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Factor V Leiden


The Women of Factor V Leiden

What is Factor V Leiden?

Factor V Leiden is also known as FVL. It is a genetic condition that increases the chances of having blood clots. FVL can contribute to Deep Vein Thrombosis (clots in your veins), Pulmonary Embolisms (clots in your lungs), and problems with pregnancy.

A person with FVL has inherited at least one Factor V Leiden gene from a parent. People with FVL can have one or two copies of the gene. One copy of the gene tends to cause less clotting than two copies. You will see one copy referred to as heterozygous and the two gene copy form referred to as homozygous. Heterozygous people will have a 50% chance of passing the FVL gene on to any children. Homozygous people will always pass a gene onto any offspring.

The best test to see if you have FVL is a genetic test. This test can determine if you are heterozygous or homozygous and is accurate when one has clots or is on anti coagulation medication. For these reasons, the genetic test is the most accurate.

Right now there is no cure for Factor V Leiden. Luckily, most people with FVL (90%) NEVER have a clot1. For those people who do clot, there are very good treatment options to prevent further clots.

Works Cited

  • 1.) Family Testing for Clotting Disorders
    Information about the genetics and risks associated with thrombophilias from The Ohio State University, Case Western Reserve University, and The University of Cincinnati.

The genetics of Factor V Leiden

Factor V Leiden is a genetic condition. In order to have FVL a person must have at least one parent with the FVL gene. Each person carries a pair of genes for the clotting factor known as Factor V Leiden. One gene comes from the mother and the other gene comes from the father. Factor V Leiden is a dominant gene. This means that if a person has a copy of the gene they WILL have FVL. The Factor V Leiden gene always causes a person to have FVL. The FVL gene doesn't always cause blood clots. A person with at least one FVL gene will have a higher tendency to clot but only 10% of people with FVL will clot. This is why there is a false belief that FVL can "skip" a generation. If you have one FVL gene, you have FVL. If you have FVL your child may also have FVL.

Punnet squares are a way to determine the probability that a person's offspring will have a genetic condition. Take a look at the Punnet Squares below to understand how FVL is inherited. A "n" represents a "normal" gene. A "F" represents a FVL gene. The F is capitalized because it is always dominant. If a person has at least one F they have FVL.

Both parents are normal

Both parents in this group have normal FVL genes. None of the offspring will have FVL.  100% are normal.

Both parents have homozygous FVL

When a person has two copies of the FVL gene this is referred to as homozygous FVL.  This individual has a much higher chance of clotting.  If both parents are homozygous all of the offspring will also be homozygous.  100% will have homozygous FVL.

One parent has heterozygous FVL, one parent is normal

When a person has one copy of the FVL gene this is referred to as heterozygous.  This is the most common way to inherit FVL.  This group has a 10% chance of a clotting episode.

When one parent has heterozygous FVL and one parents is normal there is a 50% chance that the offspring will be normal and a 50% chance that the offspring will have heterozygous FVL.

One parent has heterozygous FVL, one parent has homozygous FVL

When one parent has heterozygous FVL and the other parent has homozygous FVL all of the offspring will have FVL.  50% will have the more serious homozygous FVL.  50% will have the more common, less serious heterozygous FVL.

Both parents have heterozygous FVL

When both parents have heterozygous FVL 25% of the offspring will be normal and not have FVL.  Another 25% of the offspring will have the more serious homozygous FVL.  50% of the offspring will have heterozygous FVL.

One parent has homozygous FVL, one parent is normal

When one parent has homozygous FVL and one parent is normal it is guaranteed that all of the offspring will have FVL.  In this case, 100% of the offspring will have heterozygous FVL.

Links about genetics and the genetics of FVL

Suggested Links

Testing and Diagnosis

How does someone find out that he or she has the Factor V Leiden gene? This depends on the reasons for testing.

As FVL is a genetic condition, some doctors recommend having family members tested for FVL. These tests are done before the other family members have symptoms. This testing is very controversial. Testing asymptomatic individuals may cause excess worry, costs money, and may impact the availability of life insurance, The recently passed Genetic Information Nondiscrimination Act (GINA) prevents job or health insurance discrimination. On the other hand, FVL testing will allow individuals to take preemptive measures to prevent clots. Women with FVL could make birth control choices that would be safe with FVL. Also, hormone replacement (in particular estrogen) could be ruled out in order to prevent clots. People who tested positive could also use compression stockings, maintain hydration, and be cautious during travel to prevent clots. These measures could help the 10% of people with FVL who otherwise would clot. As clots can be fatal, this decision may save lives.

