You’ve probably heard there’s a link between blood clots and flying. But what does that mean for you and your future flight plans? Read on to learn everything you need to know about blood clots, your risk, and how to prevent them when flying.

When talking about the risk of blood clots while flying, it’sdeep vein thrombosis (DVT) that’s of particular concern. DVT is a potentially life-threatening condition in which a blood clot forms in one of your body’s deep veins, typically in one of your legs. These clots are extremely dangerous. They can break off and travel to your lungs, leading to a condition known as pulmonary embolism (PE).

In some cases, DVT may not present symptoms, while others may experience:

  • swelling in the foot, ankle, or leg, usually only on one side
  • cramping pain, which typically begins in the calf
  • severe, unexplained pain in the foot or ankle
  • a patch of skin that feels warmer to the touch than skin surrounding it
  • a patch of skin that turns pale, or turns a reddish or bluish color

Signs of a PE may include:

  • dizziness
  • sweating
  • chest pain that becomes worse after coughing or deep inhales
  • rapid breathing
  • coughing up blood
  • rapid heart rate

Symptoms of DVT and PE, collectively referred to as venous thromboembolism (VTE), may not occur for several weeks after a flight.

Sitting for extended periods of time in cramped airplane seats may slow blood circulation and increase your risk for DVT. Prolonged inactivity and dry cabin air seem to contribute to the risk.

While there’s some debate as to the connection, some studies have found evidence that the prevalence of DVT within 48 hours of flying on a plane is 2 to 10 percent. That’s the same rate that people in hospitals develop DVT. Staying in a hospital is another risk factor for DVT.

The risk, however, varies greatly among passengers. In general, the longer the flight, the higher the risk. Flights lasting more than eight hours are thought to pose the most risk.

You’re more likely to develop DVT while on a plane if you have any of the other risk factors for it. These include:

  • being over age 50
  • having veins that have been damaged in an injury in the lower extremities, such as from a fractured bone
  • being overweight
  • varicose veins in your legs
  • having a genetic clotting disorder
  • having a family history of DVT
  • having a catheter placed in a vein in the lower extremities
  • taking birth control pills
  • undergoing hormone therapy
  • being pregnant or having given birth in the past month
  • smoking

Flying after blood clots

If you’ve received a diagnosis of DVT in the past or have a family history of blood clots, you’re at an increased risk for developing them while flying. That doesn’t mean you’ll never be able to fly again. Some experts recommend waiting to fly on an airplane for at least four weeks after having DVT or PE, but talk to your doctor about this.

Also talk to your doctor to determine what precautions you should take before flying. In addition to general recommendations for preventing blood clots, they may suggest the following precautions:

  • sitting in an exit row or bulkhead seat to increase legroom
  • wearing compression stockings
  • taking prescription blood thinners or aspirin
  • using a foot or calf pneumatic compression device, which fills with air and squeezes your legs to increase blood flow through the veins
  • exercises for your feet and legs while flying

If you have any of the symptoms of DVT, or are at high risk of developing it, see your doctor for an evaluation. DVT and PE may not occur for several days and up to two weeks after travel.

In some cases, DVT will resolve on its own. In other cases, however, treatment will be necessary. Treatment may include:

  • medication, such as blood thinners and those that break up clots
  • compression stockings
  • the placement of a filter inside the body to stop clots from entering your lungs

You can reduce your risk for DVT by taking some precautions during a flight:

  • move around as often as possible by walking in the aisles when allowed
  • avoid crossing your legs
  • avoid wearing tight clothes that can restrict blood flow
  • stay hydrated, and avoid alcohol before and during travel
  • stretch legs and feet while sitting

There are also some exercises you can try while seated. These may help keep your blood flowing and reduce your risk for clots:

  • Extend your legs straight out in front and flex your ankles. Pull up and spread your toes, then push down and curl your toes. Repeat for 10 times. Remove your shoes if necessary.
  • If there isn’t room to extend your legs, start with your feet flat on the floor and push down and curl your toes while lifting your heels from the floor. Then, with your heels back on the floor, lift and spread your toes. Repeat 10 times.
  • Exercise your thigh muscles by sitting with your feet flat on the floor and sliding your feet forward a few inches, then sliding them back. Repeat 10 times.

DVT is a serious condition that can become life-threatening if not treated. Flying may increase your risk for developing DVT, but the risk is low for most people.

There are simple steps you can take to minimize your risk depending on your health history. Knowing the signs and symptoms of DVT and PE and taking steps to reduce your risk are the best ways to fly safely.