These are clumps of blood that form when blood cells stick together. Some types of clots are helpful. For example, when you're cut, your blood forms a clot to seal the wound. But sometimes, blood clots can form inside your arteries or veins for other reasons. They can clog your blood vessels. This can be life-threatening.
One kind of dangerous clot is called a "deep vein thrombosis." It forms in a deep vein, often in the leg. It could be trapped there, causing pain and swelling. Or, it could break loose and travel. A blood clot that travels to your lungs can cause a pulmonary embolism. Clots that travel to your heart or brain can cause heart attack or stroke.
Some factors raise your risk. Blood clots are more common in older people, in people who are obese, and in smokers. They are more common in pregnant women. They can form if you sit for a long time, or if you are confined to a bed. Blood clots can be linked to certain medications, and to certain diseases and conditions. They can result from injury, and from some surgeries. Ask your doctor for a full list of risk factors.
If you are at risk for blood clots, you may need medications to prevent them. And, changes in your lifestyle may lower your risk. Your doctor will create a plan that's right for you.