testing for clotting disorders

Why Aren’t Women Tested for Factor V Leiden and Other Clotting Disorders?

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When I had a stroke at age 28, my doctors did some tests and found that I have a fairly common clotting disorder called Factor V Leiden. They told me that this, combined with birth control pills, are what caused me to have the cerebral venous thrombosis (stroke). It didn’t occur to me then to ask what Factor V Leiden actually was. Or to ask why I hadn’t been testing for inherited clotting disorders before I was put on medication that increased my risk for blood clots. These things didn’t occur to me until much later, after I learned to walk again.

I spent most of the first two years after my stroke getting on with my life. It wasn’t until I was searching for a topic for my thesis that I revisited what happened to me. I had no idea that birth control pills could be so dangerous and I certainly didn’t know that I could have an inherited genetic condition which would make them exponentially more dangerous for me. “How many women have the same condition?” I wondered. “Why don’t we test them before they are put on hormones?” These are some of the questions I sought to answer with my research.

What is Factor V Leiden?

Factor V Leiden (FVL) is a 20,000-year-old mutation common in the general population and a major genetic risk factor for thrombosis. It’s the most common genetic clotting disorder, accounting for around half of all cases. It’s most commonly found in Caucasians (3-8%).

Patients with Factor V Leiden can be either:

  • Heterozygous: inherited one mutated gene from a parent


  • Homozygous: inherited two mutated genes, one from each parent

What Does It Do?

As my hematologist described, FVL doesn’t cause blood clots but once activated, it dangerously accelerates clotting. Researchers aren’t clear on why some people with FVL activate and others don’t but there is almost always a precipitating factor—surgery, trauma, immobility, use of hormones, etc.

According to a review in Blood, the journal for the American Society of Hematology, women with heterozygous FVL who also use oral contraceptives have an estimated 30 to 50-fold increased risk of blood clots, while women with homozygous FVL have a several hundred-fold increased risk.

It is the most common genetic cause of primary and recurrent venous thromboembolism in women.

We know that taking estrogen can increase the risk of blood clots, stroke, and heart attack in women. And estrogen, when taken by someone with FVL, can significantly increase the risk of blood clots. Whether women are taking synthetic estrogen in the form of oral contraceptives, or hormone replacement therapy or have increased concentrations of the endogenous estrogens due to pregnancy, they are at much greater risk of clotting.

FVL accounts for 20-50% of the venous thromboembolisms (VTE) that are pregnancy related. In the United States, VTE is the leading cause of maternal death. In addition to causing VTE in pregnant women, FVL has been linked to miscarriage and preeclampsia.

Perhaps the women most at risk for blood clots are those that have been placed on hormone replacement therapy (HRT). A recent review of data from several studies found that women taking hormone replacement therapy were at an increased risk of blood clot and stroke. Worse yet, women with FVL who are also on HRT were 14-16 times more likely to have a VTE.

Despite these risks, women are not systematically tested for FVL before they are prescribed oral contraceptives, before or during pregnancy, or before commencing HRT.

What Women Know about Birth Control and Blood Clots

Part of my thesis research included a survey to assess what women understand about the risks of birth control pills and clotting disorders. Over 300 women who had taken birth control pills participated. What I found was that most women do not understand the side effects of hormonal birth control, nor are they familiar with the symptoms of a blood clot.

As for clotting disorders, nearly 60% of the women surveyed had no knowledge of these conditions. When asked whether they knew about clotting disorders BEFORE they took birth control pills that number increases considerably.

Over 80% of women were taking a medication without the knowledge that they could have an undiagnosed genetic condition that would make that medication exponentially more dangerous.

This shouldn’t come as much of a surprise give that this information is not found in advertisements for birth control pills, on non- profit websites about birth control pills and their risks, or on literature provided with the prescriptions.

Why Aren’t Women Tested for Clotting Disorders?

The most common reason I found in my research for not testing women were cost-benefit analyses measured in cost per prevention of one death.

Setting aside the moral argument that you cannot put a price on a human life, because clearly the government and corporations do just that. (It’s $8 million in case you were wondering.) The cost of taking care of taking care of victims of blood clots is not insignificant.

