Why is Traveling Associated with Causing Blood Clots?

By Jill Buterbaugh, RN, MSN, CRNP, FNP-BC

When traveling you are often sitting in one position for long periods of time without having the ability to walk or stretch.  Blood returning to the heart from your legs depends on the calf muscle to pump it back and a properly functioning venous system.  Blood return is sometimes restricted due to the bend in your knees and hips.  Obviously, the longer the trip, the higher the risk for developing a blood clot.  Trips greater than 8 hours are associated with higher rates of blood clots developing.

During travel people tend to drink higher amounts of caffeinated beverages and less water resulting in some level of dehydration.  Caffeine pulls fluids from your body, similar to a mild fluid pill would.  Altitude changes in air travel normally causes mild dehydration that you are not even aware of so dehydration is even greater with less water and high caffeine intake.  This can increase the thickness of the blood making it more prone to develop a blood clot.

Air travel also causes physiologic changes to the blood even though air plane cabins are pressurized, the pressure is not adjusted to sea level it is adjusted to a higher altitude.  The higher the altitude, the lower the oxygen level is in the blood. The body’s system of checks and balances causes a reflex trigger for the body to produce more platelets in the blood and platelets are a clotting component.  Blood can clot in as little as 30 seconds in a normal person.

Sitting for long periods of time also can obstruct the lymphatic system causing fluid retention in the legs. Even people without a history of fluid retention tend to notice this change.  Increased fluid in the extremities will increase the difficulty of getting the blood back to the heart because of tissue pressure on the veins.

It is difficult to determine how many people develop blood clots with travel because small clots that do not completely block the vein may not cause symptoms and the body can dissolve and reabsorb it.  In more serious cases, clots can form that completely block a major vein or even break off and travel to the heart, lung or brain causing serious illness or death.

Symptoms of blood clots in the legs include:

  • Swelling of the leg, ankle or calf
  • Pain in the calf when you flex your foot
  • Redness or discoloration
  • Increased warmth of the skin

There are many different factors that determine the risk of blood clots.  Those at higher risk for developing blood clots include:

  • People on hormone therapy or oral contraceptives
  • Pregnant women
  • People with cancer
  • Having recent surgery
  • Older people
  • People who are overweight
  • People who have had blood clots in the past
  • People who have genetic blood clotting disorders


There are things you can do to prevent blood clots when traveling.  If traveling by vehicle, plan to stop and stretch.  Walking for a few minutes every couple of hours is helpful.  If traveling by bus, train or plane where it is difficult to walk and move around, shifting or changing position in your seat, doing toe raises, flexing and pointing your toes can all help to increase the blood flow back to the heart.  Wear compression stockings which are designed to increase venous return.  Avoid tight fitting clothes that can restrict blood flow and try not to cross your legs.  Make sure to drink enough water and avoid excessive amounts of caffeine.  Make sure to take all your prescribed medications as directed.

Be sure to talk to your primary care provider if you are planning long travel and be aware of your risks.  If you suspect you may have developed a blood clot, it is very important to be evaluated and treated immediately.

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