Blood Clotting Disorders: Causes, Symptoms, and Treatment Explained
Updated: 3 days ago
Medically reviewed by Dr. Baraa Alnahhal, MD. Last reviewed October 13, 2026. This content is for educational purposes and is not medical advice.
Quick Answer
Blood clotting disorders are conditions that make blood clot too easily, raising the risk of clots in veins or arteries [1]. Factor V Leiden and prothrombin gene mutation are common inherited forms [1]. Treatment uses anticoagulants such as warfarin, heparin and direct oral anticoagulants [1], and most people manage well. Chest pain with trouble breathing is an emergency, so call 911.
What the research says
Inherited clotting defects raise the odds of a venous clot by different amounts. A meta-analysis of 107 publications covering 107,130 adults (21,560 with a venous clot) found the highest odds with two copies of Factor V Leiden (odds ratio 5.58, 95% CI 4.61 to 6.74) and lower odds with one copy of Factor V Leiden (odds ratio 2.97, 95% CI 2.41 to 3.67) or the prothrombin mutation (odds ratio 2.21, 95% CI 1.70 to 2.87). Protein C, protein S, and antithrombin deficiency fell in between (odds ratios 3.23, 3.01, and 4.01) (Alnor et al., Ann Hematol, 2024) [6].
Newer blood thinners work about as well as warfarin, with less major bleeding. A review of lower-leg and thigh vein clots found that direct oral anticoagulants (rivaroxaban, apixaban, dabigatran, and edoxaban) were noninferior to warfarin for recurrent clots or clot-related death (2.0% vs 2.2%), and major bleeding occurred in 1.1% of patients on direct oral anticoagulants versus 1.8% on warfarin (Chopard et al., JAMA, 2020) [7].
Cancer type changes clot risk a lot. A comprehensive review reports that venous clots occur at about 1 to 2 per 1,000 person-years in Western countries, with the highest incidence in pancreatic, liver, and non-small cell lung cancer (more than 70 per 1,000 person-years) and the lowest in breast cancer, melanoma, and prostate cancer (fewer than 20 per 1,000 person-years) (Pastori et al., Int J Mol Sci, 2023) [8].
What Is a Blood Clotting Disorder?
A blood clotting disorder makes your blood form clots too easily. Doctors may call it a hypercoagulable state or thrombophilia. These conditions can be inherited from your parents or develop later in life [1] [5]. Even if you have one, you may never develop a dangerous clot such as a stroke. Medicine can keep your blood from clotting too much.
Your body clots on purpose. When you get hurt, clotting proteins made by your liver stick to platelets in your blood to form a clot. This normal clotting — called coagulation — stops a cut from bleeding and starts healing [1]. Problems happen when clotting goes too far.
Is a Blood Clotting Disorder Dangerous?
Yes, especially without treatment. People with coagulation disorders have a higher risk of forming clots in their arteries (vessels that carry blood away from the heart) and veins (vessels that carry blood back to the heart) [1]. A clot inside a blood vessel is also called a thrombus or an embolus.
Where the clot forms | What it can cause |
Veins (leg, pelvis, arm, liver, intestines, kidneys) | Deep vein thrombosis (DVT), a clot that can travel |
Lungs (a traveling vein clot) | Pulmonary embolism (PE) |
Arteries (brain, heart, legs) | Stroke, heart attack, severe leg pain, difficulty walking, possible loss of an arm or leg |
A blood clotting disorder can also raise the risk of miscarriage, especially with antiphospholipid syndrome [1]. During pregnancy, higher blood volume and pressure make anyone about five times more likely to develop a blood clot [1] — even without a clotting disorder.
What Are the Symptoms?
Blood clotting disorder symptoms depend on where a clot forms in the body. Watch for these warning signs:
Possible location of a clot | Symptoms to watch for |
Deep vein thrombosis (DVT) | Swelling, tenderness, and pain in your leg |
Pulmonary embolism (PE) | Chest pain with shortness of breath |
Arteries of the heart | Heart attack symptoms |
Arteries of the brain | Stroke symptoms |
Emergency: Call 911 if you have chest pain and difficulty breathing, which can signal a pulmonary embolism. Heart attack and stroke symptoms also need emergency treatment.
