There are a number of situations we, as travelers, consider when planning our vacations. We carry copies of our passports in case the originals get displaced or carry traveler’s checks that offer more security than cash. We call ahead to notify our credit card companies and banks that we’ll be out of the country so that they don’t alert us to fraud. But what about one very real risk that we rarely plan for is the risk of deep vein thrombosis, or DVT.

While travel isn't the only risk factor for DVT (and other risk factors, including pregnancy, smoking and age are significant), long trips by car or plane can put us at risk for developing this potentially life-threatening condition, despite an otherwise clean bill of health. For those of us with additional risk factors, long trips can increase our risk of developing DVT.

What Is DVT?

DVT is a blood clot that forms in a vein deep in the body, typically in the lower leg or thigh. In some cases, it causes the vein to swell, a condition called thrombophlebitis; in others, there are no symptoms. The real risk of developing DVT, however, isn’t just in the danger to the limb or vein affected -- it’s that the clot can break free and cause a life-threatening blockage in the lung, called a pulmonary embolism.

What Causes DVT?

While some causes of DVT are linked to genetics and medical conditions that affect the way your blood clots, sitting still for long periods of time -- whether because of a long trip, after a surgery, or because of limited mobility caused by other health conditions -- can greatly increase your risk of developing DVT. There are many factors that can increase your risk of developing DVT, and the more you have, the greater your risk. Among these:

Sitting for Long Periods of Time

When you’re sitting for long periods of time, your calf muscles don’t contract - which is something that helps with leg circulation. When this happens, you risk having blood clots form in your legs.