Blood clots are clumps that occur when blood hardens from a liquid to a solid.
- A blood clot that forms inside one of your veins or arteries is called a thrombus. A thrombus may also form in your heart.
- A thrombus that breaks loose and travels from one location in the body to another is called an embolus.
A thrombus or embolus can partly or completely block the flow of blood in a blood vessel.
- A blockage in an artery may prevent oxygen from reaching the tissues in that area. This is called ischemia. If ischemia is not treated promptly, it can lead to tissue damage or death.
- A blockage in the vein will often cause fluid buildup and swelling.
Clot; Emboli; Thrombi; Thromboembolus; Hypercoagulable state
Situations in which a blood clot is more likely to form in veins include:
- Being on long-term bed rest
- Sitting for long periods, such as in a plane or car
- During and after pregnancy
- Taking birth control pills or estrogen hormones (especially in women who smoke)
- Long-term use of an intravenous catheter
- After surgery
Blood clots are also more likely to form after an injury. People with cancer, obesity, and liver or kidney disease are also prone to blood clots.
Smoking also increases the risk of forming blood clots.
Conditions that are passed down through families (inherited) may make you more likely to form abnormal blood clots. Inherited conditions that affect clotting are:
- Factor V Leiden mutation
- Prothrombin G20210A mutation
Other rare conditions, such as protein C, protein S, and antithrombin III deficiencies.
A blood clot may block an artery or vein in the heart, affecting the:
- Heart (angina or a heart attack)
- Intestines (mesenteric ischemia or mesenteric venous thrombosis)
- Kidneys (renal vein thrombosis)
- Leg or arm arteries
- Legs (deep vein thrombosis)
- Lungs (pulmonary embolism)
- Neck or brain (stroke)
Anderson JA, Hogg KE, Weitz JI. Hypercoagulable states. In: Hoffman R, Benz EJ, Silberstein LE, et al, eds. Hematology: Basic Principles and Practice. 7th ed. Philadelphia, PA: Elsevier; 2018:chap 140.
Schafer AI. Approach to the patient with bleeding and thrombosis: hypercoagulable states. In: Goldman L, Schafer AI, eds. Goldman-Cecil Medicine. 26th ed. Philadelphia, PA: Elsevier; 2020:chap 162.
- Last reviewed on 5/27/2020
- Todd Gersten, MD, Hematology/Oncology, Florida Cancer Specialists & Research Institute, Wellington, FL. Review provided by VeriMed Healthcare Network. Also reviewed by David Zieve, MD, MHA, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.
A.D.A.M., Inc. is accredited by URAC, also known as the American Accreditation HealthCare Commission (www.urac.org). URAC's accreditation program is the first of its kind, requiring compliance with 53 standards of quality and accountability, verified by independent audit. A.D.A.M. is among the first to achieve this important distinction for online health information and services. Learn more about A.D.A.M.'s editorial process. A.D.A.M. is also a founding member of Hi-Ethics (www.hiethics.com) and subscribes to the principles of the Health on the Net Foundation (www.hon.ch).
The information provided herein should not be used during any medical emergency or for the diagnosis or treatment of any medical condition. A licensed physician should be consulted for diagnosis and treatment of any and all medical conditions. Call 911 for all medical emergencies. Links to other sites are provided for information only -- they do not constitute endorsements of those other sites. Copyright 2002 A.D.A.M., Inc. Any duplication or distribution of the information contained herein is strictly prohibited.