What Causes a Blood Clotting Disorder?
Hypercoagulable states are usually genetic (inherited from your parents) or acquired (caused by surgery, trauma, medications, or a medical condition) [1] [2].
Common inherited types
Inherited condition | What it involves |
Factor V Leiden | The most common inherited clotting defect |
Prothrombin gene mutation (G20210A) | A gene change that increases clot risk |
Antithrombin, protein C, or protein S deficiency | Low levels of natural proteins that prevent clotting |
Elevated or dysfunctional fibrinogen | Too much, or faulty, clotting protein |
Elevated factor VIII (and factors IX, XI) | Higher-than-normal clotting factors |
Abnormal fibrinolytic system | Faulty clot-breakdown process |
About 3% to 8% of people with European ancestry carry one copy of the Factor V Leiden mutation, and about 1 in 5,000 has two copies [3]. About 1 in 50 white people in America and Europe carry the prothrombin mutation. Both mutations are less common in other populations.
Common acquired causes
Cancer is one of the most common causes of acquired clotting disorders [1]. Other causes include recent trauma or surgery, central venous catheter placement, obesity, pregnancy, estrogen use (including birth control pills and hormone replacement therapy), and long periods of not moving — such as bed rest or long plane rides. Heart attack, heart failure, and stroke can also raise risk by limiting activity [1].
Less common causes include heparin-induced thrombocytopenia, autoimmune disorders, a previous DVT or pulmonary embolism, certain bone marrow disorders such as polycythemia vera, inflammatory bowel disease, folate or other B vitamin deficiency, HIV, sepsis, and nephrotic syndrome [1].
Who Should Get Tested?
Genetic clotting disorder testing suits only some people, since having a risk factor does not automatically mean you have such a disorder. Your healthcare provider will review your personal and family medical history before ordering tests. You may be a candidate for screening if you have any of the following:
Screening trigger | Why it matters |
Family history of abnormal clotting | Inherited forms run in families |
Clotting at a young age (under 50) | Unusual for a first-time clot |
Clots in unusual locations | Arm veins, liver, intestines, kidney, or brain |
Clots without a clear cause | May point to a hidden disorder |
Clots that keep returning | Recurrence suggests an underlying tendency |
Frequent miscarriages | Linked to antiphospholipid syndrome |
Stroke at a young age | Rare in younger people |
Tests are best done when you are not having an active clotting event, by a specialized coagulation laboratory, and interpreted by a specialist in coagulation, vascular medicine, or hematology [1].
What Tests Diagnose a Blood Clotting Disorder?
Blood tests help your provider understand your condition. General clotting tests include PT-INR (prothrombin time, used to monitor warfarin and measure how fast your blood clots), aPTT (activated partial thromboplastin time, which measures clotting time and monitors heparin), a fibrinogen test, and a complete blood count (CBC) [1].
Test type | Examples |
General clotting tests | PT-INR, aPTT, fibrinogen, CBC |
Inherited disorder tests | Genetic tests for Factor V Leiden, activated protein C resistance, prothrombin mutation; antithrombin, protein C, and protein S activity; homocysteine |
Acquired disorder tests | Antiphospholipid antibody panel; heparin antibodies |
Testing helps identify your risk of future clots, determine the right treatment and how long to take it, and find relatives who may be at risk even without symptoms [1].
How Is a Blood Clotting Disorder Treated?
In most cases, you only need treatment when a clot actually develops in a vein or artery [1]. The mainstay of treatment is anticoagulants — medicines that decrease your blood's ability to clot and prevent new clots from forming.
Anticoagulant | How it is given |
Aspirin | Tablet |
Warfarin (Coumadin, Jantoven) | Tablet you swallow |
Heparin | IV or injection, given in the hospital |
Low-molecular weight heparin | Injection once or twice daily, can take at home |
Fondaparinux | Injection |
Direct oral anticoagulants (rivaroxaban, apixaban, dabigatran) | Tablets |
Your provider will discuss the benefits and risks of each option, then decide which medicine you need, for how long, and what monitoring you need. Do not take warfarin if you are pregnant or planning pregnancy — ask your provider about switching to a different anticoagulant, especially in the first trimester and before delivery [1].
