Patient Education Blog

DVT and PE: How Long to Treat with “Blood Thinners”

Stephan Moll, MD writes…

What Kind of Clot did You Have?

If you have had a blood clot in your legs or your lung (pulmonary embolism=PE), you will wonder how long you should stay on a “blood thinner”. The decision depends on a number of factors which will be discussed below.

  • First, you and your doctor will want/need to know where in the extremity the clot was, as this influences management: Was it (a) a superficial clot (= superficial thrombophlebitis; surface clot) or was it a DVT (deep vein thrombosis; clot in the deep veins of the leg or pelvis)?
  • If you had a DVT you will want to know: was it in the veins below the knee (=distal DVT) or in the veins in your thigh or pelvis (= proximal DVT). The anatomy of leg veins is shown here.

This blog entry will discuss management of leg DVT and of PE.  Management of DVT of the arms and superficial thrombophlebitis will be discussed in separate blog entries.

Risk-Benefit Assessment

Whether short-term or long-term “blood thinners” should be given depends on:

  • (a) How high the risk of another clot is if the person comes off “blood thinners”, and (b) the risk of bleeding if the person remains on them. Thus, the decision to continue or discontinue “blood thinners” is a risk-benefit assessment: risk of a new clot off “blood thinners” versus risk of bleeding on “thinners”.
  • In addition, it is important to take into consideration the patient’s preference, i.e. whether he/she minds being on a “blood thinner” (fluctuating or stable INRs?; frequency of clinic visits for INR monitoring; expense of the drug and clinic visits; impact of being on blood thinners on profession and hobbies; side effects).

If the risk of another clot is low, then short-term treatment for only 3 months is sufficient. This is long enough for the present clot to heal. However, if the risk for another DVT or PE is high, then treatment for more than 3 months is appropriate. This typically means long-term treatment, i.e. for several years.  However, reevaluation in clinic once per year is appropriate to see whether continuation of the “blood thinner” is still the right thing to do.

Length of Treatment

A.  Provoked leg DVT or PE

a)      Provoked by a major temporary risk factor
3 months of “blood thinners” are typically all that is needed if a DVT (no matter whether distal or proximal) or PE was associated with a major transient risk factor, such as

  • major surgery
  • hospitalization
  • prolonged immobility (more than 3 days of bedridden state; cast or immobilizer after a bone fracture)
  • major trauma
  • long-distance airline travel (fights more than 12 hours).

Once off  “blood thinners”, the risk for future DVT or PE is low. Less than 5 % (i.e. less than 1 out of 20) of these patients will develop another clot over the next several years [ref 1].  In this situation, no wok-up for a clotting disorder (thrombophilia) needs to be done, because the treatment would still only be 3 months, even if a thrombophilia was detected.

b)      Provoked by a minor temporary/transient risk factor
Treatment decisions are more difficult if the DVT or PE was associated with a minor risk factor only, such as

  • minor trauma
  • minor surgery (e.g. arthroscopic surgery, plastic surgery)
  • birth control pill, patch or ring or other estrogen therapy
  • pregnancy
  • less than 12 hour airline travel.

In these patients treatment with “blood thinners” for 3-6 months may be all that is needed. However, the risk of another clot in this group of patients may be higher than in the group mentioned above who had a strong triggering factor. It is this “gray zone” group of patients with some intermediate risk of recurrence where length of treatment decisions are difficult. Presence of additional risk factors for recurrence (overweight, presence of postthrombotic syndrome, positive D-dimer test results, age > 65, strong thrombophilia) might argue for longer-term “blood thinners”, absence of such risk factors for discontinuation.

B.  Unprovoked DVT or PE

If a DVT of PE occurs out of the blue, without any clear triggering factor, it is referred to as unprovoked or “idiopathic” DVT or PE. The length of “blood thinner” treatment in the case of leg DVT depends on where in the leg the DVT was – distal (below the knee) or proximal (behind the knee or in the thigh or groin).

a) Distal DVT (i.e. below the knee, in the calf). Length of treatment is typically 3 months only [ref 2].

b) Proximal DVT (pelvis, thigh, and/or behind knee) or PE
At least 3-6 months of “blood thinners” are typically recommended, with a preference for long-term (also referred to as “extended”) treatment, if the patient tolerates therapy well [ref 2,3]. There have been attempts to identify which of these patients have a higher and which have a lower risk of recurrence, i.e. in whom one can safely discontinue “blood thinners” and who clearly needs long-term therapy. Unfortunately, for some of these determinants, data from clinical studies are not very solid or too premature. Sometimes, different studies have provided discrepant results. This is a field of knowledge that is changing rapidly. Possible determinants of a higher risk for future clots are:

