Vitamin K vs. Blood Clots

I keep getting conflicting information on the advisability of taking large amounts of Vitamin K. I am taking 2100 mcg (1000 K1, 1000 K2-as menaquinone-4). My Endocrinologist tells me to stop taking it because of the risk of blood clots, but what I'm reading on the Internet says, as long as one is not on any blood thinners (such as Coumadin), there is no risk. I also know that there is confusion around the units of measure. I believe you need 1000 mcg to equal 1 mg. So, I think that has also been a factor in the confusion. Can anyone address this?

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Hey RuRuMe, I had to avoid supplements and foods with Vitamin K when I took a daily anticoagulant (Coumadin). Now I take a daily multi with K and can eat all the veggies that are high in V-K, therefore eating green veggies daily especially Cole slaw.
I have not read any data stating V-K could cause blood clots in any part of the body.

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Hi RuRuMe, I had a blood clot last year from Reclast and am on Coumadin (a blood thinner). I was told that vitamin K helps to thin your blood out. My diet has always consisted of a lot of salads, broccoli, spinach which all contain Vitamin K (green leafy vegetables). My doctor kept checking my blood and changing the Coumadin until I was at a good level and enjoying things that I like. In the hospital, they said to stay away from a lot of green leafy vegetables. As far as the measurements, mcg versus mg; I don't have an answer for that. I hope this may help in some small way. Good luck to you.

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Hi LovetoCrochet, Actually Coumadin can Kill you because it works against Vitamin K2 and allows calcium to build up in arteries etc Check it out........ Sounds like your doctor has been doing the balancing act so you can get K2 in your diet and still get what he/she feels is the necessary amount of Coumadin...... Phil

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Hi RuRuMe, I went to a hematologest (sp) and he indicated no problem with taking 100 mcg of K2 seems (even with my stent) .... on Dr Mercola's website a leading researcher on K2 Dr Vermer (sp) recommended taking 180 mcg.......could be mistaken could be mg but that sounds like way too much mgs I experienced a significant difference between taking 50 and 100mcg in terms of Heart Ca Thunking.....Phil

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LovetoCrochet said: "I was told that vitamin K helps to thin your blood out."

Vitamin K is a coagulant -- the opposite of thinning out your blood. My cousin, who is a doctor, has concerns about my taking K2...but so far I'm continuing to take it with the thought that I took Evista for years, which also has a warning about blood clots.

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RuRume, you mean you are preferring info from the internet over your dr? hmmm. I guess you mean studies etc not people yapping their thoughts? I take 40 mcg and have read not to take more unless there is a specific indication and it is monitored. My dr advised against it for clots, similarly evista for clots- but that may have been my personal advice based on my records. That is why randomly following someone elses presciption routine is not a good idea.

The thing with this board is we dont always hear when someone went nutso with supplements or something and ended up in the hospital or morgue. we just go and read the next post, you know? 1 or 2 people trying something out does not a study make, you know?

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Thank you all for your comments. Here is some more information on Vit. K gleaned from the Internet. (And, Chalk, you'll see that these are all referenced). My questioning of my Endocrinologist stems from the fact that doctors typically are not well versed in diet, nutrition and supplementation. They normally study diseases and interventions, not prevention and holistic treatment approaches to healing.

This is from the Univ. of Colorado: "Increased risk of fractures or reduced bone density may result from inadequate intake of vitamin K, due to its necessary role in production of bone proteins such as osteocalcin. Several clinical trials have supported the proposition that, in certain situations, vitamin K supplements enhance the integrity of bone. In seems clear that use of vitamin K antagonists like Warfarin for purposes of anticoagulation have toxic effects on rapidly-growing bone."

This is from Wikipedia, but it too comes highly referenced: "Recommended amounts
The U.S. Dietary Reference Intake (DRI) for an Adequate Intake (AI) of vitamin K for a 25-year old male is 120 micrograms/day. The Adequate Intake (AI) for adult women is 90 micrograms/day, for infants is 10–20 micrograms/day, for children and adolescents 15–100 micrograms/day. In 2002 it was found that to get maximum carboxylation of osteocalcin, one may have to take up to 1000 μg of vitamin K1.[49]


Although allergic reaction from supplementation is possible, there is no known toxicity associated with high doses of the phylloquinone (vitamin K1) or menaquinone (vitamin K2) forms of vitamin K and therefore no tolerable upper intake level (UL) has been set.[citation needed]
Blood clotting (Coagulation) studies in humans using 45 mg per day of vitamin K2 (as MK4)[25] and even up to 135 mg/day (45 mg three times daily) of K2 (as MK4),[50] showed no increase in blood clot risk. Even doses in rats as high as 250 mg/kg body weight did not alter the tendency for blood-clot formation to occur.[51]
However, a synthetic form of vitamin K, vitamin K3 (menadione), is demonstrably toxic. In fact, the FDA has banned this synthetic form of the vitamin from over-the-counter supplements because large doses have been shown to cause allergic reactions, hemolytic anemia, and cytotoxicity in liver cells.[52]"

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Here's what I just now received (in answer to the same question I posed to them) from The Wellness Letter, which is a Univ. of California, Berkeley, health newsletter:
"To help keep your bones strong, eat foods rich in vitamin K, such as broccoli, spinach, kale, and other leafy green vegetables. In a recent Spanish study in the journal Bone, older people (average age 67) who consumed the most dietary vitamin K had higher bone mineral density than those with low intakes. And those who increased their intake of the vitamin over a two-year period tended to have less bone loss. Previous studies have found that K supplements can improve bone quality and reduce fracture risk, but you’re better off getting it from foods, which contain other bone-healthy nutrients. Vitamin K can interfere with the anticoagulant warfarin (Coumadin), so if you take this drug, talk to your doctor about howmuch K is safe to consume."

