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Dietary supplement

Vitamin K Ingredients & Drug Interactions

by Thorne

Vitamin K label
See full label image
Capsule Category: Vitamin
Most serious interaction: Major
Clinical methodology reviewed by · Updated Sep 9, 2026 · Label data from the NIH DSLD
What is this page for?

First and foremost: checking Vitamin K against your medications. The heart of this page is the interaction checker and the full interaction report — how this product’s ingredients may interact with prescription and over-the-counter medicines you may be taking.

Around that, we add a pharmacist’s high-level view of the product as a whole — what’s inside, the evidence for its stated use, how transparent the label is, and what safety data exists — so you can see the full picture in one place. It’s educational information from our licensed clinical databases and the clinical staff at HelloPharmacist — not medical advice — and we don’t sell or endorse products. Our editorial policy

The interaction bottom line Most serious interaction: Major

Vitamin K is a dietary supplement by Thorne with 1 active ingredient. Its ingredients are commonly taken for supporting normal blood clotting, bone health, heart and vascular health.Based on those ingredients, 2 medications have a known interaction with it, the most serious rated major. The ingredients most likely to interact are Vitamin K. Use the checker below to test your specific medication, or read the full HelloPharmacist Interaction Report.

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Check Your Meds Against Vitamin K by Thorne

Ask about any prescription or over-the-counter medication and we check it for interactions with Vitamin K by Thorne — and tell you which ingredient is responsible.

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HelloPharmacist Scorecard of Vitamin K by Thorne

Our pharmacy team’s full take, with four database checks built into the cards below — a summary of what is known, not a grade of the product itself.

From our pharmacy team — supplement deep dive

Generated from HelloPharmacist’s pharmacist-curated databases and editorial rules · Last generated Jul 11, 2026

What’s inside

Full disclosure
Ingredient Transparency · database check
Full

Every active ingredient lists its own amount on the label.

Why this rating?
  • The label discloses an exact amount for 2 of its 2 active ingredients.
  • “Vitamin K” is listed as a grouped ingredient — the label gives one combined amount (6,090 mcg) without saying how much of each component you get.
  • “Vitamin K2” is listed as a grouped ingredient — the label doesn't break down how much of each component you get.

This product contains 2 active ingredients: Vitamin K1 and Menaquinone-4 (a form of Vitamin K2). Both are forms of vitamin K, a fat-soluble nutrient that plays a role in blood clotting and bone health.

The capsule also contains a few inactive ingredients—microcrystalline cellulose (a filler), hypromellose and silicon dioxide (for capsule structure), and vitamin E.

Does it work?

Strong evidence
Evidence for Intended Use · database check
By FDA rules, dietary supplements can’t claim to treat, cure, or prevent disease — so labels speak in careful marketing language. We discern each product’s intended use from its name, label claims, and label statements, then grade the clinical evidence for that use. How these ratings are computed
Strong

Clinical evidence supports at least one of this product's ingredients for its stated purpose.

Why this rating?
  • The label markets this product for: Bone support and heart/vessel health.
  • We looked for evidence on: Cardiovascular disease (CVD), Hemorrhagic disease, Hypoprothrombinemia, Osteoporosis, Vitamin K-dependent clotting factors deficiency (VKCFD), Warfarin anticoagulation — and 2 related terms.
  • The strongest evidence on file: Vitamin K is rated "Effective" for Hemorrhagic disease (Natural Medicines).
  • Also on file: Vitamin K is rated "Effective" for Hypoprothrombinemia, Warfarin anticoagulation, Vitamin K-dependent clotting factors deficiency (VKCFD).
  • Also on file: Vitamin K is rated "Possibly Effective" for Osteoporosis.

Vitamin K is effective for treating vitamin K deficiency and related clotting disorders—including hypoprothrombinemia (low levels of clotting factors) and hemorrhagic disease. It's also rated effective for managing warfarin anticoagulation when vitamin K levels are low.

For osteoporosis, the evidence is less certain; vitamin K is rated possibly effective, meaning the science is still developing in this area.

The evidence, ingredient by ingredient Vitamin K

How safe is it?

Well-documented data
Safety Information · database check
Well characterized

Adverse-effect, pregnancy, and general safety data are on file for most of these ingredients.

Why this rating?
  • We hold adverse-effect (side-effect) data for 1 of the 1 matched ingredient.
  • Pregnancy & breastfeeding safety ratings cover 1 of 1.
  • General safety write-ups exist for 1 of 1.
  • Remember: this measures how much safety information exists. Thin data is not the same as being safe.