  1. Gender (men have a higher risk for recurrence than women)
  2. Presence of a strong clotting disorder – see table (Strong thrombophilias)
  3. Obesity
  4. Significant chronic leg swelling (postthrombotic syndrome)
  5. Positive D-dimer blood test obtained while the patient is still on the “blood thinner”
  6. Positive D-dimer blood test obtained 4 weeks after having come off the “blood thinner”
  7. A lot of left-over (residual) clot on follow-up Doppler ultrasound examination of the leg.
  8. Strong family history of unprovoked DVT or PE.
  9. In addition, patients who had a PE more likely have a PE as a recurrence and have a higher risk of dying from the recurrent clot, compared to patients who “only” had a DVT.

The image (How long to treat) shows how I approach the length of “blood thinner” therapy decision in 2011. In men with an unprovoked DVT or PE, I have a tendency to recommend long-term “blood thinners”, particularly if the clot was a PE. In women who had a DVT or PE,  it would be reasonable to consider discontinuation of “blood thinners”, if the woman is of normal weight, does not have postthrombotic syndrome, is less than 65 years old , and has a negative D-dimer.

C. Recurrent DVT or PE

If a patient has had 2 or more clots long-term “blood thinners” are not automatically needed. The decision how long to treat still depends on what triggered each of the episodes of DVT or PE.

  • The patient who had 2 episodes of DVT or PE, each associated with a major transient risk factors, such as surgery, will not need to be on long-term “blood thinners; he/she “just” needs very good DVT prophylaxis in the future after major surgeries.
  • However, the person who has had 2 episodes of unprovoked (idiopathic) DVT or PE, clearly shows that he/she “likes” to clot. In that person, long-term “blood thinners are clearly needed.

What does “Long-Term” Therapy Mean?

It means treatment for many years to come, but reevaluation once per year, to see whether continuation of “blood thinner” therapy is still the right thing to do in this patient. Things to consider and discuss with your thrombosis doctor at such an annual follow-up visit are:

  • How have you tolerated the “blood thinner” in the last year? Have you had bleeding problems or any new clots?
  • If you are on warfarin, have your INRs (blood test to measure how “thin” your blood is) been up and down and unsteady/fluctuating, or very steady? How often do you need to get your INR tested?
  • What new studies have come out that might tell us who is at low risk for a future blood clot and who is at higher risk if off “blood thinners”?
  • Is it unacceptably expensive for you to be on a “blood thinner” or getting it monitored?
  • Do you mind being on a “blood thinner” and what is your own preference regarding
  • being on it or not?
  • Have new “blood thinners” been FDA approved and are they now available? Might they be suitable for you to switch to?
  • Are there any DVT or PE studies that you could enroll into? To stay up-to-date you can sign-up for the monthly Clot Connect Newsletter, check the “research to participate in” section (in development) of the Clot Connect website or check the NIH clinical trials website.

Does having a thrombophilia (clotting disorder) mean that I should be on long-term “blood thinners”?

Decisions on how long to treat a patient with “blood thinners” are often independent on whether a thrombophilia is present or not. The decision is typically primarily based on the circumstances of the first clot (DVT or PE), i. e. whether it was triggered by a temporary risk factor or whether it was unprovoked (= idiopathic).  If the clot was triggered by a major temporary risk factor, such as major surgery, then 3 months of therapy are sufficient. This is also true, if a mild clotting disorder, such as heterozygous factor V Leiden or heterozygous prothrombin (=factor II) 20210 mutation, is found. In patients with unprovoked (idiopathic) DVT or PE on the other hand, long-term “blood thinners” are often recommended, and this recommendation is the same, no matter whether a thrombophilia is present or not.

One of the few times that finding a thrombophilia really makes a difference in the “blood thinner” treatment of a patient is in the following two scenarios: (a) If a patient had a DVT or PE associated with a mild risk factor (such as birth control pill), the finding of a strong thrombophilia (see table) may lead to long-term therapy with “blood thinners”; whereas finding of no thrombophilia or only a mild thrombophilia (such as heterozygous – i.e. one variant gene –  factor V Leiden or heterozygous II20210 mutation) may lead to discontinuation of “blood thinners” after 3-6 months; (b) in the patient with unprovoked DVT or PE who does not tolerate warfarin, very much dislikes being on it, or is thought to have a lowish risk of recurrence (women with DVT only) – see the image (How long to treat):  in these patients the finding of a STRONG thrombophilia would be a reason to continue “blood thinners”, while the finding of no or only a mild thrombophilia might lead to discontinuing them.

