Dear Dr. Roach: My brother-in-law has had blood clots in his legs twice before. Now he has another one in his calf, and tests showed several in his lungs! What causes blood clots, and how can you prevent them? M.K.E.
Answer: The body must have a robust ability to stop bleeding, which needs to be ready at any time. That ability has a cost: possible inappropriate clotting inside the body.
Most people will never have a problem with inappropriate clotting, but there are dozens of medical conditions that can increase the risk. Some of these run in families. Prolonged immobility, such as during a hospitalization or even on long plane rides, is a clear risk factor for blood clots. All types of cancer increase the risk of blood clots, as does surgery. A pregnant woman, or one taking estrogen, is at higher risk. People with some genetic conditions are at higher risk; one thats common is the factor V Leiden mutation.
While there is nothing you can do about a genetic predisposition, there is some advice that can help people who are at risk for other reasons to avoid blood clots. For those people at lower risk, here are some practical tips for avoiding them:
Stay active and avoid sitting for long periods of time. Get up once an hour, even if only for a minute.
If you cant move for example, if the seat belt sign never gets turned off on a long plane ride at least move your feet and work the muscles of your legs.
Drink adequate water during travel.
People who have already had a deep vein thrombosis, a blood clot deep in the leg veins, should get specific medical advice about preventing another one, including possibly using medication.
