Hypercoagulable Disorders (Hypercoagulable States)

How blood can become hypercoagulable

Clotting depends on three factors, known as Virchow's triad:

1. Slow blood flow: from immobility, long travel, paralysis or a cast
2. Damage to the vessel wall: from surgery, injury, catheters or inflammation
3. Changes in the blood itself: more clotting proteins, fewer natural anticoagulants, or more platelets or red cells

Hypercoagulable disorders mainly affect the third factor. A clot usually needs more than one factor together. For example, a woman with factor V Leiden may never clot until she is also pregnant or taking estrogen.

Acquired hypercoagulable states

These are far more common than inherited causes.

Inherited hypercoagulable disorders

Inherited clotting disorders are known as inherited thrombophilias. They are covered in more depth on our thrombophilia page.

• Factor V Leiden: the most common inherited cause in people of European ancestry. Factor V resists being switched off by protein C.
• Prothrombin gene mutation (G20210A): raises prothrombin levels.
• Protein C, protein S and antithrombin deficiencies: less common but higher risk, because the body's own anticoagulants are low.
• High homocysteine: a weak risk factor, now considered of limited importance.

Signs of a blood clot

Hypercoagulable disorders cause no symptoms until a clot forms. Know the signs:

• Deep vein thrombosis (DVT): swelling, pain, warmth or redness in one leg, usually the calf
• Pulmonary embolism: sudden breathlessness, sharp chest pain on breathing, a fast heart rate, coughing blood
• Arterial clot: stroke symptoms, or a cold, painful, pale limb
• Cerebral venous thrombosis: severe headache, seizures, vision changes
• Abdominal vein clot: belly pain, swelling and vomiting
• Pregnancy complications: recurrent miscarriage, stillbirth, severe preeclampsia or poor fetal growth, especially in antiphospholipid syndrome

Who should be tested

Testing is not recommended for everyone with a clot. A clot caused by a major temporary trigger, such as surgery, is usually treated the same whatever the test shows. Testing is more useful when:

• a clot happened with no trigger or with only a minor trigger, at a young age (under about 50)
• clots keep coming back
• clots occur in unusual places, such as the brain, liver or gut veins
• there is a strong family history of clots
• a woman with a relative with a known inherited thrombophilia is considering estrogen or pregnancy
• there are features of antiphospholipid syndrome, such as pregnancy loss

What the tests include

• Factor V Leiden and prothrombin gene tests (DNA tests, accurate any time)
• Protein C, protein S and antithrombin levels
• Antiphospholipid antibodies: lupus anticoagulant, anticardiolipin and anti-beta-2 glycoprotein I, repeated after 12 weeks to confirm
• Blood count, and tests for cancer or PNH when the picture suggests them

Timing matters. Protein C, S and antithrombin levels are lowered by an acute clot, pregnancy, estrogen and anticoagulants such as warfarin. Testing during these times can give false results, so many tests are done weeks or months later.

Treatment

Treating a clot

• Anticoagulants: direct oral anticoagulants (such as apixaban or rivaroxaban), low-molecular-weight heparin or warfarin. Most clots are treated for at least 3 months.
• Antiphospholipid syndrome: warfarin is preferred over direct oral anticoagulants, especially for high-risk antibody patterns or arterial clots.
• Cancer-associated clots: direct oral anticoagulants or low-molecular-weight heparin, often while the cancer is active.
• Heparin-induced thrombocytopenia: stop all heparin and switch to a non-heparin anticoagulant.

Long-term decisions

Whether to continue anticoagulation indefinitely depends on whether the first clot had a trigger, the bleeding risk, and the specific disorder. An unprovoked clot often leads to long-term treatment, regardless of test results.

Preventing clots

• Preventive heparin or other anticoagulants after surgery, during hospital stays, and in pregnancy and after birth for people at higher risk
• Avoiding estrogen-containing contraception if you have a significant thrombophilia or previous clot; progestin-only methods or IUDs are usually safer
• Moving and flexing your calves every hour or two on long flights or car trips, and staying hydrated
• Maintaining a healthy weight and not smoking

Frequently asked questions

What is a hypercoagulable state?

It is any condition that makes blood clot more easily than normal. It can be inherited, such as factor V Leiden, or acquired, such as cancer, pregnancy, estrogen, surgery or antiphospholipid syndrome. It raises the risk of clots in veins and sometimes arteries.

What is the most common cause of a hypercoagulable state?

Acquired causes are the most common, particularly surgery, immobility, cancer, pregnancy and estrogen use. Among inherited causes, factor V Leiden is the most common in people of European ancestry, followed by the prothrombin gene mutation.

Should I be tested for a clotting disorder after a blood clot?

Not always. If the clot had a clear major trigger, such as surgery, testing rarely changes treatment. Testing is more useful for unprovoked clots at a young age, recurrent or unusual-site clots, a strong family history, or pregnancy loss. Your doctor will decide which tests are worth doing and when.

Can I take birth control pills with a clotting disorder?

Estrogen-containing pills, patches and rings raise clot risk and are usually avoided in people with a significant clotting disorder or past clot. Progestin-only pills, hormonal IUDs, copper IUDs and implants are generally safer options. Discuss this with your doctor.

Is a hypercoagulable state curable?

Inherited thrombophilias are lifelong, but many people never have a clot. Acquired states often improve when the cause is removed, for example after pregnancy, stopping estrogen or treating cancer. Antiphospholipid syndrome is usually long-term and often needs ongoing anticoagulation.