The Risk-of-Recurrence and Risk-of-Bleeding Calculator

It would be nice to have a web-based calculator into which one could enter a patient’s clinical details about the first clot, the patient’s risk factors for recurrent clot as well as for bleeding, so that the calculator would spit out a risk-benefit assessment whether this patient should remain on “blood thinners’ or come off. At present there are not enough data from good, solid, prospective clinical trials to make such a calculator reliable, but increasingly such data are being published [ref 6,7]. At some point in the future such a calculator will likely become reality.

Existing Guidelines for the Treatment of DVT and/or PE

Well respected treatment guidelines have been published for health care professionals 1,2, developed by a panel of national and international experts who reviewed all published clinical trial data and came up with evidence based treatment recommendations.

  • The comprehensive ACCP (American College of Chest Physicians) guidelines are highly valued[ref 2]. They are brought up-to-date every 3-4 years.
  • A very solid, yet less comprehensive guideline (does not cover DVT of the mid-thigh, or distal leg; does not cover superficial thrombophlebitis) was published in 2011 by the American Heart Association[ref 3].
  • For many health care providers, these guidelines are a little cumbersome to use in clinical practice, due to their extensiveness and complexity. Solid down-to-the-point, practical “How-to” summaries have, therefore, been published [ref 4,5].

Key Points for the Patient

  • Know whether you had a superficial clot (superficial thrombophlebitis) or a deep vein clot (DVT).
  • If you had a DVT, know whether it was below the knee (=distal) or behind and/or above the knee (=proximal DVT).
  • If you are not sure what kind of clot you have/had and where in the leg it was, print out this leg vein anatomy drawing and ask your health care professional to mark where your clot is/was.
  • Know the risk factors that triggered your clot.
  • Ask your health care professional how long he/she thinks you should be on “blood thinners”.
  • Ask whether obtaining a D-dimer would be helpful, a thrombophilia work-up, a repeat Doppler ultrasound of the leg to look for residual clot.
  • Find out whether there are any clinical studies you could participate in.
  • If you are on long-term “blood thinners”, rethink once per year with your physician whether you should still be on it. Inquire about new studies published, new “blood thinner” drugs available.

Patient Questions /Examples – Explanations

Question #1: “I have been told that I need to be on blood thinner for life. I have factor V leiden….Is this the truth????????”

Answer #1: The questions you should ask your doctor are clear: (a) did I have a proximal DVT or PE, or only a distal DVT? (b) what were the triggering factors for my clot (immobility, surgery trauma, long-distance travel, etc)?, (c) what clotting work-up was done beside of factor V Leiden?, (d) do I have one or two abnormal genes for factor V Leiden, i.e. am I heterozygous or homozygous?. Once you have this information, you often have an inkling on whether it is appropriate to be on long-term “blood thinners” or not, based on published guidelines and, hopefully, the preceeding discussion in this Clot Connect blog entry. You should also ask your physician: (e) What is my risk of recurrent clot if I am off “blood thinners”?, (f)) how long should I be on “blood thinners”?, and you might ask: (g) is it worthwhile for me to be referred to a Thrombosis Center for specialist input?.


  1. Iorio A et al. Risk of recurrence after a first episode of symptomatic venous thromboembolism provoked by a transient risk factor: a systematic review. Arch Intern Med. 2010 Oct 25;170(19):1710-6. Review.
  2. Kearon C et al. Antihrombotic therapy for VTE disease. Antithrombotic therapy and prevention of thrombosis, 9th ed: American College of Chest Physicians evidence-based clinical practice guidelines. Chest 2012;141(2)(Suppl):e419S-494S.
  3. Jaff MR et . Management of massive and submassive pulmonary embolism, iliofemoral deep vein thrombosis, and chronic thromboembolic pulmonary hypertension. AHA A scientific statement from the American Heart Association. Circulation 2011;123(16):1788-830.
  4. Bauer K. Duration of anticoagulation: applying guidelines and beyond. Am Soc Hematol Education Program Book 2010;210-215.
  5. Goldhaber SZ et al. Optimal duration of anticoagulation after venous thromboembolism. Circulation 2011;123:664-667.
  6. Rodger MA et al. Identifying unprovoked thromboembolism patients at low risk for recurrence who can discontinue anticoagulant therapy. CMAJ 2008;179:417-426.
  7. Eichinger S et al. Risk assessment of recurrence in patients with unprovoked deep vein thrombosis or pulmonary embolism: the Vienna prediction model. Circulation. 2010 Apr 13;121(14):1630-6

Disclosure:  I have no relevant financial conflict of interest with this blog entry.

