What Is a Prothrombin Gene Mutation?

If you have a prothrombin gene mutation, your body is more likely to make blood clots. That has some serious health risks, but there are steps you and your doctor can take to help prevent that from happening.

Your body needs to be able to make blood clots. They help heal cuts, for example. Clotting requires a protein called prothrombin. If you have a prothrombin gene mutation, your body makes too much of it.

Without treatment, there’s a chance that could lead to problems such as a deep vein thrombosis (DVT), a clot in the deep veins of your arms or legs. A DVT can block blood flow, and it can break off and travel to your lungs as a pulmonary embolism, which is life-threatening.

Still, the mutation isn’t common. And even if you have it, you might never get a DVT. It’s all about managing the risk.


People who have this mutation are born with it. One or both of your parents passed it on to you.

If only one of your parents had this genetic mutation, you’re two to three times more likely to have a DVT than someone without it. If both parents had it, which is rare, your risk rises even more.

Even so, most people who have the mutation won’t ever get a DVT.


It’s only when you get a dangerous clot that you might notice that something is off.

With a DVT, you may have symptoms like these in your arm or leg:

  • Changes in skin color, such as more red or purple than usual
  • Heaviness, tenderness, or throbbing
  • Pain that feels like a cramp or charley horse
  • Skin that’s warm to the touch
  • Swelling
  • Veins that look larger than usual

With a pulmonary embolism, you may have:

What Women Should Know

Hormone replacement therapy and birth control pills, especially those with estrogen, can add to your risk for a DVT. So if you know you have a prothrombin gene mutation, make sure your doctor knows that before you start such treatments.

Also, most women who have this mutation have normal pregnancies. But pregnancy can make you more likely to get clots, so it’s something to discuss with your doctor. You may also be slightly more likely to have:


When Would I Need to Get Tested?

Your doctor might suggest it if you have:

  • Ever had a DVT, pulmonary embolism, or other clots
  • Had a heart attack or stroke at a young age
  • Had a miscarriage or stillbirth
  • Clots run in your family

It’s a genetic test, and you'll give a blood sample that gets sent to a lab. You will likely get results in 5-7 days.


Since there’s no cure, the goal is to lower your chance of having risky blood clots while still letting your body make the clots that it truly needs.

If you’ve never had a dangerous clot, you likely won’t need any treatment. You’ll just need to know, and watch for, DVT symptoms. If you are having surgery, which raises your risk for blood clots, make sure your doctors know.

If you do need treatment, you’ll take a blood-thinning drug to help prevent clots from forming. Doctors call these medicines anticoagulants.

Lifestyle Changes

You also lower your risk for blood clots when you:

Make exercise a habit. It can help clear clots you already have and prevent new ones from forming.

Quit smoking . Just on its own, smoking makes you more likely to get a blood clot.

Stay at a healthy weight. When you carry too many extra pounds, you boost your odds of blood flow problems and insulin issues like diabetes. Both can turn up your clot risk.

Don’t sit too long. When you sit still for hours at a time -- like on a long car or plane ride, or even while working at a desk or binge-watching on your couch -- it slows your blood flow down and makes clots more likely. Take a break at least every 2 hours or so and walk around for a few minutes.

WebMD Medical Reference Reviewed by James Beckerman, MD, FACC on January 15, 2020



Children’s Hospital Colorado: “Prothrombin Mutation G20210 and Blood Clotting.”

Genetics Home Reference: “Prothrombin Thrombophilia.”

University of Iowa Health Care: “Prothrombin Gene Mutation.”

American Heart Association and American Stroke Association, Circulation: “Prothrombin 20210 Mutation (Factor II Mutation).”

University of Iowa Hospitals and Clinics: “May-Thurner Syndrome.”

Cleveland Clinic: “May-Thurner Syndrome.”

National Blood Clot Alliance: “A Genetic Clotting Condition or Thrombophilia, May-Thurner Syndrome.”

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