This is the most important safety topic for vitamin K2. If you take warfarin (Coumadin) or a similar blood thinner, vitamin K can change how your medication works. Here's what you need to know.
Written by Vita Globe Editorial Team | Reviewed against NIH and MedlinePlus guidance and peer-reviewed research
Can you take vitamin K2 if you're on a blood thinner?
If you take warfarin, don't take vitamin K2 unless your doctor says so. Warfarin works by interfering with vitamin K, so changing your vitamin K intake can make it less effective[1][2]. People on warfarin are advised to keep vitamin K intake consistent and to talk with their provider before taking any vitamins or supplements[3]. MK-7 is especially relevant because it counteracted an oral anticoagulant at lower doses than K1[4].
Caveat: Newer blood thinners work differently from warfarin, but you should still check any supplement with your prescriber.
Sources: NIH ODS · Holbrook et al., 2005 · MedlinePlus · Schurgers et al., 2007 · Verified 2026-09-27
In this article
How does warfarin interact with vitamin K?
Your liver uses vitamin K to activate clotting factors. Warfarin is a vitamin K antagonist: it interferes with that process, so your blood takes longer to clot[1].
Because of this, how much vitamin K you get can shift warfarin's effect. More vitamin K can make warfarin less effective. A systematic review of warfarin interactions identified vitamin K-rich foods and supplements among the factors that can alter its effect[2].
Your doctor tracks this with a blood test called the INR (or PT). It helps make sure you're on the right warfarin dose[3].
Why is vitamin K2 especially important for warfarin users?
MK-7, a form of K2 used in many supplements, stays in the bloodstream much longer than K1. In a study of volunteers on an oral anticoagulant, MK-7 counteracted the drug at lower doses than K1, and the researchers cautioned that MK-7 supplements could interfere with anticoagulant treatment[4].
In healthy people not taking blood thinners, low-dose MK-7 didn't change a laboratory measure of clotting[5]. The concern is specifically about people whose clotting is being carefully managed with a vitamin K antagonist.
Do you have to avoid vitamin K completely?
No, and that's a common misunderstanding. Current guidance focuses on consistency, not avoidance. MedlinePlus advises people on warfarin not to change the amount of vitamin K-rich foods they eat from day to day or week to week[3]. The NIH also emphasizes keeping vitamin K intake consistent[1].
The same logic applies to supplements. Starting, stopping or changing a K2 supplement is a change in vitamin K intake, which is why it needs to be coordinated with your doctor.
The honest summary
- Vitamin K counteracts warfarin.
- MK-7 can affect anticoagulation at relatively low doses.
- Consistency is the goal, not total avoidance.
- Never start, stop or change K2 on warfarin without your doctor.
What about other blood thinners?
Newer oral anticoagulants and antiplatelet drugs (like aspirin or clopidogrel) don't work by blocking vitamin K the way warfarin does. Even so, don't assume any supplement is fine. Some supplements affect bleeding risk in other ways, and your prescriber knows your full picture. MedlinePlus advises talking with your provider before taking any over-the-counter medicines, vitamins or supplements while on warfarin[3].
How to talk to your doctor about K2
- Bring the product (or a photo of the Supplement Facts panel) to your appointment.
- Ask whether K2 fits your treatment plan, and if so, what dose.
- If you start, take it at a consistent dose every day and ask whether you need extra INR checks[3].
- Tell every provider, including your pharmacist and dentist, about all your supplements.
For general safety info, see vitamin K2 side effects.
Our option
Vita Globe Vitamin K2 Gummies
Our Vitamin K2 Gummies contain vitamin K, so they're not for anyone on warfarin unless their doctor approves. They're raspberry-flavored, with a suggested use of 2 gummies once daily, and they're vegan-friendly, gluten-free and non-GMO, made without artificial colors or flavors. Like every Vita Globe product, they're tested by an independent third-party lab.
Frequently asked questions
Can I take vitamin K2 with warfarin?
Only if your doctor approves and monitors you. Vitamin K reduces warfarin's effect[1][2], and MK-7 can do this at relatively low doses[4].
Does vitamin K2 thin your blood?
No. Vitamin K is needed for normal clotting[1]. In healthy people, low-dose MK-7 didn't change a clotting measure[5].
Can I take K2 with Eliquis or Xarelto?
These drugs don't work through vitamin K the way warfarin does, but always check with your prescriber or pharmacist before adding any supplement.
Should I stop eating leafy greens on warfarin?
No. The advice is to keep your intake consistent rather than cutting these foods out[3].
Sources
- Office of Dietary Supplements, National Institutes of Health. Vitamin K: Fact Sheet for Health Professionals. Updated March 29, 2021. ods.od.nih.gov
- Holbrook AM, Pereira JA, Labiris R, et al. Systematic overview of warfarin and its drug and food interactions. Arch Intern Med. 2005;165(10):1095-1106. doi:10.1001/archinte.165.10.1095
- MedlinePlus Medical Encyclopedia. Taking warfarin. U.S. National Library of Medicine. Reviewed January 1, 2025. medlineplus.gov
- Schurgers LJ, Teunissen KJF, Hamulyák K, Knapen MHJ, Vik H, Vermeer C. Vitamin K-containing dietary supplements: comparison of synthetic vitamin K1 and natto-derived menaquinone-7. Blood. 2007;109(8):3279-3283. doi:10.1182/blood-2006-08-040709
- Theuwissen E, Cranenburg EC, Knapen MH, et al. Low-dose menaquinone-7 supplementation improved extra-hepatic vitamin K status, but had no effect on thrombin generation in healthy subjects. Br J Nutr. 2012;108(9):1652-1657. doi:10.1017/S0007114511007185
About the Vita Globe Editorial Team
The Vita Globe Editorial Team researches and writes our wellness content, working from peer-reviewed research, systematic reviews and guidance from bodies such as the NIH and the FDA. We cite our sources inline and update articles when the evidence changes.
These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease. This article is for informational purposes only and is not a substitute for medical advice. Talk to your healthcare provider before starting any new supplement, particularly if you are pregnant, nursing, taking medication, or caring for a child.