Last updated: Feb 1st, 2013

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32 Responses to “DVT and PE: How Long to Treat with “Blood Thinners””

  1. JANELL says:

    I was diagnosed with a PE; I was 8 weeks pregnant. Is it likely that it can just be a one time thing or should I expect more down the line? My iron was real low before I got pregnant – does low iron play a part in clotting?

  2. Binyam Kassa says:

    I had an unprovoked PE twice in a three months period and none of my ultrasounds show a clot in my legs. My doctor is suggesting a life-time blood thinner. I am 28 yrs old and I have been on blood thinner for a little more than a year now and would like to get off. What would be the smart way to get off the drug without risking another clot. A series of tests were performed and they couldn’t pinpoint any trigger for my clots. Any suggestion would help.

    • Stephan Moll says:

      To fully understand what is going on here, one would want to know: (a) Did the patient truly have a second clot? (b) What were the circumstances of the 2nd clot – was the patient not on “blood thinners” any more?; or was the level (INR) of the “blood thinner” too low?; (c) Age of the patient; weight (body mass index); what kind of work-up for a clotting disorder was done; has malignancy (cancer) been ruled out; is there a family history of blood clots?

      In patients with one episode of unprovoked PE, the preference is to treat with long-term with “blood thinners”, if they are being tolerated well. If the patient truly has recurrent blood clots, then the patient has already shown that he/she “likes” to re-clot, and the recommendation to stay on long-term “blood thinners” is even stronger. However, before one commits a patient to long-term “blood thinners”, one would really want to be sure that what is being called a “recurrence” was, indeed, a recurrence, i.e. a second blood clot. If it was not a recurrence, then the discussion of the above blog “How long to treat with blood thinners” applies and one could discuss using the D-dimer, HERDOO-2 score, etc. for decision making.

  3. natalie says:

    if a DVT goes from the entire leg into the inferior vena cava, does that mean it started in the IVC and extended down into the leg, or vice-versa? And if thrombosis extends into the IVC, do the typical treatments as discussed above apply, or should it be treated differently?

    • Stephan Moll says:

      It is not clear where such extensive DVTs start – in the leg and then extend upwards, or in the IVC and then extend downwards. If the DVT is in the left leg, I wonder whether it started in the deep veins in the left pelvic due to pre-existing May Thurner syndrome. Yes, the thought process about length of blood thinner treatment decisions is similar.

  4. Wes Price says:

    I had a provoked DVT in may from ACL surgery. I have also been diagnosed w/ factor V leiden heterozygote. I am a 30 year old very active male. From what I read 3-6 months of blood thinners is the recommendation, just wondering if I read that properly? My doc says 6-12 months depending but I am ready to be off them ASAP. Any ideas?

    • Stephan Moll says:

      I suggest you discuss this with your MD. Ask why he/she recommends 6-12 months, rather than the 3 months only often given for a DVT secondary to a transient (reversible) risk factor.

      • Wes Price says:

        Thanks for your help and replying so promptly. I have a meeting with my Doc this week to discuss the issues I have. Is there anything on the probability or % chance that I would have another DVT if I come off the thinners? This is the only thing that concerns me. I have read that my chances to randomly form a DVT are very slim & should only be concerned if I have a trauma or another surgery. Any thoughts on this? Anything I can take/do/eat to be as proactive as possible against this. I just want to live my life without the worry. Thanks again for your help.


      • Stephan Moll says:

        1. Risk of recurrence: The risk of recurrent DVT or PE in the patient who had a clot associated with surgery and who stops blood thinners after 3 or more months of treatment is low, 1.4 % over 2 years. I.e., 1 of 70 patients develops a new clot (Iorio et al. Risk of recurrence after a first episode of symptomatic venous thromboembolism provoked by a transient risk factor. Arch Intern Med 2010;170:1710-1716]. This systematic review included patients with any type of surgery associated DVT or PE, i.e. either major or minor surgery, and the 1.4 % risk of recurrence is an average of these patients. It is possible that patients with certain surgeries have a lower or higher risk of recurrence than this average, such as that the recurrence rate is higher for those whose clot was associated with minor surgery.

        2. How to minimize future risk of DVT or PE? Good DVT prophylaxis in risk situations; normalize weight; stop smoking; not delaying diagnosis if symptoms of DVT or PE occur. Long term aspirin probably is not effective; whether natural products such as (Nattokinase) are helpful in decreasing risk is not known.