Taken by mouth, vitamin K is generally well tolerated in healthy people at the amounts found in food and typical supplements. The most common mild side effects are nausea, diarrhea, stomach upset, and abdominal pain.

Serious adverse effects are rare; they have been reported mainly with intravenous dosing in special populations like premature infants. The data shows vitamin K is likely safe in pregnancy and while breastfeeding.

That said, if you're taking supplements (rather than just eating vitamin K-rich foods), check with your doctor first, especially if you have any medical conditions.

Side effects, ingredient by ingredient Vitamin K

Meds to double-check

Major interaction found
Known Interaction Concern · database check
Major identified

At least one ingredient has a documented Major-severity interaction. Check your medications for a personalized result.

Why this rating?
  • 1 of the 1 matched ingredient can interact with medications — Vitamin K.
  • The most serious interaction on file is rated Major.
  • Some involve high-stakes drug classes: anticoagulant / antiplatelet drugs.
  • For scale: 2 individual medications appear in the full list. A big number alone doesn't make a product dangerous — what matters is whether YOUR medication is on it, so run yours through the interaction checker on this page.

If you take warfarin (Coumadin), a blood thinner, double-check with your pharmacist or doctor before using this product. Vitamin K can reduce warfarin's effectiveness and increase your clot risk.

This is a Major interaction.

Check your own medication Run your meds through the checker above

The bottom line

Scorecard at a glanceFully disclosed formula with clinical evidence supporting its stated purpose. Major medication interactions have been identified, and safety information is well characterized.

Vitamin K is useful if you have a documented vitamin K deficiency or a clotting disorder, or if your doctor prescribes it. If you take warfarin, do not start this supplement without medical guidance—your anticoagulation could be compromised.

Talk to your pharmacist or doctor before adding it, particularly if you're on any medications.

Educational only — not medical advice; always confirm with your pharmacist. Our editorial policy · How we use AI

Assessment coverage: 2 of 2 active ingredients matched to our full ingredient reviews (monographs). Based on the product label dated May 21, 2025.

This Scorecard evaluates available label information, ingredient evidence, and known medication-safety considerations. It does not independently verify product identity, purity, potency, contamination, or manufacturing quality. How these ratings are computed

At a glance

General information

Key facts about Vitamin K, straight from the product label.

Brand Thorne
Barcode (UPC) 693749006619
Net contents 60 Capsule(s)
Market status On market
Date entered into DSLD May 21, 2025
DSLD ID 328817
Product type Vitamin
Supplement form Capsule
Dietary claims / uses Nutrient, All Other, Structure/Function
Intended target group(s) Adult (18 - 50 Years), Gluten Free
From the label
Everything in this section is reproduced from the manufacturer’s own product label — it’s the label speaking, not HelloPharmacist. We show it so you can see exactly what the maker states; we don’t verify or endorse those statements.

Supplement Facts

The label details for Vitamin K by Thorne, sourced from the NIH Dietary Supplement Label Database.

Supplement Facts

Daily Value (DV) Target Group(s):
Adults and children 4 or more years of age
Minimum serving Sizes:
1 Capsule(s)
Maximum serving Sizes:
1 Capsule(s)
Servings per container
60
UPC/BARCODE
693749006619
IngredientAmount% DV
Vitamin K6090 mcg5075%
Vitamin K20 NP--
Vitamin K11 mg--
Menaquinone-45 mg--

Other ingredients: Microcrystalline Cellulose, Hypromellose, Silicon Dioxide, Vitamin E

Tap any ingredient to jump to its full detail below.

Label statements
These statements are the manufacturer’s wording, reproduced from the product label — the label is saying it, not HelloPharmacist. We don’t verify or endorse them.
Formulation

Bone support Foundational Heart/Vessels

Gluten free

Suggested/Recommended/Usage/Directions

Suggested use: Take 1 capsule one to two times daily or as recommended by your health-care practitioner.

Precautions

Tamper evident: Use only if bottle is sealed.

If pregnant, consult your health-care practitioner before using this product.

As vitamin K interferes with the effect of anti-coagulant drugs (like Coumadin), the concurrent use of these agents should be avoided.

Storage

Store tightly sealed in a cool, dry place.

Seals/Symbols

Manufactured in the USA using US & imported ingredients NSF Contents Certified

Formula

Vitamin K K1 and two forms of K2

FDA Statement of Identity

Dietary Supplement

FDA Disclaimer Statement

This statement has not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease.