It's best to get K from food, and is a worry only if you're on a blood thinner.

Michael Goldman

Wellness Letter

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Hi RuRuMe,

Please see the following articles for additional info. on the subject:

Excerpt: " ... Although vitamin K does assist the body in clotting blood, however, it does not cause the types of blood clots that block normal blood flow.
Physiology of Blood Clotting

Your blood contains red blood cells and blood cell fragments, called platelets, which circulate in a liquid called blood plasma. In addition to blood cells and platelets, your blood also contains a number of substances called clotting, or coagulation, factors. When you damage a blood vessel, these clotting factors allow platelets to stick together and form a blood clot at the site of blood vessel damage. This blood clot stops bleeding and allows the wound to heal. Vitamin K ensures that the clotting factors in your blood work properly. . . .
Abnormal Blood Clots

Although vitamin K does allow blood to clot normally, it is not a factor in the formation of abnormal blood clots. Blood clots that block blood flow can occur as a result of a number of underlying medical conditions, including atherosclerosis, deep vein thrombosis, heart arrhythmias, family history of blood clots, medications, peripheral artery disease, prolonged bed rest, stroke and surgery, according to the Mayo Clinic."

And, per Dr. Mercola ... " Vitamin K Prevents Arterial Plaque & Heart Disease"

Vitamin K helps to prevent hardening of the arteries, which is a common factor in coronary artery disease and heart failure. Research suggests that vitamin K may help to keep calcium out of artery linings and other body tissues, where it can be damaging.

ref. t-two.aspx

More importantly, Dr. Mercola said..." Vitamin K is sometimes referred to as the “forgotten vitamin” because its benefits are often overlooked. It was named after the word “Koagulation,” to reflect its essential role in blood clotting. In fact, the enzyme nattokinase—derived from natto—is safer and more powerful than aspirin in dissolving blood clots, and has been used safely for more than 20 years." ref. e-your-health.aspx

btw, Yes, 1000 mcg = 1 mg

And, the dosage for vitamin K depends on which type. For example, the Super K by Life Extension has (in one softgel):

Vitamin K2 MK7 100 Mcg
Vitamin K2 MK4 1000 Mcg
Vitamin K1 1000 Mcg
Vitamin K Activity 2100 Mcg

Hope the above articles add to your awareness and help in your decision. Vitamin K is still rather new and I believe that it's really an important vitamin. However, I also believe in moderation and be conservative in taking any supplements.

<3 Sylvia * * * * *

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I recommend reading Lara Pizzorno: "Your Bones" for an excellent review of Vitamin K1 and K2. Writers sometimes muddle the two forms of Vitamin K so it is little wonder that consumers are confused.

My expertise is in research evaluation with a special interest in Alternative methods for treating osteoporosis; therefore I reviewed Lara Pizzorno: Your Bones carefully and critically. Specific issues such as Vitamin K1 and K2 are clearly explained for the lay reader. For example Vitamin K2 in the form of MK-7 is effectively used (prescribed) in Japan for the prevention and treatment of osteoporosis.

The danger of jaw necrosis with bisphosphonate drugs is clearly explained. This book is research-rather-than-opinion based. For example she reports that as of 2010 there are more than 1,100 articles discussing bone death related to bisphosphonate use in peer-reviewed medical journals. Beware of bisphosphonate drugs if there is a possibility for a tooth implant in your future.

Strontium Citrate (supplement) and Strontium ranelate (prescription Protelos) are both discussed in detail.

"Your Bones" is a valuable resource for consumers and practitioners.

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Thank you all for your great comments. I'm also perplexed that the Super K by Life Extension that Sylvia mentions -- which is what I have -- provides 1000 mcg of MK-4, but only 100 mcg of MK-7. Why would this be the case if what Sarah relates about MK-7 being used in Japan to treat Osteoporosis is true? Why wouldn't Life Extension give us more MK-7 then? It's as if all these experts who do this type of research don't read each other's research because no one seems to recognize or report on all these discrepancies.

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Excerpt from Bone Health by Lara Pizzorno:

MK-4 is produced synthetically. It has a half-life of only 1-2 hours; therefore larger doses are needed in divided doses.

MK-7, a natural compound derived from natto is well absorbed and as little as 45 micrograms per day has been found to activate sufficient osteocalcin for bone health.

William Faloon's article "Protection against arterial calcification..." published by Life Extension is an excellent article but I believe that Bone Health by Lara Pizzorno provides extensive explanations that can not be covered in an article.