  5. Em says:

    I was on hormonal birth control pills for over ten years before developing a blood clot (pulmonary embolism) at the age of 28. After a harrowing experience that ended up with a week in the hospital on Heperin, I was kept on Coumadin with regular testing, etc. It’s been 5 months and my doctor has said that I’ll be on the thinners for at least a year. I can’t figure out how she has made this determination; I’m thinking about getting a second opinion. (For that and other reasons; I’m not thrilled with the competency of her office staff either.)

    I’m wondering how many other people go through this… I’m generally not scared of much, but frankly the idea of stopping the drugs, as much as I want to be finished with them, terrifies me. Does anyone know what the process is for finishing the treatment? How do I know that I won’t develop another clot from some residual chemicals from the birth control pills? I know I was lucky to feel pain before the last one; it freaks me out that I could have just dropped dead from a stroke.

    Are there any general resources for information about this? A list of good doctors? It’s so frustrating to think that I have no control over what’s going to happen to me; I’m not even 30. (On a side note, anyone else think that they should monitor young women on the potential side effects of hormonal birth control? I was never told anything about what might happen when they first prescribed the Pill for me at the age of 15.)

    • Stephan Moll says:

      1. “Does anyone know what the process is for finishing the treatment?
      At the end of the 3-6 months treatment with blood thinners an assessment is made what a patient’s (a) risk of recurrent clot is if he/she came off blood thinners, and (b) risk for bleeding is if he/she stayed on blood thinners. A patient’s own preference regarding staying on or coming off blood thinners is also taken into consideration. A decision is then made to stop or continue the blood thinner. If one decides to stop blood thinners, then the patient just stops taking warfarin. It will be out of the system within approximately one week. There is no need to taper warfarin. Pradaxa is out of the system in approximately 2-3 days. I always obtain a Doppler ultrasound of the legs or arms (in case of a history of leg or arm DVT), as a baseline study. The results of this study are NOT used to help in the decision process whether to stop or continue blood thinners. But it serves as a baseline study in case future problems arise, such as recurrent extremity swelling or pain. It may then be easier to determine whether a new clot is present or whether the changes seen on a Doppler ultrasound are just old/chronic changes, i.e. scar tissue. If a patient was on blood thinners for a PE, I do not routinely obtain a CT of the chest of VQ nuclear medicine study as a baseline when the patient stops the blood thinner, because of the radiation involved with the Xray study. If the patient and I decide that he/she will continue warfarin, reevaluation once every 6-12 months is appropriate, to revisit, whether the patient should still be on a blood thinner.

      2. “How do I know that I won’t develop another clot from some residual chemicals from the birth control pills?”

      The effect of the birth control pill is out of a system within a few days or weeks. Independent of that issue, if new symptoms occur – new leg swelling, pain, warmth or redness in the extremity, or shortness of breath, chest pain, unexplained cough or fast heart rate – recurrence of a DVT or PE should be considered and the patient should seek medical attention.

      3. “Are there any general resources for information about this?”
      I hope that the comments above provide some answers. Clot Connect is also in the process of writing a brochure “Newly diagnosed with DVT or PE – What to expect”, which will take reference to the issues you raise above: the time when a patient is coming off blood thinners and the months afterwards.

      4. “A list of good doctors?”

      In the “Links to Resources” part of Clot Connect’s website you will find a section: “Find a Health Care Professional”.

      5. “Anyone else think that they should monitor young women on the potential side effects of hormonal birth control?”
      Women on birth control pills should know the symptoms of DVT and PE. They should also know their personal DVT and PE risk factors beyond the pill (obesity?, Smoking?, Family history of clots?). They should know the risk factors that increase the risk for DVT and PE (hospitalization, immobility, surgery, long-distance travel, etc.) and they should make an informed decision as to (a) whether the pill is right for them, (b) which pill is the best for them (risk for clots in highest with 3rd generation pills, less with 2nd generation pills, least with progestin-only pill or injections, not increased with Mirena IUD). And, most importantly: if symptoms of DVT or PE occur, the woman should consider that she could have a blood clot and seek medical attention. Routine screening with a Doppler ultrasound or blood tests to “discover clots before they cause symptoms” would not be useful.

      • Em says:

        Stephan- Thank you so much for your helpful comments and advice. I truly appreciate the time involved in your reply— I hadn’t realized there was a website connected to this blog, I’m going to do what I usually do first and read up on the information already posted here!

        I agree that women on birth control pills should be aware of the symptoms… at least, I’m aware now. When I was originally prescribed the Pill they told me, “This will help with your acne, your mood swings– and, as a bonus, you won’t get pregnant!” They never mentioned potential side effects. I hope that this has changed with doctors today, and that they take time to make sure that “invincible” teenagers understand the risks.

