Vitamin K and Coumadin – What you need to Know.

Categories: News

Article by Laura Earl, RN, BSN, CACP

If you have been diagnosed with a blood clot, a medication named warfarin (Coumadin) may be prescribed as part of your treatment to prevent further blood clots. You may need to take warfarin (Coumadin) for a few weeks, months, or the rest of your life. While taking warfarin (Coumadin), there are a few things about vitamin K you will need to know.

What is vitamin K?

Vitamin K is a naturally occurring vitamin.  Vitamin K is primarily found in leafy green vegetables such as spinach, broccoli, and lettuce, and enters your body when you eat these foods. Vitamin K is produced by the bacteria in your intestines, and it is also in vitamin and nutritional supplements. Your body uses vitamin K to produce some of the clotting factors that helps blood clot.

How does Warfarin (Coumadin) work?

Warfarin (Coumadin) works by interfering with how your body uses vitamin K.  The metabolism of warfarin (Coumadin), vitamin K, and vitamin K dependent clotting factors takes place in your liver.   Warfarin (Coumadin) prevents the production of vitamin K dependent clotting factors.  As a result, clotting occurs at a much slower rate.  One good way to think about vitamin K and its importance while taking warfarin (Coumadin) is that you need to maintain a balance between the amount of vitamin K in your body and the amount of warfarin (Coumadin) prescribed by your healthcare provider.

What do I need to know about Vitamin K, if I am taking warfarin (Coumadin)?

Changes in the amount of vitamin K in the diet can alter the metabolism of warfarin (Coumadin ®).  However, vitamin K does not influence the action of other blood thinners, such as heparin or low molecular weight heparins (Lovenox ®. Fragmin ®, or Innohep ®).

You should aim to keep the amount of vitamin K in your diet consistent.  For example, if you normally eat two servings per day of food that is high in vitamin K content, you should continue this pattern every day.  If you do not normally eat foods that are high in vitamin K, do not suddenly eat a large amount of them.

There are certain things about vitamin K that you cannot control.  For instance, some medications and illnesses (intestinal diseases and/or infections) can lower the amount of vitamin K in your body or change how your liver metabolizes your warfarin.

Can vitamin K affect my INR?

Yes, your INR refers to the international normalized ratio test, a standardized way to measure how your blood is clotting.  The lower your INR, the more quickly the blood clots or the “thicker” the blood.  The higher your INR, the longer it takes the blood to clot or the “thinner” the blood, putting you at risk for bleeding problems.  With an increase in vitamin K , your INR level may drop.  Conversely, a decrease in vitamin K intake may increase the INR.  Other things, like medications, antibiotics, and herbal products may also influence your INR.

What should I tell my anticoagulation healthcare provider?

Any time your vitamin K intake changes, it is important to notify your anticoagulation healthcare provider.  Some of the circumstances that may apply include if you:

  • Start taking a multiple vitamin or other vitamin supplement that contains vitamin K (such as Viactiv ®).
  • Use a nutritional supplement such as Boost ®, Ensure ®, Glucerna ® or SlimFast ® – shakes or nutritional bars.
  • Increase or decrease the amount of leafy green vegetables you are eating (refer to the USDA website at
  • Start or stop drinking V8 ® juice.
  • Develop an illness, including a respiratory infection or gastrointestinal flu that changes how well you are eating. Have lifestyle changes or emotional stress such as illness, the death of a family member, travel, or even seemingly simple things like moving or remodeling your home

You do not have to avoid foods or other products that are high in vitamin K; these foods have many other vitamins and minerals that are part of a healthy diet.  The most important thing to remember about vitamin K intake is being consistent as much as possible and communicating any changes that may occur to your anticoagulation healthcare provider.


The National Blood Clot Alliance (NBCA) and its Medical and Scientific Advisory Board (MASAB) do not endorse or recommend any commercial products, processes, or services. The views and opinions of authors expressed on the NBCA or MASAB websites or in NBCA or MASAB written materials do not necessarily state or reflect those of NBCA or MASAB, and they may not be used for advertising or product endorsement purposes.