Side effects of anticoagulants can include bad headaches, dizziness, and heavy bleeding [1].
What can't I eat while taking warfarin?
Foods high in vitamin K can change how warfarin works. These include Brussels sprouts, spinach, and broccoli [1]. Ask your provider about specific dietary guidelines for your situation.
Self-care while taking warfarin
Wear a medical identification bracelet so emergency teams know you take anticoagulants. Over-the-counter medicines can affect how anticoagulants work, so never start a new medication without talking to your provider first. You will also need frequent blood tests to check how well warfarin is working, and your dose may be adjusted based on the results [1].
How Can I Prevent a Blood Clot?
You cannot prevent an inherited clotting disorder — you are born with it. But having one does not guarantee a clot will form. For acquired risk factors, practical steps include finding non-estrogen alternatives to birth control pills or hormone replacement therapy, staying at a healthy weight, making sure you get the vitamins you need, and getting up to walk around — especially during long flights and after surgery [1].
What Is the Outlook?
Blood clotting disorders can be managed with medicine and regular follow-up appointments [1]. If you plan to have surgery or become pregnant, talk with your provider ahead of time about staying safe during those higher-risk periods.
Inherited forms last for life, though a lifelong diagnosis does not mean you will definitely get a blood clot — certain situations can add risk on top of what you already have. Many acquired disorders go away once the cause resolves [1]. For example, once you are up and moving again after a long flight, your clot risk drops back down.
When Should You See a Doctor?
Call your provider if you take warfarin and experience heavy or unusual bleeding or bruising, or if you suspect deep vein thrombosis [1]. Call 911 for chest pain with difficulty breathing (possible pulmonary embolism), or for any heart attack or stroke symptoms. Good questions to ask your doctor include: which type of blood clotting disorder do I have, what is the best treatment for me, and is there a support group I can join?
Conclusion
A blood clotting disorder means your body forms clots too easily — through inherited gene changes like Factor V Leiden or acquired factors like cancer, surgery, pregnancy, or estrogen use. While these conditions raise the risk of deep vein thrombosis, pulmonary embolism, stroke, and heart attack, most people manage them successfully with anticoagulant medicine, smart habits like staying active on long trips, and regular follow-up care. If you notice leg swelling and pain, chest pain, or trouble breathing, do not wait — seek medical care right away.
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Frequently Asked Questions
What is a blood clotting disorder?
It is a condition that makes your blood form clots too easily, also called a hypercoagulable state or thrombophilia. It can be inherited or acquired later in life.
Is thrombophilia dangerous?
It can be, especially without treatment, because it raises the risk of clots in your veins and arteries. These clots can cause deep vein thrombosis, pulmonary embolism, stroke, or heart attack.
What are the most common inherited blood clotting disorders?
Factor V Leiden and the prothrombin gene mutation (G20210A) are the most commonly identified genetic defects that increase clot risk.
How common is Factor V Leiden?
About 3% to 8% of people with European ancestry carry one copy, and about 1 in 5,000 people has two copies. It is less common in other populations.
What causes acquired blood clotting disorders?
Common causes include cancer, surgery or trauma, pregnancy, obesity, estrogen use (birth control pills, hormone therapy), and long periods of immobility such as bed rest or long flights.
What are the symptoms of a blood clot in the leg?
Swelling, tenderness, and pain in the leg can signal deep vein thrombosis (DVT).
When should I call 911?
Call 911 if you have chest pain with difficulty breathing, which can signal a pulmonary embolism. Heart attack and stroke symptoms also require emergency care.
Can a blood clotting disorder cause miscarriage?
Yes, especially with conditions like antiphospholipid syndrome. Pregnancy itself raises blood volume and pressure, making anyone about five times more likely to form a clot.
How is a blood clotting disorder diagnosed?
Through blood tests such as PT-INR, aPTT, fibrinogen, CBC, and genetic or antibody tests — interpreted by a coagulation specialist, ideally when you are not having an active clot.