      • natalie says:

        Along the lines of refraining from hormonal birth control / other HRT for those with previous clots due to birth control pills / pregnancy, is there any known reason to also refrain from soy products such as soymilk, edamame, etc.? Do the estrogen-mimicking properties of soy affect clotting the same way as estrogen does?

  6. Foo says:

    Thank you for this hugely helpful article. This should really be a hand-out for patients who have suffered a thrombus and are wondering about their future on anticoagulants!

  7. Amy says:

    You rarely have mentioned my thrombophilia which is elevated factor VIII. What can you tell me of long term anti-coagulation treatment after a very extensive unprovoked CVST?

    • Stephan Moll says:

      Elevation of factor VIII is a risk factor for a first clotting event. However, it is not clear whether it predicts recurrence of clots – published data have been inconsistent. Thus, factor VIII levels are NOT a helpful tool to decide how long a patient with a clot should be treated with blood thinners. Because of the lack of clinical utility I barely ever test a patient for factor VIII levels.

      For a discussion on length of anticoagulation after a cerebral and sinus vein thrombosis, please see

  8. Michele Walker says:

    Excellent information on this topic. My hematologist recommended I remain on Coumadin for life, but my ortho surgeon thinks it is “over kill”. While I am heterozygous Factor II, my DVT occurred after two “back-to-back” ankle surgeries within two weeks of each other. My reservation regarding long-term anti-coagulant therapy is based on the fact that while the Factor II might have contributed to my DVT, I still think it was the ortho surgeries than played the bigger role in triggering it. I’ve lived 45 years with no DVT and suddenly the Factor II aspect caused me to have a DVT? Hard to believe other factors didn’t play a part. However, since my ortho condition is reoccurring and I am facing possible surgeries in the future, I don’t know if it’s wiser to stay on the Warfarin or not. I really do like my hematologist and I think she’s a knowledgable and compassionate doctor. She said herself, though, that she tends to lean toward being cautious in treatment options. After reading all of this, it really makes me wonder if I should get a second opinion. I don’t mind being on anti-coagulants if I need to, but don’t want to if it isn’t really necessary. Will have been on Warfarin for 2 years in January 2012.

  9. Jeff says:

    This is a great site, thanks for all the information. I’m a little confused and would like your opinion regarding length of coumadin treatment in my situation. I trained all summer and ran a marathon 10-9-2011. I had arthroscopic knee surgery 11-1-2011 for a torn meniscus. 11-7-2011 diagnosed with DVT in my calf (distal) and some superficial thrombosis. Treated with aspirin (325 mg daily) and serial ultrasounds. DVT resolved itself within 10 days. Taken off aspirin. 12-9-2011 diagnosed with DVT behind my knee (proximal). Treated with Lovonox injections(for 6 days) and coumadin daily. My Internal Med Doctor prescribed a 3 month coumadin treatment duration. After going on the Lovonox and coumadin, I had periodic episodes of light-headedness (no breathing issues). Light-headedness continued and Doctor recommended a CT scan. CT scan done 12-15-2011. Results were positive for 2 very small PE. After this Doctor prescribed 6 month coumadin treatment and to go see a Pulmonologist. Light-headedness continues. 12-28-2011 saw the Pulmonologist. He reviewed the CT scan however did not think it was a PE, rather, after conferring with another radiologist, concluded the ‘spot’ was just how the dye had ‘settled’ in the lung. Now I was back to a 3 month treatment from my Internal Med Doctor. 1-9-2012 went to another Pulmonologist. She looked at the CT scan and said that she sees the area that may be the PE. Regardless of conclusive PE, she recommended 6 month coumadin treatment.
    I am lightly excercising and experiencing some mild postthrombotic swelling and discomfort. I am still experiencing some periodic light-headedness. I am going back to my Internal medicine Doctor next week for a follow-up. My thought is to stay on the coumadin for 6 months and do another ultrasound prior to coming off the coumadin. What are your thoughts/recommendations? Also, is the light-headedness a side affect of the coumadin, or should I be looking for something else? Thanks

    • Stephan Moll says:

      1. Treatment for a popliteal (=proximal) DVT with or without PE is the same: 3 months of blood thinners [ACCP guidelines: Kearon C et al. Antithrombotic therapy for VTE disease. Chest 2012;141(2)(Suppl):e419S-e494S].

