Many Americans will travel afar to celebrate the holidays, potentially putting themselves at risk for deadly blood clots.

Sitting for long periods in a car or airplane can limit blood circulation and cause a condition called deep vein thrombosis (DVT). In DVT, blood clots form in the deep veins of the lower legs and thighs.

A clot can travel through the bloodstream and lodge in the brain, lungs, heart and other areas, causing severe organ damage and even death.

But deep vein thrombosis is easy to prevent.

If you plan to travel overseas or cross-country, make sure you get up and walk around at least every two hours, and try not to sleep more than four hours at a time. Drink plenty of water or juices, wear loose-fitting clothing, eat light meals and limit alcohol consumption.

If you’re a senior or have circulation problems, it’s also a good idea to wear compression stockings. They will help prevent clots from forming.

If it’s not possible to get up and move every couple of hours, he suggested this workout while sitting down: Extend both legs and move both feet back and forth in a circular motion. Move the knee up to the chest and hold the stretch for at least 15 seconds. Put both feet on the floor and point them upward, and then lift both heels as high as possible.

Deep vein thrombosis affects about 2 million Americans a year, and nearly 200,000 die, according to the heart center.

Symptoms include pain and tenderness, swelling, redness, and increased warmth in one leg. In some cases, a physician might suggest that a patient go on blood thinners or simply take an aspirin before and during a long trip to avoid DVT.

People who are pregnant, or who have a history of heart disease, cancer or blood clots should always consult with a doctor before a long trip.