Each year thousands of women using hormonal contraceptives will develop blood clots. The average cost of a patient with pulmonary embolism (PE) is nearly $9,000 (for a three-day stay not including follow-up medication and subsequent testing).

A hospital stay as a stroke patient is over twice that at nearly $22,000 (not including continuing out-patient rehabilitation, medications, testing, etc.). As a stroke survivor, I can tell you that the bills don’t stop after you leave the hospital. I was incredibly lucky that I only needed a month of out-patient therapy. Most patients need considerably more and will require life-long medication and testing. It’s important to note that due to the increasing cost of healthcare, the figures in these studies (PEs from 2003-2010; strokes from 2006-2008) would be exponentially higher now.

I’m not a statistician but I can do some basic math and while I wasn’t able to find data for the United States (surprise, surprise), the health ministry in France recently conducted a study that showed that the birth control pill causes 2,500 blood clots a year and 20 deaths.  The United States has 9.72 million women using the pill compared to France’s 4.27 million. This doesn’t include the patch, ring, injectable, or hormonal IUD, but for the sake of keeping things simple, let’s just use the pill. So we have over twice the pill-users as France, which means twice the blood clots (5,000) and twice the deaths (40). If we assume that half of the blood clots are PE and half are stroke, we come up with a whopping $77.5 million in hospital bills for these blood clots (not counting life-long treatment). Now adding the cost-of-life determined by the government (40 women times $8 million= $320 million) and we end up with nearly $400 million a year in damages caused by the pill. For the cost of only one year of damages, all 10 million women could have a one-time $40 blood test which would result in considerably fewer blood clots.

Furthermore, the research in my thesis shows that women would be willing to not only take these tests, but also to pay for them!

Of the 311 who answered the question, 82.3% (or 256) said they would be willing to take the test. Only 7.2% said no, with the other 10.6% “not sure.” More than 60% of respondents would be willing to pay for the test (up to $50).

In addition, the cost of a blood test is directly proportional to how frequently it is performed. An increase in testing will result in a decrease in the cost of testing.

Women Deserve Better

Putting aside the monetary costs for a moment, what about the emotional and physical toll for women who suffer these dangerous and debilitating blood clots? There is no excuse for women to suffer strokes, pulmonary embolisms, DVTs, multiple miscarriages, and still births because they have an undiagnosed clotting disorder.

That said, requiring a test before prescribing hormones to women would raise awareness of the dangers of these drugs and may reduce the overall number of women using them. Which leads one to wonder if the absence of testing for women is really just a public relations strategy.

Perhaps one of the most devastating cautionary tales of not testing for clotting disorders comes from Laura Femia Buccellato. Her daughter Theresa was 16 years old when she was killed from a blood clot caused by (undiagnosed) Factor V Leiden and birth control pills. Would Theresa be with us today if she had had a simple blood test? Would I have had a stroke? When we will demand better?

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Image by fernando zhiminaicela from Pixabay.

This article was first published in September 2016.

Kerry Gretchen is a researcher, writer, stroke survivor, and a women's health advocate. She has a master's degree in communication from Clemson University, with a research focus on blood clots and hormonal birth control. When not conducting research or writing about women's health issues, she can be found teaching at the College of Charleston.


  1. I just read your article about yoga which brought me to your other excellent articles.

    I’m curious if testing standards have improved since this was written, especially in light of so many being forced to get the C19 shots which are well documented to cause blood clots. I’ve seen no warnings of who should NOT get the shots and it seems like they are pushing them on very vulnerable populations.

    Several young, healthy athletes just in Las Vegas (where I live) have died of cardiac arrests and clots after the shots. I wonder how many had FVL and were on birth control. Emma Burkey’s experience highlights how little is known about the shots. When she had a blood clot, her doc gave her warfarin which caused a massive brain bleed. He contacted the FDA for guidance, was put on hold, then they hung up on him. In his words, he was “flying blind”. She did live, but was in a coma for weeks and is severely disabled.

    How many other cases and deaths could have been avoided through proper testing and also noting drugs that cause clotting issues (SSRI antidepressants, in particular, because they are so widely used).

    Thank you for sharing this information. I wish you well.