      2. Getting a follow-up ultrasound: Length of treatment decisions are independent of Doppler ultrasound findings. The reason to repeat a leg Doppler ultrasound at the end of the treatment with blood thinners is to get a new baseline, not to help with the decision how long to treat with blood thinners. Such a new baseline ultrasound makes it easier to interpret future ultrasounds, in case future new problems (new leg swelling or pain) come up.

      3. Lightheadedness: Unclear why they occur in this patient. It is not a known side effect of warfarin.

      • Jeff says:

        My Doctor wants to continue the Coumadin for 6 months, which I can understand. To help predict my chances of future clotting after coming off the Coumadin, what blood tests should I do now? And what tests should I do after coming off the Coumadin? Thanks again for sharing your knowledge.

      • Stephan Moll says:

        Factor V Leiden and II20210 mutation tests, as well as anticardiolipin and anti-beta-2-glycoprotein-I antibodies are reliable on warfarin, as is (almost always) the antithrombin activity test. Protein C and S activity are always low on warfarin and a patient needs to have been off warfarin for 3 or more weeks before one should test protein C and S activity. Lupus anticoagulant test may be falsely positive on warfarin, even though one would expect only a slightly abnormal test, not a full blown markedly abnormal results. D-dimer can be tested on and off warfarin, as discussed in the blog post. A very meaningful result is the one obtained once the patient has been off warfarin for 4 or more weeks.

  10. Emilie says:

    I was diagnosed with a provoked distal DVT (due to birth control) almost 6 months ago. Nearing the end of my treatment, I asked for another ultrasound to see if the clot is still there. It is. My Doctor maintained that I need to end my treatment of Warfarin after 6 months. I’m a little uneasy with this and even sought a second and third opinion by other Doctors. 2 to 1 they also suggested stopping treatment. One of my questions is “is it normal to stop treatment after 6 months if the clot is still there?” I was told by one Doctor that the clot may be there for the rest of my life; the other veins around the clot will compensate for the damaged vein. My other question is ” is this true? The clot may never dissolve?”

    • Stephan Moll says:

      How common is residual clot?
      Approximately 50 % of patients with DVT will have some chronic scar tissue in the veins where the clot was (often termed “residual clot”) – on ultrasound this is reported as “chronic occlusion”, “partial recanalization”, “chronic striation”, “chronic changes”, hyperechogenicity”, etc. It reflects that in a number of people the clot does not resolve completely. There is nothing a patient can do about that and clinically it may not be relevant. What counts is whether the patient has clinically recovered, i.e. does he/she have any symptoms of postthrombotic syndrome. Many patients with residual clot are without symptoms and, vice versa, a number of people with clear veins at the end of the warfarin treatment have left over symptoms. The residual clot is old, chronic, scar tissue in the veins. It does not break off and does not pose a risk of PE.

      Does residual clot increase the risk of recurrent clot?
      The key question is whether patients with residual clot have a higher risk of recurrent clot if they come off blood thinners. A recent meta-analysis [Carrier M et al. Residual vein obstruction to predict the risk of recurrent venous thromboembolism in patients with deep vein thrombosis: a systematic review and meta-analysis. Journal of Thrombosis and Haemostasis, 9: 1119–1125] showed that residual clot is (a) associated with a mildly increased risk of recurrent DVT once blood thinners are stopped in patients who have had a DVT (unprovoked and provoked), and (b) not a predictor of recurrent clots in the subgroup of patients with previous unprovoked (idiopathic) DVT.

      Should patients with residual clot be treated longer with blood thinners?
      No. Length of treatment decisions are independent of Doppler ultrasound findings. The reason to repeat a leg Doppler ultrasound at the end of the treatment with blood thinners (typically after 3-6 months) is to get a new baseline. This makes it easier to interpret future ultrasounds, in case future new problems (new leg swelling or pain) come up.

      How long should a patient with distal DVT be treated with blood thinners?
      3 months is the recommended length – see brand new ACCP guidelines [Kearon C et al. Antithrombotic therapy for VTE disease. Chest 2012;141(2)(Suppl):e419S-e494S].

  11. tina will says:

    I would like to know if my daughter should have been told more about her condition-OR IF THEY SHOULD HAVE DONE MORE.
    TWO years ago she developed a blod clot in her lungs after being on birth controll.they proceeded to put her on blood thinners for a year,after the year she was told as well as i that she was fine.we never knew this could happen again.8 months ago she went into the hospital(same one that treated her for pe)complaining of shortness of breath,sharp pains in her chest and legs.they Ran some tests,found nothing and sent her home.on jan 13th ,2012 my daughter walked into a grocery store and collapsed-they could not revive her she had a blod clot hit her lung.never did we know this could happen again-we thought it was because of the birth controll only and she stoped them long ago.we were never told aspirin could help daughter was a big girl-obese but also had a big heart-i felt we were not told enough…was my daughter wronged?

