Genetics and DVT

Medically Reviewed by Carmelita Swiner, MD on November 30, 2022
7 min read

Genetic conditions like factor V Leiden and a prothrombin gene mutation can make it more likely that you will develop health problems because of blood clots. And being prone to blood clots can put you at risk for two health conditions:

  • Deep vein thrombosis (DVT). This is when certain parts of your blood thicken and form a clot in a vein. These can happen anywhere in your body, but they most often affect one leg. They're especially likely if you've been sitting for hours at a time, like when you're on a long flight.
  • Pulmonary embolism (PE). This is when a blood clot breaks away from where it formed, travels through your bloodstream, and lands in your lungs. It can put a strain on your heart and cause problems with maintaining oxygen levels.

Factor V Leiden (FVL) is a change in your genes that affects one of the clotting factors in your blood and keeps your body's blood-clotting process from working right. It can cause a disorder called factor V Leiden thrombophilia.

When you get a cut or scrape, your body forms a clot to stop the bleeding. Clots are clumps of blood cells called platelets and protein strands in the liquid part of your blood called plasma. Factor V (factor 5) is one of several special proteins in your blood that help it clot. They're called clotting factors. Once the bleeding stops, other proteins tell your clotting factors to break up the clot, and it goes away.

Factor V Leiden makes it harder for your clots to break up. If the clots don't go away, you're more likely to have them in the veins in your legs. This is called deep vein thrombosis (DVT). You also have higher chances of getting clots that travel through your bloodstream. These can block the arteries in your lungs, which is called pulmonary embolism (PE).

Factor V Leiden is also known as Leiden type, APC resistance, and hereditary resistance to activated protein C.

You get factor V Leiden because of your genes. That means you were born with a change or “mutation” that causes it. You can get it from one or both of your parents.

About 5% of people in the United States have factor V Leiden. It's most common in people of Northern European descent.

If you've had any of these signs, get checked for factor V Leiden:

Blood clotting requires a protein called prothrombin. If you have a prothrombin gene mutation, your body makes too much of it, which puts you at risk for blood clots.

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.

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

Both factor V Leiden and a prothrombin gene mutation do not have symptoms on their own, and some people may never know that they have them.

But it is important for anyone to know the symptoms of blood clots, DVT, and pulmonary embolism.

Symptoms of a blood clot include:

  • Pain
  • Redness
  • Swelling
  • Warmth

Symptoms of DVT include:

  • 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

Symptoms of a pulmonary embolism include:

Since there's no cure for these genetic mutations, 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 probably won't need any treatment. You'll just need to know, and watch for, the symptoms. Make sure your doctors know about it if you're having surgery, if you're pregnant, or if you're planning a pregnancy.

If you need treatment, you'll take a blood-thinning drug to help prevent clots from forming. Doctors call these medicines anticoagulants. Two of the most common are:

  • Heparin. This medication works quickly. Your doctor can inject it into a vein (intravenously) or under your skin (subcutaneously). Or you may be able to give yourself the injection. This drug is safe for pregnant women. Heparin may have side effects including excess bleeding and allergic reaction. There's no standard dose, so you'll need to have blood tests that will help your doctor figure out how much is right for you. You may need to adjust the dose from time to time, too.
  • Warfarin (Coumadin, Jantoven). You take this medication as a pill. There's no standard dose for it, either, so as with heparin, you'll need to see the doctor often for tests and adjustments. It can cause bleeding, and it isn't safe for pregnant women, especially the first trimester. Tell your doctor about anything else you're taking when you start warfarin. It can affect the way other drugs and herbs work.

Or you might take anticoagulant pills that don't need testing and adjustments but might make you more likely to bleed. These include:

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 one of these genetic conditions, make sure your doctor knows that before you start such treatments.

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:

Women who have factor V Leiden are two to three times more likely to lose a baby in the second or third trimester. This can happen more than once. It can also make you more likely to get high blood pressure during pregnancy (called preeclampsia) or early separation of the placenta from your uterine wall (called placental abruption). Factor V Leiden can also make your baby grow more slowly.

How to lower your risk of blood clots

If you have a genetic condition that puts you at risk for blood clots, you can make lifestyle changes to lower the chance that you will get one.

  • Be safe. Avoid bruises and cuts. Try not to bump or injure your legs. Don't cross your legs when you sit down. Choose solo exercise rather than contact sports. At home, use a soft toothbrush and an electric razor. Be careful with knives, scissors, and other household tools.
  • Stay active. Even if you've been on bed rest after surgery or for other reasons, get moving as soon as your doctor gives you the OK. That's a sure way to help prevent blood clots. Don't sit or stand still for more than an hour at a time. Change positions often, especially if you're on a long trip.
  • Be smart about hormones. Talk to your doctor before getting pregnant or starting hormone replacement therapy.
  • Wear compression stockings. They aren't pretty, but they'll help keep you from getting a clot.
  • Eat a healthy, low-salt diet. Extra pounds put more pressure on the veins in your pelvis and legs. Salt boosts your blood pressure. Keeping sodium and cholesterol low can help you avoid 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.
  • Quit smoking. It affects blood flow and circulation, which can raise your risk of a clot.
  • Lift up. Raise the bottom of your bed 6 inches off the ground. You can use blocks, books, or special risers you can find online or at home stores.