It is not the intention of NBCA or MASAB to provide specific medical advice, but rather to provide users with information to better understand their health and their diagnosed disorders. Specific medical advice will not be provided and both NBCA and MASAB urge you to consult with a qualified physician for diagnosis and for answers to your personal questions.

Posted November 24, 2008

Return to our News Page


Author: admin

26 Responses to "Vitamin K and Coumadin – What you need to Know."

  1. Georgia Huenefeld
    Georgia Huenefeld Posted on January 22, 2014 at 12:54 am

    Has any alternative physician or group come up with an anti-bloodclot diet that works without prescription drugs? I’m on warfarin and wonder if I could learn how to balance my diet and skip the anti-coagulant.

    • Vicki
      Vicki Posted on March 24, 2014 at 3:11 am

      You don’t know me or how much I want off this stuff as well – however, I know the only thing that could possibly end this atrial fib is an ablation, and I don’t think I’m ready for that yet.

      • Andy
        Andy Posted on April 23, 2014 at 5:22 pm


        Over 12 years ago, was diagnosed mild hypertension 140 over 90 and was given a beta blocker, Metoprolol. Within a month, I began having afib attacks, Mild at first, progressing to severe to the point I landed up in hospital several times. I was put on Coumadin but within 2 weeks, my INR spiked so high the doc took me off of it.

        The afib attacks continued and got worse and worse. Many times, it was so bad I thought I would die. So bad all I could do is squat on the bed and rock back and forth till the attack passed some 4 to 6 hours later. It took 2 years to get to that point. I would get 2 to 3 attacks a week. Thinking it was stress, I quit my job. That didn’t help.

        Doing research on the Net, I came across some references that beta-blockers can provoke arrhythmias in some people. I took that info to my doc but he insisted there was no connection.

        Nevertheless, I weaned myself off the Met over a period of 2 weeks and the result was that my afib attacks stopped and I was free of them for 5 weeks. This from 2 to 3 per week before, on the Met. Horrified, my Doc insisted that I go back on the Met. I took ONE dose and within a few minutes, I got an afib attack. And, from there, despite not taking any Met anymore, the attacks resumed.

        More research led to a study by the Mayo Clinic that magnesium had an anti-arrhythmia function. So I began taking Magnesium supplements and increased the daily dose from 250 milligrams to 2000 milligrams, in divided doses. That was my upper limit as any higher and it gave me the runs.

        At the same time, I avoided the triggers of an attack. I ate half as much, twice as often, smaller meals, NEVER stuffed myself. NO alcohol. NO spicy food. I began wearing track pants full time, no pressure of a belt across the stomach.

        Within three months, the attacks stopped and I was free from them for 5 years. More on that later.

        Here is how I think was going on. If you cut out a piece of heart tissue, it would pulse at some 80 beats per minute. That’s automatic, that’s what keeps you alive when in a coma. That is the first heart rate control. When your heart needs to beat faster, as when you exercise or your fight or flight response is triggered, your body produces adrenalin and that raises your heart rate. When you stop the exercise, your vagus nerve goes to work to lower your heart rate to normal.

        These three mechanisms work together in balance.

        Metoprolol, a beta-blocker, interferes with the normal, adrenal function. This imbalance can provoke arrhythmias in some people.

        I spoke of all of this with a local gastroenterologist and I posited this theory. MY attacks were a result of stomach stimulation, feedback through the vagus nerve, back to the heart. The vagus nerve is a master nerve of sorts that has branches from the brain, through the spine to all organ systems, including the stomach and the heart. The gastroenterologist agreed with me that I was on to something, My regular Doc also, finally agreed that I was right.

        For 5 years, I kept a modest, maintenance dose of 250 milligrams of magnesium per day and had no problems.


        One summer I took up berry picking. By then I was wearing normal pants with a belt. After 4 consecutive days of berry picking, I had my first afib attack in 5 years. The belt pressing against my gut was the trigger. From there, I started to have regular attacks again.

        So the gut theory proved out. And once again, my strategy for stopping the attacks worked, only it took longer, the second time around.