If a family decides not to have other members tested, it is still a good idea to share the diagnosis with everyone. Knowing the diagnosis and the possibility of others sharing the gene would allow everyone to take precautions during travel, surgery, or other high risk activities. Also, family members could learn about pulmonary embolisms and deep vein thrombosis. Learning symptoms and warning signs will help family members whether they decide to be tested or not.

Other groups that may be interested in FVL testing are women who have had multiple miscarriages, individuals with cancer, and individuals who have major lifestyles risks such as people who regularly make long haul, international flights.

There are some people who will have testing recommended by a physician. This may be recommended when:

There are a number of conditions that can cause clotting. it is important that the doctor does the tests for the full range of thrombophilias. The initial screening for Factor V Leiden will look for activated protein C (APC) resistance. The problem with this test is that anti coagulation therapy will alter the test results. While a patient has clots and/or is receiving anti coagulation therapy this test is not accurate. The other method of testing for Factor V Leiden is a genetic test. This test will look at the DNA to determine if the Factor V Leiden gene is in the correct or the mutated form. Because this test evaluates DNA, it can be done when a patient has an active clot and while a patient is on anti coagulation therapy. Also, this test will be able to determine if an individual has one or two copies of the gene. This is important as it will help to determine the severity of clotting that an individual may experience. An individual with two mutated Factor V Leiden genes has a much higher risk of clotting. For men, the genetic test will also be able to tell the patient whether the mother and/or father were the bearer of the gene.

Based on the results of the testing, the reasons for testing, and the absence or presence of other clotting conditions doctors will decide if and how long a patient will remain on anti coagulation therapy.

Suggested Links

Treatment of Factor V Leiden

Treatment of FVL will depend on if you have had clotting episodes or not. It also will vary based on if you are having problems carrying a pregnancy to term.

For those people who haven't clotted, treatment will typically consist of staying hydrated, being active, and being proactive in times when you might be more prone to clot. Hydration will help your blood flow more easily. Make sure that you are getting plenty to drink especially when out in the heat or in times when you are stationary such as airplane travel. Unlike arteries, veins have no muscles. Blood is returned to your heart using the regular muscles in your body. Staying active will strengthen those muscles and keep blood moving, thus, preventing clots.

People with Factor V Leiden need to take precautions in times when clotting may occur. Some of these times are:

  • car or air travel
  • sitting still for more than 1 or 2 hours at a time
  • being bedridden for any reason
  • illness
  • surgery
  • pregnancy

During these times, If possible, get up every hour and move around. Also, make sure to keep hydrated. If you are at a higher risk due to surgery, illness, or pregnancy speak to your doctor about ways to be safe and clot free.

If you have clotted before it is likely that you will be placed on anti coagulation therapy. Anti coagulation therapy includes drugs such as Coumadin, warfarin, Lovenox, heparin, and low molecular weight heparins. If you have only clotted once and it was with extenuating factors you may only continue anticoagulation therapy for 3 months to a year. Length of treatment will depend on your personal circumstances, health history, if there are other clotting disorders, and your doctor's preferences.

One thing that is important to note is that Coumadin/warfarin is not safe during pregnancy. It will be important to work with your doctor to find a safe alternative that will help both you and your baby be safe and healthy throughout the pregnancy and in the months following delivery.

Please see my other hubs for more detailed information about treatment and medications.

Links With Additional Information About Factor V Leiden

Useful items for FVL

Support groups


Clinical research on Factor V Leiden


Brus on September 02, 2013:

If you interesting genetics and you need free and professional punnett square tool you can look on Bifido Punnett Square Calculator :


teamrn from Chicago on July 01, 2012:

That's one thing about your parents, but my sis has a husband, children and those children will probably have children. I've not been denied life insurance because of fvl, I've been denied b/c of lupus.

Granted, it was my sister's choice to listen to her doc, but physicians must know the trust the public places in them, and they must wield it wisely.

Lena Welch (author) from USA on July 01, 2012:

We chose for my parents not to be tested and just use precautions and let doctors know about my genetics.

You have two though which could change the vote on how useful it is . Testing seems to be fairly controversial - mainly because if you only have one thrombophilia you have a low risk of clotting and as mentioned it can cause problems with some forms of insurance.

Education and prevention are your sisters best bet. A fvl DNA test would only be a risk to life insurance not health insurance due to Gina.

teamrn from Chicago on June 30, 2012:

Speaking of the need for testing or not testing, when I was dx, I told my sibs what my doc told me: hat because of the hereditary nature, they ought to be tested and then I said no more!