    • Stephan Moll says:

      A patient with PE (or DVT) associated with birth control pills is often treated with 3-6 months of warfarin and then taken off, because the majority of patients will not have another clot and long-term blood thinners carry a risk of serious bleeding. However, it is known that these patients have some risk of a second clot – approximately 8 %, i.e. one of 12, develop another clot over the following 3-4 years (Cushman M et al, 2006). There are some risk prediction tools to determine which woman with hormone-associated clot is at higher risk for recurrence and which woman at lower. This will eventually hep determine which of these patients might benefit the most from staying on blood thinners long-term, and whose risk of recurrence is so low, that discontinuation of blood thinners is appropriate. However, none of these tools has been well established – i.e. none of them is validated. Two of these scores – the HERDOO-2 score and the DASH score – are discussed on Clot Connect elsewhere (; page 3, section C.b.).

      Whether Aspirin is effective in preventing clot recurrences in women who had a birth control pill associated DVT or PE is not known. Data presented in December 2011 that aspirin may have a positive effect in preventing some recurrent clots in patients with unexplained DVT or PE needs to be fully published and needs to be repeated, to show that this beneficial effect is truly there before it can be accepted as clear-cut, that aspirin has any beneficial effect in preventing DVT or PE recurrences. The aspirin issue is further discussed on Clot Connect at; page 1, section A..

  12. Binyam says:

    I was diagnosed with a massive PE on both sides of my lung in late 2010, all the risk factors were assessed and they turn out to be negative. The only thing which is bugging me is that I have donated plasma about 9 times in a a 7 week time period in early 2010 and I was told in the process I was being given a blood thinner to prevent the blood from clotting while separating the plasma. Is there any study or evidence which shows an introduction of a blood thinner into a rather healthy individuals increases their risk of having a blood clot ?????

    • Stephan Moll says:

      The only way I could imagine a clot would happening in such a circumstance is if the plasma donor received the blood thinner heparin and then developed heparin induced thrombocytopenia (HIT) – HIT is often associated with a temporary decrease in blood platelet count and a positive HIT test. However, now, more than a year later, the platelets and HIT test would be expected to be normal/negative again. Worthwhile to discuss the HIT issue with your doctor, though.

  13. Deana says:

    My husband had a large PE on his right side and smaller ones on his left side in August. He was in hospital 1 week and has been on Warfarin since. There was no known cause. His Father’s family of 12 had 9 members with clots and 2 cousins have had clots. The tests for genetics and other causes have been negative. He is 43 a non-smoker and active. Now the question is whether to stay on Warfarin or not.

    • Stephan Moll says:

      1. The issues that go into the decision making as to how long somebody like your husband might have to be treated with blood thinners are adressed in detail in the above “DVT and PE: How Long to Treat with Blood Thinners” blog entry.

      2. Regarding strong family history of clots: Your husband and his family might want to consider particiapting in a genetic study: I would encourage him.

  14. Erv says:

    What a wonderful site.

    I am scared to death at the moment. I had a DVT last Saturday (2-24-12). It traversed my entire leg, top to bottom. I am 58, ideal body weight, run 4-5 times a week (4-5 miles), lift weights, eat a pretty healthy (ex dietitian), don’t smoke, but drink 4-5 beers a night. No family history of DVT.

    My General Practitioner cannot say why I developed it, but days before I did extremely heavy work cutting trees and moving rocks. Doing so I generally get a few leg burses. I did get slightly dehydrated, because I forgot to take water with me.

    My doctor wanted to put me on Coumadin, but I have many friends on it and they all say they suffer from side effects. He opted for Pradaxa. I am scheduled to see a Hematologist this Thursday.

    Like many here I really do not want to be on blood thinners, but I see I may have to for some time. I do have one question about blood thinners.

    When I turned 50 my doctor said it would be a good idea to take a baby aspirin daily. I did for a few months, but every time I got the slightest cut, I bled a lot. So much I decided to get off them.

    If aspirin seemed to be so effective in making me bleed freely, then why is aspirin not a possible choice?

    I have printed out this page and plan to take it with me to the Hematologist and doctor on my next visit.

    I want to get back to running as soon as it is safe and get off the blood thinners as well.

    Thank you for all the great information.

    • Stephan Moll says:

      Aspirin is not very effective in preventing DVT or PE from getting bigger or recurring. Increased bleeding while on aspirin from a skin cut does not translate to decreased clotting in blood vessels (in veins) in the body.