Blood Clots

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Basics

• Summary
• Start Here
• Diagnosis and Tests
• Treatments and Therapies

Learn More

• Related Issues
• Specifics
• Genetics

See, Play and Learn

• Videos and Tutorials

Research

• Clinical Trials
• Journal Articles

Resources

• Find an Expert

For You

• Children
• Women
• Patient Handouts

Summary

Normally, if 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 clot. But some people get too many clots or their blood clots abnormally. Many conditions can cause the blood to clot too much or prevent blood clots from dissolving properly.

Risk factors for excessive blood clotting include

• Certain genetic disorders
• Atherosclerosis
• Diabetes
• Atrial fibrillation
• Overweight, obesity, and metabolic syndrome
• Some medicines
• Smoking
• Staying in one position for a long time, such as being in the hospital or taking a long car or plane ride
• Cancer and cancer treatments

Blood clots can form in, or travel to, the blood vessels in the brain, heart, kidneys, lungs, and limbs. A clot in the veins deep in the limbs is called deep vein thrombosis (DVT). DVT usually affects the deep veins of the legs. If a blood clot in a deep vein breaks off and travels through the bloodstream to the lungs and blocks blood flow, it is called a pulmonary embolism. Other complications of blood clots include stroke, heart attack, kidney problems, kidney failure, and pregnancy-related problems. Treatments for blood clots include blood thinners and other medicines.

Start Here

• Blood Clots (American Society of Hematology)
• Blood Clots (Mayo Foundation for Medical Education and Research)
• Blood Clots (Radiological Society of North America) Also in Spanish
• How Blood Clots (Merck & Co., Inc.) Also in Spanish

Diagnosis and Tests

• Antithrombin Test (American Association for Clinical Chemistry)
• Coagulation Factor Tests (National Library of Medicine) Also in Spanish
• D-Dimer Test (National Library of Medicine) Also in Spanish
• Factor V Leiden Mutation and PT 20210 Mutation Test (American Association for Clinical Chemistry)
• Fibrinogen Test (American Association for Clinical Chemistry)
• 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
• Thrombin Time (American Association for Clinical Chemistry)

Treatments and Therapies

• Blood Thinners: MedlinePlus Health Topic (National Library of Medicine) Also in Spanish
• Catheter-Directed Thrombolysis (Radiological Society of North America) Also in Spanish

Related Issues

• 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
• Understand Your Risk for Excessive Blood Clotting (American Heart Association)

Specifics

• Antiphospholipid Syndrome (National Institute of Neurological Disorders and Stroke)
• Cerebral and Sinus Vein Thrombosis (American Heart Association)
• 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)

Genetics

• 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)

Videos and Tutorials

• Blood clotting (Medical Encyclopedia) Also in Spanish

Clinical Trials

• ClinicalTrials.gov: Thrombophlebitis (National Institutes of Health)
• ClinicalTrials.gov: Thrombosis (National Institutes of Health)
• ClinicalTrials.gov: Venous Thrombosis (National Institutes of Health)

Journal Articles References and abstracts from MEDLINE/PubMed (National Library of Medicine)

• Article: Inflammation After Surgical Trauma: Bleeding or Clotting?
• Article: Hypercoagulable viscoelastic blood clot characteristics in critically ill coronavirus disease 2019...
• Article: COVID-19 as a Blood Clotting Disorder Masquerading as a Respiratory Illness:...
• Blood Clots -- see more articles

Find an Expert

• Centers for Disease Control and Prevention Also in Spanish
• Find a Hematologist (American Society of Hematology)
• National Heart, Lung, and Blood Institute

Children

• Blood (For Parents) (Nemours Foundation) Also in Spanish

Women

• Postpartum Blood Clots (Merck & Co., Inc.) Also in Spanish

Patient Handouts

• 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