A blood clot is a clump of material that your body makes to plug up a bleeding blood vessel. Blood clots look like dark purple jelly. They're made up of things in your bloodstream:
After your blood vessel heals, the blood clot isn’t needed anymore. Then your body breaks up (dissolves) the clot.
Platelets, red blood cells, and clotting factors circulate in your bloodstream. That way, they can be right there when a blood vessel gets cut or damaged. When a blood vessel is cut, a blood clot forms:
The clump of material quickly grows until it's big enough to plug the blood vessel.
Blood Clots: Plugging the Breaks
Some health problems cause your body to form too many blood clots (excessive blood clotting). Your clotting factors may be overactive. Or there may be a problem with your clot-dissolving system.
Too much clotting can lead to other problems such as:
Some health problems keep your body from clotting enough. Even small damage to a blood vessel may lead to serious bruising and bleeding. You may not have enough platelets, or they may not work properly. Or you might not have enough clotting factors. Some medicines affect your ability to form clots.
If your blood is clotting too much, doctors may give you:
Drugs that block your clotting factors are sometimes called "blood thinners."
If you have a dangerous blood clot in your brain or heart, doctors may give you a clot-dissolving drug. Clot-dissolving drugs can also dissolve helpful blood clots, so you may start bleeding (but this is rare).