For instance, here’s a question posted by a viewer on our YouTube channel.
Vitamin K is important as it is required for making blood thicken or “coagulate” to form a clot. If you’re wounded or get a cut, it is this clotting process that would stop the flow of blood.
However, vitamin K can interfere with a specific class of blood thinners called VKA (vitamin K antagonist).
What are vitamin K antagonists?
A vitamin K antagonist (VKA) is a special blood thinner. VKA reduces blood clotting by decreasing the action of vitamin K.
Among VKAs, coumarins are the most commonly used. And among coumarins, warfarin (sold under the brand name Coumadin and Jantoven) is the most popular.
The interfering action, however, goes both ways. VKA depletes the action of vitamin K. On the other hand, vitamin K also interferes with the blood-thinning action of VKAs (InnovixLabs, 2019).
What are blood thinners?
Blood thinners are medications or supplements that help blood flow smoothly. They don’t thin your blood or break up clots. They just decrease the risk of clots by slowing the clotting mechanism.
There are 2 types of blood thinners: anticoagulants and antiplatelets (WebMD, 2020).
Anticoagulants keep your blood from clotting. Examples of anticoagulants are:
- Apixaban (Eliquis)
- Rivaroxaban (Xarelto)
- Dabigatran (Pradaxa)
- Heparin (Fragmin, Innohep, Lovenox)
- Warfarin (Coumadin, Jantoven)
Antiplatelets target tiny particles in the blood called platelets. Examples of antiplatelets are:
- Ticagrelor (Brilinta)
- Clopidogrel (Plavix)
- Dipyridamole (Persantine)
- Prasugrel (Effient)
Why do people take blood thinners?
Around 2 to 3 million people take blood thinners every year. Some people need to take blood thinners only for a few months, while others may need them permanently.
Blood thinners help with many conditions where blood clots are a risk. Here are examples of conditions that may require a person to take a blood thinner (WebMD, 2020):
- After a heart attack. According to the CDC (Centers for Disease Control and Prevention), heart attack is the number 1 cause of death in the US, with around 805,000 heart attacks occurring each year. That’s equivalent to someone having a heart attack every 40 seconds.
- After a stroke. The CDC also said that stroke is a leading cause of permanent disability. Each year, there are over 795,000 strokes in the US. 87% of these strokes are because of clots.
- After a stent, bypass, and other recent surgical procedures. For instance, over 2 million people get a stent in the US each year (Medtronic, 2019).
- To decrease stroke risk with atrial fibrillation. According to the CDC, atrial fibrillation is the most common type of treated heart arrhythmia.
- Some inflammatory diseases, such as lupus;
- Some obesity problems;
- Artificial heart valves.
Can you take vitamin K while on blood thinners?
As mentioned earlier, warfarin and other VKA blood thinners are affected by vitamin K.
So if you’re taking warfarin or any VKA blood thinner, talk to your doctor first before taking dietary or supplementary vitamin K.
How about other blood thinners?
Outside VKAs, the other types of blood thinners (like Plavix, Brilinta, Eliquis, heparin, or aspirin) are not affected by vitamin K (Earl, 2020).
However, this information about the connections between vitamin K, blood clotting, and blood thinners usually refers to vitamin K1 (phylloquinone), which is just one type of vitamin K.
Does vitamin K2 interfere with blood thinners?
Debates still linger on whether vitamin K2 acts like vitamin K1 when it comes to blood clotting and blood thinners.
We can base the argument that vitamin K2 should not be a problem of blood thinner users primarily on the following premises:
- Vitamin K1 differs from vitamin K2 to some degrees in terms of chemical structures. The dietary sources of vitamin K2 are not the same as that of K1.
- If we assume that all types of vitamin K do have an interfering effect, we know that vitamin K only affects one class of blood thinners—the VKAs.
- Moreover, most blood thinners are not in the VKA class.
While the above premises sound logical, they still don’t prove that vitamin K2 won’t affect blood thinners at all. In fact, there are some pieces of evidence that vitamin K2 could affect VKA blood thinners (e.g., warfarin).
Does vitamin K2 affect blood clotting?
At least 2 articles describe the interaction of vitamin K2 and blood clotting.
One study is done on rats (Hara, 1999).
The other one is a study of vitamin K2’s impact on clotting time (Theuwissen, 2013) where the authors:
- Reported a clinical trial. It wasn’t randomized, but it also wasn’t a re-interpretation of other studies, editorials, or expert opinions.
- Acknowledged the increasing nutraceutical use of vitamin K2 in an environment where many people have both risk factors—taking blood thinners AND arterial plaque with calcification.
- Listed the one blood thinner they used (acenocoumarol).
- Generalized the VKA class. However, they didn’t conflate the VKAs with other blood thinners, like antiplatelets or NOACs (novel oral anticoagulants). That’s important because these medications have different actions. As I mentioned before, supplements impacting the VKAs don’t impact other types of blood thinners.
