Patient education: Factor V Leiden (The Basics)

What is factor V Leiden? — Factor V Leiden (also called "FVL") is a condition that makes blood more likely to form clots in the legs, lungs, and other parts of the body in some people. The letter "V" is the Roman numeral for "5," so "factor V" means "factor 5." Leiden is a city in Holland where the gene that causes this condition was discovered.

Factor V Leiden is a lifelong condition that a person is born with. It is caused by a single change in the gene that the body uses to make a protein called factor V. The factor V protein helps your blood clot.

Children with factor V Leiden can get the changed gene from 1 or both of their parents. But usually, it comes from just 1 parent. About 4 to 5 percent of White people have the gene. It is much less common in people of color.

Most people with the changed gene do not know they have it because they don't have any symptoms. Some people with the changed gene have a higher risk of blood clots.

What are the symptoms of factor V Leiden? — Most people with factor V Leiden never have any symptoms. But some people with factor V Leiden have a higher risk of getting blood clots, especially in the leg or the lungs. When clots do occur, they can cause:

●Warmth, redness, pain, and swelling in the leg – These are symptoms of a condition called "deep vein thrombosis" or "DVT." This is a blood clot in a vein in the leg.

●Breathing problems, sharp chest pain, coughing, fast heartbeat, and passing out – These are symptoms of a condition called "pulmonary embolism." This is a blood clot in the lungs. It usually comes from a blood clot in the leg that breaks off and travels to the lungs. This can be very dangerous and can even cause death if the clot is large.

Some doctors believe that factor V Leiden can also increase the chance of other problems, including stroke, heart attack, or miscarriage (when a pregnancy ends on its own before the baby can live outside the womb). But other doctors do not. If there is an increased risk of these conditions, it is a small increase.

Should I see a doctor or nurse? — Call your doctor or nurse right away if you think you might have a blood clot in your leg.

If you have symptoms of a stroke or a blood clot in the lungs, call for an ambulance (in the US and Canada, call 9-1-1). These conditions are very serious and can be life-threatening.

Signs of a stroke include:

●Drooping of 1 side of the face

●Arm weakness

●Trouble speaking normally

Signs of a blood blot in the lungs include:

●Breathing problems

●Sharp chest pain

●Coughing

●Fast heartbeat

●Passing out

If 1 of your relatives has been told that they have factor V Leiden, you can talk to your doctor or nurse to find out if you should be tested.

Is there a test for factor V Leiden? — Yes. If your doctor or nurse thinks you might have factor V Leiden, they can order a blood test to look for the change in the gene.

If you do have factor V Leiden, you can tell your relatives (parents, siblings, or children) so they can decide whether to be tested. Their doctor or nurse can help them make this decision.

How is factor V Leiden treated? — If factor V Leiden causes a blood clot, the main treatment is to take a medicine that keeps the clot from getting bigger. Some of these medicines come in shots and others come in pills. If the clot is severe, doctors sometimes use a stronger medicine that gets rid of clots or do surgery to remove a blood clot in the lungs.

People who have had a blood clot usually take a medicine in pill form to prevent clots for at least 3 months after the clot is found, and often for longer. This medicine helps prevent new blood clots from forming. It is important because people who have a clot often get another one later. Some people have to take the medicine for the rest of their life.

Is there anything I can do to prevent blood clots? — Yes. The best thing you can do is move your legs often. This keeps the blood moving. Not moving for a long period of time can increase your risk of clots.

Sometimes you might not be able to move around a lot. Examples include having surgery, being stuck in bed, or taking a long airplane or car trip. When this happens, there are things you can do to lower your chance of getting a clot.

To help prevent a clot on a long trip, you can:

●Stand up and walk around at least once every hour, if you are on a plane or a bus

●Stop every hour or so to get out and walk around, if you are driving or riding in a car

●Wear loose, comfortable clothes

●Change your sitting position and move your legs and feet often

●Wear knee-high compression stockings, especially if you get leg swelling

To prevent a clot during surgery, your doctor can give you a medicine or take other actions to prevent blood clots. If you are having surgery, make sure to let your doctor know you have factor V Leiden.

People with factor V Leiden should ask a doctor if it is safe for them to take birth control pills or other hormone treatments. The hormones can raise the risk of blood clots. Often, people with factor V Leiden should use a different form of birth control (like an IUD) or a different treatment for acne, if needed.

What if I want to get pregnant? — If you have factor V Leiden and want to get pregnant, talk to your doctor or nurse. They will work with you to lower your risk of blood clots.

More on this topic

Patient education: Deep vein thrombosis (blood clot in the legs) (The Basics)
Patient education: Pulmonary embolism (blood clot in the lungs) (The Basics)
Patient education: Stroke (The Basics)

Patient education: Deep vein thrombosis (DVT) (Beyond the Basics)
Patient education: Stroke symptoms and diagnosis (Beyond the Basics)
Patient education: Warfarin (Beyond the Basics)