Thinking about getting away this summer? Then maybe you should consider how far you will need to travel to your destination. Researchers say for every two-hour increase in travel by car, bus, train or plane, the risk of developing a blood clot—also known as venous thromboembolism—increases nearly 18 percent.

In study results recently published in the Annals of Internal Medicine and reported on by Health News, researchers compared 14 previous studies that reviewed the rate of blood clots among travelers and nontravelers. Researchers found that there were twice as many blood clots among those who traveled.

Signs of a blood clot include, but aren’t limited to, reddened skin as well as pain, soreness and swelling in the legs and arms.

Can’t give up your wanderlust? Help prevent blood clots by drinking plenty of water and occasionally walking around while traveling.