I felt it was so COMPLETELY irresponsible of my sister's physician who said, "Nah, you don't need to be tested: your insurance rates might go up!1'

Lena Welch (author) from USA on June 30, 2012:

APS tends to effect inr testing. The home and point of care ones can be a problem for some people. I bet you have done your research though as you already found the apsfa. This means testing can show wacky levels even when you are fine. Didn't know the actual levels were affected too. What a pain! Sounds like you have some great resources and you did the hard part and survived! Now for the boring part - healing and coping.

teamrn from Chicago on June 30, 2012:

I'm pretty much 'grouped-out!' but I belong to a yahoo group about a little known disease caused by clots and clotting disorders, APS affects my INR so much that stability of coumadin doses is a virtual impossibility. (One more sneeze this week than last week will throw my INR off), so my coumadin doses change 2-3 times a week.Thank goodness I was able to qualify for a home INR machine. I do belong to the apsfa and my way of coping with the bizarre disorders is to blog about them. May be a form of denials, escapism, but...

Lena Welch (author) from USA on June 30, 2012:

They are separate disorders. You can jump to my thrombophilia page for some basic info. Factor v Leiden is a mutation that changes how factor v fits with other chemicals to turn off clotting. I have one copy of the mutant gene so half of my factor v is resistant to activated protein c. This means half of my factor five turns off clots and the other half doesn't do that so well.

APS is a disease in which antibodies cause the problems. Clots are common in arteries in this problem vs veins in fvl. Apparently clots like to reoccur in the same location with APS.

Anticoagulation will likely be a blessing for you. Go through my links. There are a lot of great organizations for clotting problems. Daily strength and yahoo groups have some great online support groups.

As I don't know a lot on APS, I included some links for you below.

Happy healing!




teamrn from Chicago on June 30, 2012:

I have factor V and I don't know much about though I think I inherited the tendency from my mother-or both parents. Because of the facto V, I'm no coumadin for life and. Unfortunately-or fortunately, it has been the least of my worries, though I wonder if the facto V is the cause of antiphosophlipid syndrome that I have.

Lena Welch (author) from USA on June 30, 2012:

It is easy to miss. 4% of the population has fvl but only 10% of us with fvl ever clot. If you have question drop me a note through hubpages.

Bobby from U.K on June 30, 2012:

I was diagnosed with FVL 3 months ago when I was admitted to hospital with a 3 foot clot in my leg and pulmonary embolisms. I had no idea that the clot was growing in my leg but it now explains all my symptoms over the past few years. I'm now on anti-coagulants for the rest of my life because my doctors missed this.

teamrn from Chicago on March 16, 2012:

I have factor V and because of that and several other medical conditions am on Coumadin in for the rest of my life.

Lena Welch (author) from USA on June 21, 2010:

I would recommend just asking for a genetic test. "I would like to have a genetic test for FVL to see if I have it or not and to see if it is heterozygous or homozygous." Making sure to mention genetics and DNA should get the right test. Ask the Dr if it is looking at those items. The other FVL tests do not, they just look at blood counts.

Carolyn on June 19, 2010:

Evidently there are physicians that do not know what test to use for Factor V Leiden. Within the past year, 2 of my granddaughters, from different parents, have been diagnosed with pulmonary embolism and then tested positive for Factor V Leiden. I tested negative by use of DNA test using the FDA approved Roche assay for Factor V Leiden. My daughter requested that her physician test her for Factor V Leiden but when results were received, she had been tested for "Factor V Activity". Now she will have to be tested again. What is the best terminology to use to ensure you receive the correct lab test for Factor V Leiden?

Lena Welch (author) from USA on May 29, 2010:

I just looked around to see if I could answer that question. I had a TON of blood work done and it was done while I was an inpatient in the hospital. This means I have no clue what my costs were. I searched online and while I can find a lot of companies that do the lab work, none list tests as they would be working with Doctors rather than patients. It is a fairly common test if you only get the FVL one so I bet the price isn't terrible. I think my hospital ran my DNA in house even.

Erika on May 26, 2010:

what is the cost of the factor v leiden genetic analysis?

Lena Welch (author) from USA on July 17, 2009:

I am glad that this was useful! If you have any questions, feel free to message me. I think the biggest thing is knowing good "clot prevention hygeine" and the symptoms and signs of a clot. My family has not been tested, but you bet I will watch if my parents ever have health issues that have them in bed or in surgery. I hope that you have avoided some of the nastier clotting scenarios yourself. Best wishes!

Janet Pina on July 17, 2009:

This is the most useful website I have read since being diagnosed with FVL last September. I have 3 grand-daughters and am pondering what to tell them about testing. This information is very helpful. Thank you!

moonlake from America on December 28, 2008:

My brother has this I don't.

good information.