Blood clots, like the one 65-year-old Secretary of State Hillary Rodham Clinton is being treated for following her recent concussion, can occur for a host of reasons. How serious a clot can be depends on where it is and why it formed. In the case of Clinton, an aide would not say where hers is located.
What Are They: Blood pools thicken into a clot after an injury or because of a heart problem, clogged arteries or other conditions. Clots can also break off and travel to another part of the body.
Where They Occur: In leg veins, also known as deep vein thrombosis, or in blood vessels in the neck, brain or lungs. Leg clots are a common risk after someone gas been bedridden. Clots are most dangerous when they travel to the lungs, a potentially life-threatening situation, or to the brain, where they can cause a stroke.
Risk Factors: High blood pressure, diabetes, birth control pills, pregnancy, stroke, recent surgery, prolonged sitting, circulation and heart problems –especially an irregular heartbeat called atrial fibrillation– raise the chances of developing a blood clot.
Treatment: Sometimes a blood thinner such as warfarin (Coumadin) is prescribed to allow the clot to dissolve by itself over time and prevent new ones from forming.
Based on reporting by The Associated Press.