  2. Laura here in the UK I asked the doctor to test my daughter before going on the pill for periods at 15 years old as I had my first DVT when on the pill. They happily did it and it was a great peace of mind. We are lucky with the NHS as I find my local services very good. I had a second DVT a couple of days after being immobile with illness. I have since been kept on Wafarin. I am now approaching a time when I might need HRT and thought the patches would be OK but my doctor is going to investigate this.

  3. Not sure if this thread is still active. I just came across this article as I was researching HRT for menopause symptoms. My doctor recently put me on progesterone without the typical estrogen. I cannot take estrogen because of my factor V Leiden. I am thanking you for bringing this issue to the spot light. When I was younger I had a DVT from being on BCPs. Later, I had six miscarriages in my early 30s. It wasn’t until my early 40s that an infertility specialist tested me for Factor V which I was positive for. Fortunately, with blood thinning medication I and IVF I was able to have my son later in life. But, the toll all of this took on me physically, and especially emotionally is indescribable. I also met women in my support group who had more serious long term health problems as a result of their blood clots in pregnancy including one woman with brain trauma and cognitive deficits. I learned of another woman who along with the twins died giving birth. This was fifteen years ago. Doctors still don’t test women or even bring this up with patients. I had to tell my new doctor last week about my factor v and experience as a reason I can’t go on full HRT even though it’s all over my chart. WTF?

  4. I have Factor V Leiden, am a 53 year old Caucasian woman going through the change. I’ve had horrible night sweats for 3 years (on and off) and am wondering if there is anything I can take (naturally) that will not give me blood clots.

    I’ve had 3 kids and 4 surgeries with a very surface blood clot. Please help as I am worried about osteoporosis since I can’t take normal hormone therapy medication.

  5. I found out I have factor v after my mother had a stroke and I was tested at a fertility doctor. I am now going through menopause at 48 due to a hysterectomy and am afraid to take any medication for the symptoms.

  6. My sister had a pulmonary embolism after her second c section . The autopsy described her lungs “as if it rained blood clots” . She had also a laparotomy for a huge
    Ovarian cyst prior to the C sections . Her two children tested positive for FVL.
    Today we just learned that my brother has Blood clots in his lungs, kidneys and legs .
    He tested negative for factor five Leiden decades ago but today the results are positive . We all are now going to be retested . I came across this website searching if others had a false negative testing for FFL .

    I asked if the population should be tested prior to any surgery . The surgeons said , No. A friend recently had a knee replacement and developed pneumonia and then stroked out . The wife spoke of his autopsy “ raining blood clots “ . His children tested positive for FFL

  7. Hi, I’missed 39 years old and had a stroke in May 2017 and just found out that I have this genetic disorder. I was also taking birth control pills and was never tested for this until after the stroke. The doctors could not understand how I had a stroke which finally led them to test me for this disorder.


    Natural family planning and fertility awareness methods (NFP & FAM) don’t reject complex biological clock and never harm newly conceived life, as opposed to chemical and physical “birth control” methods (especially hormonal pills and IUDs), which not only have many side effects but also often act in anti-implantation way – while using them, a woman can still have breakthrough ovulation, what occurs frequently. Unfortunately a woman can still conceive an embryo, who because of synthetic hormones (or intrusion – coil) can’t attach to the mother’s uterine lining.

  9. I was diagnosed after the c-section of my 2nd child in 1999. At the time, I lived in Eugene, Oregon. I moved to Vancouver, Washington a few months later and after is when doctors started saying I had sickle cell anemia because I am african-american. I always told the doctors I was half white but they refused to believe me because my skin is dark and I look like I am just african – american and do not fit what the doctors image of a african-american/caucasian mixed child looked liked. SO, for years I suffered from repeated DVT’s, PE’s, Strokes, heart attacks and arterial blood clots until I had my last stroke in 2011. I knew I had FVL and I knew the first doctor that tested me was right because I had all the symptoms of FVL and NONE of the symptoms of sickle cell mainly the fact that my blood cells aren’t sickle shaped at all and the gene testing I had done during the pregnancy with my twins in 2002 proved I carried no markers for it.

    When I had the stroke, I told the attending er doctor that I had FVL and he told me it wasn’t in my chart so he tested me. Not only did I have FVL, I had one of the rarest forms of it where I am a full blown thrombophilac. I had been on Lovonox and coumadin as well as heparin and a few other blood thinners for years but my INR’s always presented like I had not been taking the medicine at all.

