on travel-related VTE, the right course of action may be different for each person.

The Bottom Line

Travel-related blood clots are rare BUT moving around and staying hydrated are two ways to stay healthy – both in flight and on the ground. Talk to your doctor if you’re concerned about developing a blood clot while traveling.