What is a blood clot?
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. Clots are made up of things in your bloodstream:
Platelets (cell-like blood particles)
Red blood cells
Special proteins called clotting factors
After your blood vessel heals, the blood clot isn’t needed anymore. Then your body breaks up (dissolves) the clot.
How does blood 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 blood vessel narrows to slow the flow of blood
Platelets stick to the damaged area of the blood vessel
The platelets release substances that activate the clotting factor proteins
The clotting factors form a net that traps red blood cells and more platelets
The clump of material quickly grows until it's big enough to plug the blood vessel.
Blood Clots: Plugging the Breaks
When an injury causes a blood vessel wall to break, platelets are activated. They change shape from round to spiny, stick to the broken vessel wall and each other, and begin to plug the break. They also interact with other blood proteins to form fibrin. Fibrin strands form a net that entraps more platelets and blood cells, producing a clot that plugs the break.
What can go wrong with the clotting process?
Too much clotting
Some health problems cause your body to form too many blood clots (excessive blood clotting Excessive 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:
Pulmonary embolism Pulmonary Embolism (PE) Pulmonary is a medical word that refers to the lungs. An embolism is a clump of material (usually a blood clot) moving through your bloodstream. An embolism usually gets stuck when it gets to... read more , a problem that happens when your blood carries clots from your legs, pelvis, or belly area into your lungs
Not enough clotting
Some health problems keep your body from clotting enough. Even small damage to a blood vessel may lead to serious bruising and bleeding Bruising and Bleeding Bruising or bleeding after an injury is normal. However, some people have blood clotting disorders that cause them to bruise or bleed too easily, such as after very minor injuries or even no... read more . 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.
How do doctors treat blood clots?
If your blood is clotting too much, doctors may give you:
Drugs such as aspirin that block platelets
Drugs that block your clotting factors
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).
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