Frequent road trips home during college were a part of life for Mallory Click.
"I was trying just to drive straight through and get there...just so I wouldn't be wasting time driving," said Click.
But the five-and-a-half-hour trips nearly took her life at age 21.
"My leg was just throbbing, and I had a hard time sleeping that night. I was just kind of tossing and turning all night," said Click.
The pain and swelling were caused by deep vein thrombosis, a blood clot in her leg that nearly doubled its size and sent her to the emergency room.
"I would have never thought at such a young age I could get blood clots," she said.
DVT impacts two million people a year in the United States. Dr. Heather Hall, a vascular surgeon at Weiss Memorial Hospital, says most people know nothing about it or its risks.
"It's when that clot breaks off and travels to the lung and becomes a pulmonary embolism that it can be fatal," said Hall.
Every year, DVT kills more than 100,000 Americans, more than breast cancer and AIDS combined.
"Anything that makes a person less active or less mobile is going to put them at risk for developing a DVT," said Hall.
Her best advice when traveling or driving long distances is to stop every four hours to stretch your legs and get your blood flowing.
"If you're stuck on a flight and you can't get up and walk, something you can do is just sit in your seat and do calf raises. Keep your toes on the floor and raise your heels up and down," said Hall.
You should also stay hydrated.
"Try to avoid alcohol. Try to avoid becoming dehydrated when you fly," said Hall.
You should also know your risk factors. Birth control pills, being overweight, and smoking also increase your risk of DVT.
If you experience sudden pain and swelling in your calf or leg, experts say you should seek out medical help immediately.