        So, this might be something for you to consider. Just start taking 250 milligrams of magnesium, the citrate version is most effective, that is, magnesium citrate. Avoid all triggers related to the stomach. You know,, for me, a strong cough or sneeze or even a “belly” laugh would sometimes provoke an attack. Again, the stomach is involved. OR AT LEAST IT WAS FOR ME. But even so, the literature refers to post-prandial (after eating), the Valsalva maneuver that can either provoke an attack or stop one. Often, I found that if an attack was starting, if I tightened my gut and held on, the attack would sometimes abort.

        Do some research on the Net with the above in mind. Spend an hour a day. Ask Google, phrasing the questions differently. Read, read, read and save articles that may offer you some insight into what I am saying.

        I too was headed for ablation or even the maze procedure. This is open heart surgery, they put criss cross cuts on your heart and the scar tissue stops the erratic signals from doing their nasty. It works, apparently, but a few dollars worth of magnesium and attention to triggers worked for me without the risk and expense of surgery.

        Telling your doctor about this is up to you. In my experience, some react negatively and some are intrigued and have an open mind.

        Good luck, I truly hope it works for you.

        • Ray
          Ray Posted on May 14, 2014 at 5:09 pm

          You have really done your homework, just wondering if you could take a minute and see if you think my thinking is on the right track…
          Up till 1 year ago, never had any health issues, then all of a sudden couldnt breathe , thought I had pneumonia
          Was admitted to hospital for a week,
          Was put on coumadin, lasix, spironolactone digoxin, ( later took me off digoxin) one thing i have is And always have been is chronic constipation, have to take miralax with prune juice every day. I think that this is what caused my afib, constant straining…
          My afib has stopped, but i want to stop taking all the other meds,too..any comments?

      • Jae
        Jae Posted on February 4, 2015 at 5:20 pm

        My husband had an ablation in 2005 in the DC area and it didn’t work. After dealing with being on medication for his A-fib for 4 more years, he wanted another because he hates taking medication. We now live in Florida and he did extensive research to find someone that strictly did ablations. He found Dr. Pinski at the Cleveland Clinic in Weston Florida and had his second ablation in 2009. He was told that the first ablation didn’t enter the heart but treated the arteries outside of the heart, which didn’t do anything for his chronic A-fib. Dr. Pinski “fixed” his problem and he now has been off of ALL medication since November 2009. If you find someone that knows what they are doing, it’s worth the out patient procedure. His life has totally changed!

  2. […] Vitamin K and Blood Thinners – What You Need to Know (article via NBCA) […]

  3. Gayle
    Gayle Posted on March 25, 2014 at 3:35 pm

    I have a question, I’m in bed most of the time. I have failed back syndrome surgery, and my pain is so excruciating, I just stay in bed w/o exercise. I also have Osteoprosis and semi acute fractures different places in my body. I’m taking vit. K2 w/other vit.s w/D3 and calcium and magnesium. Is this combo of vit.s helping so I don’t get clots, while helping my brittle bones?

    Please help me, I’m very mis – informed…… Thank you and may God bless you.

    • April
      April Posted on October 24, 2014 at 3:58 am

      Gayle, I’d think about looking into a pain specialist and look into getting an intrathecal pump placed. (like a low dose constant epidural of multiple meds that’s implanted). It can be expensive, but it also can give you your life back. It works best for people with failed back surgery syndrome. lots of people have no more pills to take anymore (or a lot fewer) and can have more of a life from better pain control and not having so many opiates in your entire system.

      I think the vitamins probably don’t do much for clot prevention. But there may be some easy things you can do to help with that.

      Best Wishes – April

  4. Rachel
    Rachel Posted on April 23, 2014 at 9:46 am

    im on warfarine for life and i have got factor five lien.Being on warfarine for a long time Wil it cause my any harm .

  5. Mandy
    Mandy Posted on September 10, 2014 at 4:23 pm

    I need a diet that works with warfrin?

