What Is Excessive Blood Clotting (Hypercoagulability)?

When you get a cut or injury, your body forms blood clots to help stop the bleeding. Blood clots form when proteins in your blood (such as fibrin, formed from fibrinogen) work with small blood cell fragments (platelets) to seal the wound. This is called coagulation, or clotting. This process helps the body form a clot when an injury occurs. This slows blood loss.

Once healing has occurred, the body usually breaks down the clot and removes it. But sometimes clots form where they aren’t needed or don’t dissolve the way they should. When that happens, clots can travel through the body and partially or completely block blood flow.

This condition is called excessive blood clotting, or hypercoagulability. Because clots can interfere with blood flow to vital organs, it can be very dangerous. Clots can form in veins or, in some cases, arteries and can travel through the bloodstream. Clots in arteries can cause heart attack, stroke, while clots in veins can travel to the lungs and cause a pulmonary embolism.

Other names for excessive blood clotting include:

• Hypercoagulable disorders or states
• Hypercoagulation
• Thromboembolic states (clots that embolize)
• Thrombophilia
• Thrombotic disorders 

Why excessive blood clotting matters

The outlook and treatment for excessive blood clotting depend on the cause of the blood clots, how severe they are and how well they can be controlled.

Blood clots can occur in veins or arteries and can lead to serious health problems.

Clots in veins

• Deep vein thrombosis (DVT): A clot in a deep vein, usually in the leg or arm, can cause pain, swelling, redness and warmth in the affected limb. Part of the clot can break loose and travel through the bloodstream.
• Pulmonary embolism (PE): If a clot travels to the lungs, it can block blood flow and reduce oxygen levels in the blood. PE is a serious and potentially life-threatening condition.
• Venous thromboembolism (VTE): DVT and PE together are known as venous thromboembolism.

Clots in arteries

• Stroke: A clot that blocks blood flow to the brain can cause brain injury, disability or death.
• Heart attack: A clot in a coronary artery can block blood flow to the heart muscle, causing damage or death of heart tissue.

With medications and ongoing care, many people with excessive blood clotting are able to manage the condition successfully.

Risk Factors for Excessive Blood Clotting

Acquired risk factors

Excessive blood clotting can be triggered by another disease or condition, including:

• Overweight and obesity
• Age 65 and older
• Pregnancy
• Immobility, such as from surgery, illness, long-haul flights or being in the hospital
• Use of birth control pills or hormone replacement therapy with estrogen
• Cancer
• Smoking
• Diabetes
• Autoimmune conditions, such as antiphospholipid syndrome, rheumatoid arthritis, systemic lupus erythematosus and inflammatory bowel disease
• Dehydration, especially when combined with immobility

Genetic risk factors

Inherited causes of excessive blood clotting are less common. They are usually related to changes in genes that affect how blood clots form or dissolve.

You are more likely to have a genetic cause of excessive blood clotting if you have:

• Family members who have had serious blood clots
• A history of repeated blood clots before age 40
• A history of unexplained miscarriages

Other conditions linked to blood clots

Some health conditions make clots more likely to form in certain parts of the body.

Conditions that can trigger excessive blood clotting in the heart and brain:

• Vasculitis causes inflammation in blood vessels and can encourage clot formation.
• Diabetes increases the risk of plaque buildup in the arteries, which can cause  blood clots.
• Heart failure is a condition in which the heart is damaged or weakened. When the heart can't pump enough blood to meet the body's needs, blood flow slows. This can cause clots to form ‒ most commonly in the leg.
• Atrial fibrillation is the most common type of arrhythmia, or irregular heartbeat. Atrial fibrillation can cause blood to pool in the upper chambers of the heart (atria) and can cause clots to form.
• Overweight and obesity refer to body weight that is greater than considered healthy. These conditions can lead to inflammation and damage the lining of the blood vessels.
• Metabolic syndrome is a group of risk factors that increases your chance of having heart disease and other health problems, including an increased risk of blood clots.

Conditions that can cause excessive blood clotting in the limbs include:

• Peripheral artery disease (PAD) is a condition in which plaque builds up in the walls of the peripheral arteries, causing narrowing of the artery’s lumen (opening) and reducing blood flow, most commonly to the pelvis and legs.
• Atherosclerosis: is a disease in which plaque (fat, cholesterol and other deposits) builds up in the wall of an artery. Plaque can grow large enough to reduce the blood flow through an artery. When a plaque becomes brittle or inflamed, it can rupture, causing a blood clot to form. A clot may further narrow the artery or completely block it.

Symptoms of Excessive Blood Clotting

Signs and symptoms depend on where a clot forms.

• Heart or lungs: Chest pain, shortness of breath or discomfort in the arms, back, neck or jaw may signal a heart attack or pulmonary embolism (PE).
• Brain: Headache, paralysis (inability to move), dizziness and trouble speaking or understanding speech, which may suggest a stroke.
• Deep veins (usually the leg): Pain, redness, warmth or swelling may point to deep vein thrombosis (DVT). 

If you have signs or symptoms of a heart attack, PE or stroke, call 911 right away. If you have signs or symptoms of DVT, call your health care professional right away. The cause of the blood clot needs to be found and treated as soon as possible.

How Excessive Blood Clotting is Diagnosed

If your health care professional suspects excessive blood clotting, they will start by learning more about your health and family history and doing a physical exam.

They may ask whether you or a close relative has had:

• Abnormal or excessive clotting
• A history of repeated blood clots before age 40
• Clots during pregnancy or while on birth control pills
• Unexplained miscarriages
• A history of excessive or unusual blood clots (such as in the veins in the liver or kidneys)

Blood work will also be reviewed. Initial tests may include a complete blood count and a platelet count. These tests don’t diagnose clotting disorders, but they can help identify conditions that may contribute to clot risk. Additional blood tests may be done if more information is needed.

How to Prevent Excessive Blood Clotting

While you can’t prevent genetic causes of excessive blood clotting, there are steps that may help lower the risk of acquired factors:

• Treating conditions that can lead to excessive blood clotting, such as diabetes or heart and vascular diseases
• Quitting smoking
• Reaching or maintaining a healthy weight
• Talking with your health care professional about non-estrogen birth control options
• Staying as active as you’re able, especially during trips five hours or longer, by moving and stretching your legs
• Taking anticoagulant medications when prescribed, such as before and after surgery 

Treatment of Excessive Blood Clotting

ETreatment depends on where a clot is located and how serious it is.

• Emergency Treatment – Blood clots can damage the body, leading to serious problems, such as stroke, heart attack, kidney failure, DVT or PE. They can also cause miscarriages, stillbirths or pregnancy-related problems. Emergency treatment to prevent these problems often involves medications called thrombolytics that can quickly break up clots. Because these medicines can increase the risk of bleeding, they’re used only in life-threatening situations.
• Routine Treatment – In a non-emergency situation, anticoagulants are used to keep existing clots from growing and to reduce the chance of new ones forming. Options may include:
  • Warfarin, taken by mouth
  • Heparin given by injection or IV
  • Direct-acting oral anticoagulants, or DOACs, such as apixaban, dabigatran, rivaroxaban or edoxaban