    I am now on Pradaxa and have been since 2011 and I have not had a blood clot since. The doctor also had me have all my family members come to him directly and he tested everyone. My dad’s entire family has FVL and only a few people in my mom’s family has it. I even discovered I am missing the F5 gene and they don’t understand how I have FVL without it but it’s exactly like my late grandmother’s form of FVL.

    I keep telling people to get tested even if they don’t think it could be possible for them to have it. My goal is to make the medical community acknowledge our disease and that it’s a growing epidemic. I even got approved for my Social Security and FVL is now on their list of dangerous blood disorders.

    Never stop and never give up!

    • Wow, that’s amazing! I can’t believe all you have been through. That is so scary! Unfortunately, I can believe the doctors’ dismissals as I experienced a little bit of that myself. Were you ever on birth control when you had any of your clots? And do you have any side effects from Pradaxa?

    • I have FVL. I took birth control pills for the first year of marriage back in 1967-1968. On July9 1969 I gave birth to our daughter. A couple days after I got home I had terrible burning in my calf. I called my Dr. & he said to get to the hospital STAT! It went to my groin and they were able to stop it there. Then in the late 80’s I got another deep vein thrombosis still not diagnosed with FVL. Not until I went to an OBGYN for a yearly exam & I told her about my clots she had my blood tested & sure enough I have FVL. I was seeing a blood Dr. & they never put me on any thinners. My question is should a person be on a thinner with my history. P.S. My daughter & granddaughter both have FVL. It’s scary how they just hand out BC pills!

  10. Thank you for your research on this topic. My case of what they are calling “unprovoked pulmonary embolism”. Was actually quite different. I took birth control pills for many years ( ten years I also smoked!). I had four uneventful Caesarean section deliveries, and two (uncomplicated) knee replacements! It was not until I started a vegetarian lifestyle that out of the blue I had what they called the unprovoked pulmonary embolism! That’s when they discovered I had Leiden factor five (heterogenous). My theory has always been that it was not that it was unprovoked but instead provoked by all the vitamin K I was getting with my vegetarian lifestyle……Unknowingly of course, since I was 58 years old and knew nothing about having factor V!!!

    • Wow, Mary Lou. I knew there was connection between clotting and Vitamin K but I never imagined it was a problem unless you were on coumadin/warfarin. How do you manage your risk now? Are you still a vegetarian?

  11. I was 21 when I was hospitalized with 3 clots in my brain, nearly having a stroke. Misdiagnosed for two weeks as a drug seeker with migraines, it damn near killed me. Once we realized I had clots, we discovered the culprit with my BCP. I tested positive for FVL. Five years later, a different hematologist tested me for MTHFR, which I also came back positive for. Doctors in two different states have refused to test my mom, grandma, and other family members. Even those who’ve had DVTs in the past. They said it’s irrelevant. Now, most hematologists act like it’s nothing. I recently broke my foot and have to keep it immobilized for at least 6 weeks. Only one doctor, my hematologist, said that I needed therapy. The ER, two primary doctors, the orthopedic doctor…they all said that it wasn’t necessary. Didn’t understand why I’m at increased risk because of a broken bone. So much about FVL goes without recognition.

    • Rachel, I was also misdiagnosed. They told me I had a tension headache and that I needed to learn to manage my stress when I was actually having a stroke. I have thankfully found a very thorough hematologist, but like you, I got conflicting information from other all of my other doctors (including my first hematologist). I’m sorry you’ve had to go through so much. Please consider participating in phase II of our research study on birth control and blood clots. It starts in October. And thank you for sharing!

  12. After taking fluoroquinolones and ending up in the emergency room, my son developed clots all over his body, including his heart. After numerous external heart pumps and 2 LVADs (all that failed due to clotting) and me kicking and screaming to find out the cause for the clotting, they finally agreed to test him. We didn’t find out the results of those tests until we asked, when he was in the hospital for a heart transplant. Turns out he is homozygous MTHFR C677T. I even mentioned FVL and numerous other clotting disorders months before and it still took an act of God to finally get them to test him.