  6. Lynda
    Lynda Posted on September 22, 2014 at 4:01 pm

    my question is why does my INR spike for no reason, I eat no green veg, and only have liver every 3 months or so, Wed is was 7 so I stopped the coumadin for 2 days and Dr gave me Vit K, Friday is was down to 1.3, it has been as high as 11, I take 5mg a day except on Wed, anyone else have this problem? also anyone have Vit K at home to take in an emergency? (I have a 50 mile round trip to the Dr) thanks

    • Helen
      Helen Posted on October 4, 2014 at 2:33 pm

      I had an mi the end of May this year and have been on warfarin ever since. I have a consistent diet as far as my vitamin k intake is concerned and I am struggling to maintain an inr level of between 2-3. Have had regular spikes of 7+ and the most recent of 12.2. Had a 5mg dose of vit k and thankfully it bought it right back down. I am a chronic crohns sufferer and extremes of constipation and diareah so much so that I’ve to schedule an opperation to have a prolapse repair, having read the comments on here there seems to be a connection between gastro problems and the maintenance of a steady inr level. The docs I’m sure think I am messing with the drugs because they don’t want to take the time to properly investigate the spikes. This is a serious drug to be misused, and as I have various other medical conditions am insulted that they would think this. Has anyone else been made to feel this way?

      • jean
        jean Posted on March 19, 2016 at 11:59 pm

        I was told after my surgery, I would only be on warfarin until 6 months by the surgeon, when I was transferred to another hospital the GP said once I came off warfarin, I would go on 81mgs of aspirin, just a few days ago, he changed his mind without sending for an ultra sound told me I’m on warfarin for the rest of my life, according to what I have heard you are suppose to have a re-evaluation before continuing on with the warfarin, I asked him for such as that and the GP said it wasn’t necessary, I haven’t been able to eat much of the things I use to eat, they make me stomach sick.I don’t have any other serious medical problems, as I’ve been told by an internist.
        and yes doctors don’t seem to want to take the time and make sure you really need to take the warfarin, it is a serious drug to use, and it shouldn’t be used as just another prescription to pass on to the unsuspecting person. If you have a spike in gastro problems, the warfarin may not be the solution.. I take 5mgs of warfarin suppose to be for a blood clot which developed after a broken tibia of my left leg,, but I don’t have any more symptoms,like I had a first.So now I’m getting a female doctor who will listen and maybe understand why I want a re-evaluation to see if blood clot is gone and to test me to see if it will come back, if you don’t tell them you want a re-evaluation the doctor will continue to put you off, just tell him you will get another doctor who will listen.

    • Rosie
      Rosie Posted on November 3, 2014 at 7:16 pm

      I started having the same problem for about 3 months my inr was being checked weekly and was never within range.. It would be way too low or way too high, after talking to my Dr I explained everything that was going on in my life, she told me that stress and/or body pain was the cause of my inr jumping dramatically. I’m not sure if you are going through any new changes in your life that is causing depression, stress etc. I hope this helps(anybody).

    • flower
      flower Posted on November 20, 2015 at 7:56 am

      Mine spikes sporatically for no reason, too. Asked dr about getting my own machine which has helped to keep my levels under control. I check it or have it checked during office hours every two days or every other day, as needed. Can get info from Need an RX from a physician to begin it. Warning: The test strips are rather expensive, but worth the feeling of well being.

  7. josephine
    josephine Posted on April 22, 2015 at 4:07 pm

    i wll like to know if i ca still take wafarin whem i have menses

  8. Rachelle
    Rachelle Posted on April 25, 2015 at 8:50 pm

    My mother was told she had A_Fib,,it was a surprise to us as her regular doctors never picked up on it, for years.. She has never had a heart problem, yet they are filling her with Coumadin, Metropolol and every other drug known to man.. I do see the need for all this, in fact, I think it has made her worse. She was very active 3 months ago, now she is fearful to do anything. When is enough, enough?