- Provided an excellent scientific literature review of the scientific evidence on vitamin K2 and VKA.
Why is there little information about vitamin K2 and its interactions?
The recognition of vitamin K2 is still very low. This starts with the US federal guidelines.
- The US minimum daily requirements for vitamin K don’t even mention vitamin K2 (NIH ODS, 2020). This government document admitted the lack of focus on K2. “Several food sources of vitamin K are listed… All values… are for phylloquinone content, except when otherwise indicated, because food composition data for menaquinones are limited.” When you look at the food sources, the typical sources for vitamin K2 (like cheeses and natto) are not listed.
- The Institute of Medicine (US) Panel on Micronutrients doesn’t mention any recommendations for vitamin K2. In fact, they say that vitamin K2 “are not widely distributed in commonly consumed foods” and “only small amounts are found in animal products” (Institute of Medicine (US) Panel on Micronutrients, 2001).
- Furthermore, their key statement about the significance of menaquinones is that they are “produced in substantial amounts by intestinal microorganisms,” and “can also serve as active forms of vitamin K” (Institute of Medicine (US) Panel on Micronutrients, 2001).
There is a lot of research this year in the area of understanding vitamin K2. We will keep you posted as we learn more.
My name is Ford Brewer. I’m a co-founder of PrevMed. We do heart attack, stroke, cancer & disability prevention. I’m licensed in over 40 states. We travel to states to see patients, and we provide telemedicine. Here at PrevMed, we can’t make you do high-Intensity intervals and resistance training or manage an appropriate BMI. But we can help you by telling you what you need to do, why, and how to organize around it, and provide recommendations to support you in staying healthy. If you’re interested in how we can help you, check out our services page.
Centers for Disease Control and Prevention (CDC). Atrial Fibrillation. CDC website. https://www.cdc.gov/heartdisease/atrial_fibrillation.htm. Page last reviewed September 8, 2020. Accessed September 30, 2020.
Centers for Disease Control and Prevention (CDC). Heart Disease Facts. CDC website. https://www.cdc.gov/heartdisease/facts.htm. Page last reviewed September 8, 2020. Accessed September 30, 2020.
Centers for Disease Control and Prevention (CDC). Stroke Facts. CDC website. https://www.cdc.gov/stroke/facts.htm. Page last reviewed September 8, 2020. Accessed September 30, 2020.
Earl L. Vitamin K and Coumadin – What You Need to Know. National Blood Clot Alliance Stop the Clot website. https://www.stoptheclot.org/news/vitamin-k-and-coumadin-what-you-need-to-know. November 24, 2008. Accessed September 30, 2020.
Hara K, Akiyama Y, Tomiuga T, Kobayashi M, Kawashima H. [Interaction of warfarin and vitamin K2 on arterial thrombotic tendency using a rat aorta loop model]. Nihon Yakurigaku Zasshi. 1999 Mar;113(3):185-92. Japanese. doi: 10.1254/fpj.113.185. PMID: 10347843.
InnovixLabs. Vitamin K2 and Coagulation. InnovixLabs website. https://innovixlabs.com/blogs/insights/vitamin-k2-and-coagulation. Published May 6, 2019. Accessed September 30, 2020.
Medtronic. What is Balloon Angioplasty and Stenting? Coronary Artery Disease (CAD). Medtronic website. https://www.medtronic.com/us-en/patients/treatments-therapies/heart-surgery-cad/balloon-angioplasty-stenting-what-is-it.html. Last updated June 2019. Accessed September 30, 2020.
National Institutes of Health (NIH) Office of Dietary Supplements (ODS). Vitamin K: Fact Sheet for Health Professionals. NIH ODS website. https://ods.od.nih.gov/factsheets/vitaminK-HealthProfessional. Updated June 3, 2020. Accessed September 30, 2020.
PrevMed. Vitamin K2 & Cardiovascular Health – What’s the Real Score? PrevMed website. https://prevmedhealth.com/vitamin-k2-cardiovascular-health-whats-the-real-score. Accessed September 30, 2020.
PrevMed. What is Vitamin K2? Can It Remove Arterial Plaque? PrevMed website. https://prevmedhealth.com/vitamin-k2-can-it-remove-plaque. Accessed September 30, 2020.
Theuwissen E, Teunissen KJ, Spronk HMH, et al. Effect of low‐dose supplements of menaquinone‐7 (vitamin K2) on the stability of oral anticoagulant treatment: dose–response relationship in healthy volunteers. J Thromb Haemost. 2013;11:1085-92. doi: 10.1111/jth.12203.
Turck D, Bresson JL, Burlingame B, et al. Dietary reference values for vitamin K. EFSA Journal. 2017;15(5). doi:10.2903/j.efsa.2017.4780
WebMD. Blood Thinner Basics. WebMD website. https://www.webmd.com/dvt/dvt-treatment-tips-for-taking-heparin-and-warfarin-safely. Accessed September 30, 2020.