    • Ms. A, that’s terrible! I hope your son is doing okay. That’s crazy that it took so much to get him tested. Has anyone else in your family had trouble?

  13. Thank you for your continued interest an research of Factor Five. My heart breaks for Laura. 2010 our 15 year old daughter was prescribed birth control for acne. 43 days later she was in the hospital with DVT. Thank goodness she survived. It was touch and go for a few days until we were blessed to find a fantastic doctor that treated her aggressively. The prescribing pediatrician had never had a patient react to birth control pills.
    March 2016 our daughter had another occurance with DVT. She had handled some horse hormones used to promote pregnancy in mares. It took about a week but she knew something was wrong and drove herself to the hospital. She is now a full time Predaxa user. But she is alive!!!
    It has been amazing how much educating we have done to the medical staffs doctors included. I agree there needs to be more testing and educating.

    • Pam, that’s so scary! I’m glad she’s okay. And I hope she will consider participating in Phase II of our study on Birth Control and Blood Clots. Thanks for your comment!

    • Pam I am soooooo happy your daughter is ok. I would not want any parent to know the feeling of losing a child. With Theresa it all happened within 45 minutes. She was out with her friends and no one helped her and by the time they finally called her dad and he got an ambulance it was too late. I know she died as soon as they put her on the stretcher and they started cpr.
      Kerry thank you again………. I have posted this story in the factor V Leiden fb group I am in and so many people love this article and have been fighting about this for awhile. I am now heading over to Dr Oz FB page and posting this link. I have been writing him and calling for 6yrs now and am getting ignored. The only time he has ever mentioned this was in 2010 and all he said was it can cause a miscarriage. I really think if he did a show on this it would open peoples eyes, but I need people to flood his fb with this to get attention. I still am not giving up.

  14. Thank you for drawing attention to this.
    When I was first pregnant, I told my doctor FVL was common in my family and that I assumed I had it too. She tested me for it (it was positive), but my insurance denied the claim due to it being ‘not medically necesary.’ This test should be one of the many preventative services that were included in the ACA’s mandatory coverage.

    It is so frustrating that hormonal contraception is now considered safe enough to be over the counter and taken without a doctor’s guidance.

    • Elizabeth, I agree! And thank you for reading. Have you or your family had any blood clots due to FVL? My sister never did, but she was on blood thinners for her third pregnancy because it was after my stroke and we knew to test her.

  15. Laura, so sorry for your devastating loss. Kerry, thank you for bringing attention to this unaddressed issue. Young people most certainly do suffer tragically from blood clotting disorders. My brother was only 39 when he had a massive stroke and hemorraghing which all clotted in his brain. Afterwards, found out he had FVL…as do I and our mom. Of course, Mike’s stroke wasn’t related to hormones but when I tried to explain to my gynecologist that I can’t take HRT to help combat my migraines, she told me it wasn’t a big deal and hormones wouldn’t cause me any problem. Really?! Doctors need better education on this subject.

    • Christine, I’m so sorry about your brother. That’s terrible. As for doctors, I have mostly found the same. After my stroke they wanted to put me on progestin only pills but those also increase your risk for clots. I’m scared that they get most of their information about synthetic hormones from the drug companies and all the risks are downplayed. Like you did with your doctor, I’m trying to take more of my healthcare into my own hands and question the information I’m given. I think we all need to!

    • Taking hormones for postmenopause was a contributing factor for a very serious DVT that I had many years ago, also Leiden V and smoking. I quit smoking and the hormones, along with taking Coumadin for a year, and my risk factor is much lower. I always report my Leiden V presurgically now, and take a shot of thinner before international flights.

  16. I was not prepared for the last paragraph of this great article, so of course the tears are rolling down my face now. Thank you for posting this………..of course I am sharing as I always do. Just a mention by the doctor of this simple blood test and my daughter would be here today. They put a price tag on her life and did not even offer me to pay out of pocket. Now I am finding out from Factor V Leiden groups that I have joined that doctors are refusing to test children of people that have been diagnosed with this disorder. They are saying young woman and men do not suffer from clots. Really have they seen the numbers of deaths that are growing each year from this?

    • Laura, I’m so very sorry. All of the stories are tragic but Theresa’s really stuck with me. That’s terrible that they won’t test. And I will update the post to show her correct age.

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