8 Risk Factors for Blood Clots

Blood clots (also called thrombi) are a collection of blood cells that block blood flow in the veins or the arteries.  This lack of blood flow can cause significant damage especially if a piece of the thrombus breaks off and travels to the lungs causing a pulmonary embolus.  Let's discuss some things that may put you at higher risk of developing clots.  

Other family members have clots

Blood Clot
Blood Clot. BSIP/UIG//Getty Images

Do other members of your family have blood clots, pulmonary emboli, or stroke?  There are inherited conditions (like factor V Leiden and prothrombin mutation) that increase your risk of developing a blood clot, particularly in certain situations (pregnancy, after orthopedic surgery, after long plane flights, etc.)?  It is important to know your family history so your physician can discuss your risk.  

You need a central line

A central line or central venous catheter is a tube that is placed in a large vein draw lab test or administer medications.  They may be called Hickman line, port-a-cath, or PICC (among others).  The catheter may irritate the lining of the blood vessels or alter the blood flow near it triggering the coagulation system to form a clot. 

You aren't able to move for long periods of time

If you are on bed-rest, have prolonged hospitalization, or paralysis can put you at risk for blood clots particularly in the legs.  Contracting the muscles in the legs helps bring the blood back to the heart.  When this doesn’t happen, the blood flow is reduced and may increase your risk for clot formation.  In some people this may happen after car rides or flights (generally > 4 hours) when you are seated for long periods of time. 

You are pregnant

Pregnant Woman in Window
Pregnant Woman in Window. JGI/Jamie Grill/Blend Images/Getty Images

Pregnancy alters the coagulation (bleeding & clotting system) proteins putting pregnant women at increased risk for clot formation.  Also the developing fetus puts pressure on the blood vessels of the pelvis, reducing blood flow from the legs, another risk factor for blood clots.

You need treatment for cancer

Chemotherapy. Lara B Arnold/Moment/Getty Images

Some cancers (particularly pancreatic, lung, multiple myeloma, blood cancers) and chemotherapies (medications to treat cancer) alter the coagulation system to be pro-clot formation.  Most patients receiving chemotherapy also have a central venous catheter giving them 2 risk factors.

You are on birth control or hormone replacement therapy

Hormonal birth control and hormone replacement therapy put women at higher risk of developing a clot.  Estrogen and progesterone, the 2 hormones that can be found in these medications, alter your coagulation system.  Also men who receive testosterone are at risk.  It is important to talk to your physician about this risk, especially if you have other risk factors, before starting these medications.  

You need a heart cath

Cardiac Catheterization
Cardiac Catheterization. Jeff Cadge/The Image Bank/Getty Images

In cardiac (heart) catheterization a tube placed in a vein or artery typically in the leg is used to access the heart for diagnostic tests as well as treatments.  The catheter can cause irritation to the lining of the blood vessel trigging formation of a clot.  This is more common in infants and young children who need this procedure.  

You need surgery

Surgery increases your risk for clot in multiple ways.  If blood vessels (arteries or veins) are damaged during the surgery, you may be at risk for a clot.  Also if you have a large surgery requiring you to stay in bed for a long period of time, you may be at risk.  Your surgeon might use  

Know Your Risks

Just because you have one of these risks, does not mean you will develop a blood clot. Most of the time it is a combination of these risks that ends up in a clot forming. Talk to your health care provider if you have concerns.

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