Who should get tested for a clotting disorder?
People with a family history of abnormal clotting, clots before age 50, clots in unusual locations, repeated clots, unexplained clots, frequent miscarriages, or stroke at a young age.
How are blood clotting disorders treated?
Most often with anticoagulant medicines such as warfarin, heparin, low-molecular weight heparin, fondaparinux, or direct oral anticoagulants like rivaroxaban, apixaban, and dabigatran. Treatment is usually only needed when a clot forms.
Can I take warfarin while pregnant?
No — you should not take warfarin if you are pregnant or planning pregnancy. Ask your provider about switching to a different anticoagulant, especially in the first trimester and before delivery.
What foods should I avoid on warfarin?
Foods high in vitamin K can change how warfarin works, including Brussels sprouts, spinach, and broccoli. Ask your provider for guidance specific to you.
Do blood clotting disorders go away?
Inherited forms are lifelong, though they do not guarantee a clot will form. Many acquired disorders resolve when the underlying cause resolves, such as moving again after a long flight.
How can I lower my risk of an acquired blood clotting disorder?
Stay at a healthy weight, get the vitamins you need, consider non-estrogen alternatives to birth control or hormone therapy, and get up and walk regularly — especially on long flights and after surgery.
Related Reading
Partial Thromboplastin Time (PTT) Test: Normal Range and Results explains the blood clotting test used to monitor heparin and check bleeding problems.
Factor V Leiden: An Inherited Blood Clot Risk Explained — Symptoms, Causes, and Treatment: the most common inherited clotting defect in depth.
Pulmonary Embolism Guide: Symptoms, Causes, Diagnosis, and Treatment: when a vein clot travels to the lungs.
Antiphospholipid Syndrome: Symptoms, Causes, Treatment & Complete Guide: a well-known acquired clotting disorder.
Prothrombin Time (PT/INR) Test: Normal Ranges, Warfarin Targets and Results explains the clotting test used to monitor warfarin and liver function.
References
Cleveland Clinic. Blood Clotting Disorders (Hypercoagulable States). Cleveland Clinic. Updated July 1, 2022. https://my.clevelandclinic.org/health/diseases/16788-blood-clotting-disorders-hypercoagulable-states
American Heart Association. What Is Excessive Blood Clotting (Hypercoagulability)? American Heart Association. Reviewed February 25, 2026. https://www.heart.org/en/health-topics/venous-thromboembolism/what-is-excessive-blood-clotting-hypercoagulation
MedlinePlus. Factor V Leiden thrombophilia. MedlinePlus Genetics. Updated August 10, 2023. https://medlineplus.gov/genetics/condition/factor-v-leiden-thrombophilia/
National Blood Clot Alliance. Direct Oral Anticoagulants (DOACs). National Blood Clot Alliance. Accessed October 14, 2026. https://www.stoptheclot.org/about-clots/blood-clot-treatment/direct-oral-anticoagulants/
National Heart, Lung, and Blood Institute. What Are Blood Clotting Disorders? NHLBI, NIH. Updated March 24, 2022. https://www.nhlbi.nih.gov/health/clotting-disorders
Alnor AB, et al. Venous thromboembolism risk in adults with hereditary thrombophilia: a systematic review and meta-analysis. Ann Hematol. 2024;103(10):4285-4294. PMID 39167180. https://doi.org/10.1007/s00277-024-05926-2
Chopard R, et al. Diagnosis and Treatment of Lower Extremity Venous Thromboembolism: A Review. JAMA. 2020;324(17):1765-1776. PMID 33141212. https://doi.org/10.1001/jama.2020.17272
Pastori D, et al. A Comprehensive Review of Risk Factors for Venous Thromboembolism: From Epidemiology to Pathophysiology. Int J Mol Sci. 2023;24(4):3169. PMID 36834580. https://doi.org/10.3390/ijms24043169
Medical disclaimer
This article is for general informational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always consult a qualified healthcare provider about any medical condition, and call 911 or seek emergency care for chest pain, difficulty breathing, or stroke symptoms.
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