Sara DeHart (2011) "Bone and cardiac health: Are Vitamins K1 and K2 the missing links to the epidemic of osteoporosis and arterial calcification" also is a resource on this topic.

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Ah, even more confusion! :)

The MK-4 version of Vitamin K2 is the one produced naturally by humans and used by mammals. MK-4 is the most effective Vitamin K2 for bone loss since it adjusts osteoblast activity in humans which MK-7 doesn't do. The MK-4 sold is both identical to what your body makes and is made synthetically since this is the easiest means of production. While MK-4 disappears from the blood quickly, usually within several hours, this may be a positive aspect of the body actually using MK-4 faster and better than MK-7.
To my knowledge, the treatment for bone loss and heart disease in Japan uses 15 mg (equal to 15,000 mcg!) of the MK-4 Vitamin K2 three times a day. Most scientific research has been done with the MK-4 variety as a natural component of human chemistry.

The MK-7 variety of Vitamin K2 is natural to the bacteria that produce it, but it only gets into the human body from outside sources. Much but not all of its chemistry in the body is similar to that of MK-4. It is known to be stimulating to the nerves and brain in amounts of 100 mcg to 200 mcg and larger. Natto can have from 800 mcg to 1300 mcg of MK-7 per serving! MK-7 appears to strongly prevent certain virus caused liver cancers which were not noticed in results with MK-4.

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Although you can induce bleeding by extreme Vitamin K deficiency, Vitamin K and K2 have nothing to do with normal blood clotting levels. They do participate in blood clotting chemistry so doctors talk about Vitamin K only if they are giving Coumadin which intentionally wrecks the clotting chemistry that Vitamin K participates in. If the blood clotting chemistry is already working 100%, there is no possible way to get more clotting out of a process that is 100% complete. So taking large amounts of Vitamin K2 is safe and has been observed as such in research giving 45 mg and even 90 mg of Vitamin K2 daily.

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There is a detailed overview of research in Vitamin K2 including references.

They include the statement:

"Side Effects and Toxicity
From a large number of clinical trials using
dosages in excess of 40 mg/day, there were no reports of
side effects associated with any type of hypercoagulable
state.26,38,39,41 Both animal and clinical studies support
the conclusion that vitamin K2 has no abnormal hemostatic
activity. In one study, vitamin K2 given to rats at
a dose of 250 mg/kg body weight per day for 10 days
resulted in no appreciable change in blood coagulation
characteristics or platelet aggregation.40

In a clinical study, 29 elderly, osteoporotic patients
were given vitamin K2 (15 mg three times daily,
30 minutes post-meals) for 12 weeks and monitored
for any change in hemostatic balance. After 12 weeks of
administration, all hemostatic markers remained within
normal range.38 In another study, examining the effect
of vitamins K2 (45 mg/day) and D3 (1 mcg/day) on
BMD in postmenopausal women, hemostatic measures
were also examined. Increases in both coagulation and
fibrinolysis were noted, but remained within normal
range and in balance, with no adverse reactions observed.

In another 2002 test conducted with both Vitamin D3 and Vitamin K2 Japanese researchers noted an increase in vertebral bone mass of 7.89% over 24 months without any coagulation problems. (These are typical elderly patients)

Experts and scientists do read each others peer reviewed research. Here you can find a published letter complaining that bone research is being run without the benefit of the 2002 research in Japan on Vitamin K2.

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Your detailed, well-referenced accounts are truly a breath of fresh air, Tango02!!! Guess I'll start taking my Vitamin K again. With all of this data, I wonder why those doctors who purport to specialize in Osteoporosis are not staying abreast?! Thank you so much for all this information!!!

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I also take K2 or Super K for my osteoporosis. I also take meds for hi b/p. Does anyone know for sure if I should continue taking it along with my Strontium ( I do not take it at the same time). I do take the Super K same time as Ca and Boron Chelate.

If I am take b/p meds and take Super K should that be a factor in whether I take the K or not?

Thanks for any help.


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I believe vitamin K lowers the clotting time (INR). My wife is on warfarin due to strokes, and the clinic cautions about overdoing the k in the diet. As long as she eats about the same amount consistently, then they can regulate the INR okay. I believe fishoil has the opposite effect.


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Ruru, do you follow Dr. Mercola's natural health care information? He has one here that you can read and listen to:

This link references studies which have used doses in mg vs. mcg. It also is a good reference when thinking through what may be right for a given individual:

I don't take large amounts of K or K2. I use Alive Daily Energy for my multivitamin. It has only 25 mcg of K. I also take K2 (MK-7) in 90 mcg from Jarrow Formulas or 100 mcg from Swanson. I always take the K2 with magnesium and calcium citrate and D3. We don't know long term what the effects may be from high doses of many supplements. They have found that Vitamin D3 is needed in much higher doses than thought. I take around 5,000 / day of D3. Due to a gluten sensitivity, I have not been showing enough in my blood. So, I'm trying to get off gluten.

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Tom-WI, you are absolutely right. They told me to be consistent about eating green vegetables. My levels have been good each time; at first it took a while to get the level between 2 and 3. I don't overdo it on the vegetables, but I just like them. Thank youl.

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