Is this label outdated? Report a formula or label change and our pharmacy team will review it.

See for yourself

Vitamin K by Thorne label

The label scan from the NIH Dietary Supplement Label Database. Tap to enlarge.

Vitamin K label

Label images are published by the NIH Dietary Supplement Label Database for the version of this product on file. Always read your actual product label.

View the full label (PDF)
What’s inside

The Ingredients in Vitamin K by Thorne

This is the 1 active ingredient this product is made of. Select it to open its full monograph.

Serving size1 Capsule(s) Dosage formCapsule Servings per container60 Amounts shown are per serving.

Vitamin K

Interacts with
2 drugs
6090 mcg per serving

Vitamin K is an essential nutrient your body needs for normal blood clotting and to support healthy bones. Most people get enough from food, but suppl...

Vitamin K monograph & interactions

Other (inactive) ingredients: Microcrystalline Cellulose, Hypromellose, Silicon Dioxide, Vitamin E. These complete the product’s ingredient list but are not active constituents.

Interaction report

Vitamin K by Thorne Drug Interactions

Want to check YOUR meds against Vitamin K?

Ask about interactions with your drugs in plain English — “Can I take it with lisinopril?” — and we find you the answer in seconds, ingredient by ingredient.

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2Drugs
2 Major

Ingredients driving the most interactions

Vitamin K 2

Individual Drug Interactions

The ingredients in Vitamin K interact with 2 drugs. Click any drug to see the details.

1 of the 1 ingredient in Vitamin K interact with drugs. Each result below shows which ingredient is responsible. Vitamin K

Each ingredient & the kinds of drugs it affects

For each ingredient in Vitamin K with known interactions, here are the types of medications it can affect. Open any type for the detail — or search your exact drug in the checker above.

Vitamin K1 drug type · 2 drugs

Warfarin (Coumadin)

Vitamin K can antagonize and reverse the therapeutic effects of warfarin.
Vitamin K antagonizes the effects of warfarin. Excessive vitamin K intake, either from supplements or from changes in the diet, can reduce the anticoagulant effect of warfarin.

Likelihood Likely Evidence C
Vitamin K full monograph & interactions
The maker

Brand information

Manufacturer and brand details for Vitamin K, from the product label.

Thorne

See all Thorne products
Name
Thorne Research, Inc.
Phone Number
1-800-228-1966
Pharmacist Counseling Corner

Vitamin K by Thorne: Common Questions

Does Vitamin K by Thorne interact with any medications?
Yes. Based on its ingredients, Vitamin K has a known interaction with 2 medications, including 2 rated major. Use the checker to see how it interacts with a specific drug.
How can one product interact with so many drugs?
Vitamin K contains a single active ingredient, and that one ingredient can interact with many different medications on its own. We check it against each medication and show the mechanism responsible.
Where does this information come from?
The product label data comes from the NIH Dietary Supplement Label Database (DSLD); the interaction data is built on the Natural Medicines database and reviewed by HelloPharmacist pharmacists.
Can I take Vitamin K if I'm on warfarin?
No—not without talking to your doctor first. Vitamin K can antagonize warfarin and make it less effective at preventing clots. Your doctor may adjust your warfarin dose or advise against the supplement depending on your situation.
What are the main side effects of vitamin K supplements?
The most common ones taken by mouth are nausea, diarrhea, stomach upset, and abdominal pain. These are usually mild. Serious side effects are rare.
Is vitamin K safe during pregnancy and breastfeeding?
Yes. Vitamin K is rated likely safe in pregnancy and lactation. Still, if you're pregnant or nursing and considering a supplement, run it past your doctor or pharmacist to be sure it fits your situation.
Does vitamin K help with osteoporosis?
The evidence is still developing. Vitamin K is rated possibly effective for osteoporosis, meaning it may help but the science isn't conclusive yet. Talk to your doctor about whether it's right for you.
What's the difference between Vitamin K1 and the K2 (Menaquinone-4) in this product?
Both are forms of vitamin K, which your body needs for clotting and bone health. Vitamin K1 is the form found mainly in leafy greens; Menaquinone-4 is a type of K2 found in some animal foods and produced in your gut. This product contains both.

Written and reviewed by the HelloPharmacist editorial staff. Our editorial policy

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Label information is sourced from the NIH Dietary Supplement Label Database and reflects the product version on file; always read your actual product label. This page is for education only and is not a substitute for professional medical advice. Confirm with your pharmacist or doctor before combining supplements and medications.

