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What is a blood clot?
A blood clot is mass of blood that forms when platelets, proteins, and cells in the blood stick together. When you get hurt, your body forms a blood clot to stop the bleeding. After the bleeding stops and healing takes place, your body usually breaks down and removes the blood clot. But sometimes the blood clots form where they shouldn't, your body makes too many blood clots or abnormal blood clots, or the blood clots don't break down like they should. These blood clots can be dangerous and may cause other health problems.
Blood clots can form in, or travel to, the blood vessels in the limbs, lungs, brain, heart, and kidneys. The types of problems blood clots can cause will depend on where they are:
- Deep vein thrombosis (DVT) is a blood clot in a deep vein, usually in the lower leg, thigh, or pelvis. It can block a vein and cause damage to your leg.
- A pulmonary embolism can happen when a DVT breaks off and travels through the bloodstream to the lungs. It can damage your lungs and prevent your other organs from getting enough oxygen.
- Cerebral venous sinus thrombosis (CVST) is a rare blood clot in the venous sinuses in your brain. Normally the venous sinuses drain blood from your brain. CVST blocks the blood from draining and can cause a hemorrhagic stroke.
- Blood clots in other parts of the body can cause problems such as an ischemic stroke, a heart attack, kidney problems, kidney failure, and pregnancy-related problems.
Who is at risk for blood clots?
Certain factors can raise the risk of blood clots:
- Atrial fibrillation
- Cancer and cancer treatments
- Certain genetic disorders
- Certain surgeries
- Family history of blood clots
- Overweight and obesity
- Pregnancy and giving birth
- Serious injuries
- Some medicines, including birth control pills
- Staying in one position for a long time, such as being in the hospital or taking a long car or plane ride
What are the symptoms of blood clots?
The symptoms for blood clots can be different, depending on where the blood clot is:
- In the abdomen: Abdominal pain, nausea and vomiting
- In an arm or leg: Sudden or gradual pain, swelling, tenderness, and warmth
- In the lungs: Shortness of breath, pain with deep breathing, rapid breathing, and increased heart rate
- In the brain: Trouble speaking, vision problems, seizures, weakness on one side of the body, and sudden severe headache
- In the heart: Chest pain, sweating, shortness of breath, and pain in the left arm
How are blood clots diagnosed?
Your health care provider may use many tools to diagnose blood clots:
- A physical exam
- A medical history
- Blood tests, including a D-dimer test
- Imaging tests, such as
What are the treatments for blood clots?
Treatments for blood clots depend on where the blood clot is located and how severe it is. Treatments may include
- Blood thinners
- Other medicines, including thrombolytics. Thrombolytics are medicines which dissolve blood clots. They are usually used where the blood clots are severe.
- Surgery and other procedures to remove the blood clots
Can blood clots be prevented?
You may be able to help prevent blood clots by
- Moving around as soon as possible after having been confined to your bed, such as after surgery, illness, or injury
- Getting up and moving around every few hours when you have to sit for long periods of time, for example if you are on a long flight or car trip
- Regular physical activity
- Not smoking
- Staying at a healthy weight
Some people at high risk may need to take blood thinners to prevent blood clots.
Diagnosis and Tests
- Coagulation Factor Tests (National Library of Medicine) Also in Spanish
- D-Dimer Test (National Library of Medicine) Also in Spanish
- MPV Blood Test (National Library of Medicine) Also in Spanish
- Partial Thromboplastin Time (PTT) Test (National Library of Medicine) Also in Spanish
- Protein C and Protein S Tests (National Library of Medicine) Also in Spanish
- Prothrombin Time Test and INR (PT/INR) (National Library of Medicine) Also in Spanish
- Blood Clots and Travel: What You Need to Know (Centers for Disease Control and Prevention) Also in Spanish
- Blood Thinners: Can I Still Get Blood Clots? (Mayo Foundation for Medical Education and Research) Also in Spanish
- CDC Recommends Use of Johnson & Johnson's Janssen COVID-19 Vaccine Resume (Centers for Disease Control and Prevention) Also in Spanish
- Understand Your Risk for Excessive Blood Clotting (American Heart Association)
- Antiphospholipid Syndrome (National Institute of Neurological Disorders and Stroke)
- Cerebral and Sinus Vein Thrombosis (American Heart Association)
- Cerebral Venous Sinus Thrombosis (CVST) (Johns Hopkins Medicine)
- Hypercoagulation (American Academy of Family Physicians) Also in Spanish
- Thrombophlebitis (Mayo Foundation for Medical Education and Research) Also in Spanish
- Thrombotic Thrombocytopenic Purpura (National Heart, Lung, and Blood Institute)
- What Is Antiphospholipid Antibody Syndrome? (National Heart, Lung, and Blood Institute)
- What Is Disseminated Intravascular Coagulation? (National Heart, Lung, and Blood Institute)
- Factor V Leiden thrombophilia: MedlinePlus Genetics (National Library of Medicine)
- Hereditary antithrombin deficiency: MedlinePlus Genetics (National Library of Medicine)
- Learning about Antiphospholipid Syndrome (APS) (National Human Genome Research Institute)
- Learning about Factor V Leiden Thrombophilia (National Human Genome Research Institute)
- Protein C deficiency: MedlinePlus Genetics (National Library of Medicine)
- Protein S deficiency: MedlinePlus Genetics (National Library of Medicine)
- Prothrombin thrombophilia: MedlinePlus Genetics (National Library of Medicine)
Statistics and Research
- Blood Clots Explained: Clearing Blockages in the System (National Institutes of Health) Also in Spanish
Journal Articles References and abstracts from MEDLINE/PubMed (National Library of Medicine)
- Article: Therapeutic Anticoagulation with Heparin in Critically Ill Patients with Covid-19.
- Article: Therapeutic Anticoagulation with Heparin in Noncritically Ill Patients with Covid-19.
- Article: Standard prophylactic versus intermediate dose enoxaparin in adults with severe COVID-19:...
- Blood Clots -- see more articles
- Arterial embolism (Medical Encyclopedia) Also in Spanish
- Blood clots (Medical Encyclopedia) Also in Spanish
- D-dimer test (Medical Encyclopedia) Also in Spanish
- Prothrombin time (PT) (Medical Encyclopedia) Also in Spanish
- Superficial thrombophlebitis (Medical Encyclopedia) Also in Spanish
- Thrombophlebitis (Medical Encyclopedia) Also in Spanish