  9. Dan
    Dan Posted on May 23, 2015 at 7:29 pm

    I’m a rookie to all this heart condition interactions. What I am not a rookie at is the use of quality pain management Doctors. My heart goes out to folks like Gayle that receive an answer from someone such as April that may be well meaning but have know idea of what the other is walking thru in life. God Bless you Gayle I hope you got some help. April , please refrain from passing judgement on others. Dan

    • George Householder
      George Householder Posted on February 23, 2016 at 7:37 pm

      I read April’s reply a couple of times, and have no idea how you came to the conclusion that she was passing judgment on somebody. I thought her response to Gayle was accurate and compassionate. I also wrestle with Coumadin (Warfarin), was in the clinic today getting my INR done (did it last Friday) because for some reason I can’t keep it in check. I have an artificial Aortic Valve and need to keep it between 1.8 – 2.5. Friday it was 1.1. I know everybody that wrote talked about high INR’s, they cause me to bleed and bruise, low INRs cause my heart to stop beating.

  10. Dian
    Dian Posted on February 25, 2016 at 10:57 pm

    I am on fragmin every day and still my inr fell heart looking into hughs syndrom…any one else have this problem….i also have RA….

    • Ellen
      Ellen Posted on June 8, 2016 at 1:50 am

      Dian: Hughes Syndrome is also called Antiphospholipid Syndrome (APS), or “thick blood.” I have found an APS support group on Facebook, through which I have gained a great deal of information on the syndrome, how to treat it, handle and cope with it. I have it , and it has caused me to have five strokes, migraines and a miscarriage. I have also learned through the group that if you are having difficulty getting control over an erratic INR while on Warfarin (the generic), have your doctor write a “brand (Coumadin) necessary” prescription.

      Best wishes,

  11. arlene bautista
    arlene bautista Posted on March 4, 2016 at 1:59 pm

    i am on warfarin coumadin for 5years now..but then still find difficult to balance still have bruises appeared on my different parts of my body and i have this heavy menstral problem

  12. jean
    jean Posted on April 9, 2016 at 4:00 pm

    I had a break in the tibia of my left leg and a dislocation same side. Had surgery april 6th 2015, blood clot developed in leg travelled to left lung. but all reports say it was a low level clot.
    surgeon said I would be taking warfarin for only three months. I was transferred to a hospital closer to my home, my family doctor recently told me I would be on warfarin the rest of my life, which dealt me a big blow. according to my records I was supposed to be re-evaluated to see if clot had gone, then the surgeon would wean me off the 5mgs of warfarin, but without a re-evaluation being done how can your doctor say your on this drug for life. The internists all say there is nothing else wrong, so why is this doctor keeping me on this drug.
    The foods I enjoyed, I can’t eat because they make me sick, I am afraid to do any form of exercise because the doctor has warned me about certain exercises and that I could bruise or bleed. I feel afraid to even go outside, or drive my car because of this. I want to take a trip to another Province in canada, but once again I’m hesitating because I’m afraid.
    I’ve asked for a ultrasound but he said it wasn’t necessary because I will still have to stay on the drug for the rest of my life, It is very hard to get another doctor because of the shortages of this province, I would prefer a woman doctor but can’t get one. what the heck do you do to get the results your looking for.

  13. JEFF
    JEFF Posted on August 12, 2016 at 6:42 am

    does alcohol thin or thicken blood ?

  14. I
    I Posted on September 2, 2016 at 1:52 pm

    After having a STROKE in my 50’s ,A Wonderful young Dr was determined to find out why!!!! He sent me for a lot of blood tests and I joked that I didn’t think I’D have any left !!! Well he called me and asked if I would have some more done & I said sure because if it was going to help I’D go right away !!!! I was so happy to get an answer what caused my Stroke!! We finally got an answer & we did for short it was ” APLS ” . Then it was what to do for it??? Because they did’t know!!!! Well I did some work on the answer !!! There is an organisation called ” N O R D ” that is so important ” NATIONAL ORGANISATION OF RARE DISORDERS ” !!! They had the answer: I called them and they told me that they’d send me the the information and in a few days I called my Dr & we were ready to get a good treatment going!! They had already put me on a small amou nt of ” WARFARIN ” because a Blood Clot spot was on my brain !!! My own body had started to cause my Blood Clotting! ! I I I have taken WARFARIN for 13 years & haven’t had aNY more blook clots ,following up ” INR cheched ” INR ” INR