Vitamin K label
Go deeper

The Full Monographs Behind Vitamin K’s Ingredients

Every ingredient we hold a full HelloPharmacist monograph for — uses, evidence, safety, and the complete interaction list.

Herb & supplement monograph

Vitamin K

Interacts with 2 drugs

Vitamin K is an essential nutrient your body needs for normal blood clotting and to support healthy bones. Most people get enough from food, but supplements are sometimes used for deficiency...

Read the full Vitamin K monograph →
Sources

Sources & How We Checked

Vitamin K's label data comes from the NIH Dietary Supplement Label Database; the ingredient interaction data is from the Natural Medicines database, reviewed by our pharmacists.

Content is written and reviewed by licensed HelloPharmacist pharmacists. See our data sources and editorial standards for how this information is built and checked.

The 11 references behind this product’s interaction data

Every citation that drives the interaction findings for this product’s ingredients, from the evidence-graded Natural Medicines (TRC Healthcare) database. Open an ingredient to browse its citations — links open the study on PubMed or the publisher’s site.

Vitamin K 11 references
  1. McEvoy GK, ed. AHFS Drug Information. Bethesda, MD: American Society of Health-System Pharmacists, 1998.
  2. Food and Nutrition Board, Institute of Medicine. Dietary Reference Intakes for Vitamin A, Vitamin K, Arsenic, Boron, Chromium, Copper, Iodine, Iron, Manganese, Molybdenum, Nickel, Silicon, Vanadium, and Zinc. Washington, DC: National Academy Press, 2002.
  3. Crowther MA, Ageno W, Garcia D, et al. Oral vitamin K versus placebo to correct excessive anticoagulation in patients receiving warfarin: a randomized trial. Ann Intern Med. 2009;150(5):293-300. PubMed
  4. Dietary vitamin K guidance: an effective strategy for stable control of oral anticoagulation? Nutr Rev. 2010;68(3):178-81. PubMed
  5. Kim JS, Nafziger AN, Gaedigk A, et al. Effects of oral vitamin K on S- and R-warfarin pharmacokinetics and pharmacodynamics: enhanced safety of warfarin as a CYP2C9 probe. J Clin Pharmacol. 2001 Jul;41(7):715-22. PubMed
  6. Riegert-Johnson, D. L. and Volcheck, G. W. The incidence of anaphylaxis following intravenous phytonadione (vitamin K1): a 5-year retrospective review. Ann.Allergy Asthma Immunol. 2002;89(4):400-406. PubMed
  7. Dezee, K. J., Shimeall, W. T., Douglas, K. M., Shumway, N. M., and O'malley, P. G. Treatment of excessive anticoagulation with phytonadione (vitamin K): a meta-analysis. Arch.Intern.Med. 2-27-2006;166(4):391-397. DOI
  8. Dentali, F., Ageno, W., and Crowther, M. Treatment of coumarin-associated coagulopathy: a systematic review and proposed treatment algorithms. J.Thromb.Haemost. 2006;4(9):1853-1863. PubMed
  9. Caluwé R, Vandecasteele S, Van Vlem B, Vermeer C, De Vriese AS. Vitamin K2 supplementation in haemodialysis patients: a randomized dose-finding study. Nephrol Dial Transplant. 2014;29(7):1385-90.
  10. Huang ZB, Wan SL, Lu YJ, Ning L, Liu C, Fan SW. Does vitamin K2 play a role in the prevention and treatment of osteoporosis for postmenopausal women: a meta-analysis of randomized controlled trials. Osteoporos Int. 2015;26(3):1175-86. PubMed
  11. Hunnali CR, Devi U, Kitchanan S, Sethuraman G. Three Different Regimens for Vitamin K Birth Prophylaxis in Infants Born Preterm: A Randomized Clinical Trial. J Pediatr 2023;255:98-104. PubMed

See these in context on the Vitamin K monograph →

Parts of this content are provided by the Therapeutic Research Center, LLC.

DISCLAIMER: Currently this does not check for drug-drug interactions. This is not an all-inclusive comprehensive list of potential interactions and is for informational purposes only. Not all interactions are known or well-reported in the scientific literature, and new interactions are continually being reported. Input is needed from a qualified healthcare provider including a pharmacist before starting any therapy. Application of clinical judgment is necessary.

© 2021 Therapeutic Research Center, LLC

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