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Dietary supplement

Vitamin K 100 Ingredients & Drug Interactions

by GNC

Vitamin K 100 label
See full label image
Tablet Or Pill Category: Vitamin
Most serious interaction: Major
Clinical methodology reviewed by · Updated Sep 30, 2026 · Label data from the NIH DSLD
What is this page for?

First and foremost: checking Vitamin K 100 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 100 is a dietary supplement by GNC 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 100 by GNC

Ask about any prescription or over-the-counter medication and we check it for interactions with Vitamin K 100 by GNC — and tell you which ingredient is responsible.

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HelloPharmacist Scorecard of Vitamin K 100 by GNC

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 Sep 24, 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 1 of its 1 active ingredient.
  • No proprietary blends here — you can verify the dose of every single component.

Vitamin K 100 by GNC contains a single active ingredient: vitamin K. This product delivers 100 units of vitamin K per dose — a form the body uses to support blood clotting and bone health.

The tablet also contains two inactive ingredients (dicalcium phosphate and cellulose) as binders and fillers.

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: support normal blood clotting and bone health.
  • We looked for evidence on: Hemorrhagic disease, Hypoprothrombinemia, Intraventricular hemorrhage, Vitamin K-dependent clotting factors deficiency (VKCFD), Warfarin anticoagulation, Osteoporosis — and 3 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.

The evidence supports vitamin K for correcting vitamin K deficiency and related bleeding disorders. It's effective for low prothrombin levels (a measure of clotting ability) and for vitamin K-dependent clotting factor deficiency (VKCFD).

It's also effective for managing warfarin-related bleeding when a doctor prescribes it for that purpose. For osteoporosis, the evidence is possibly effective — meaning there's some research backing its use, but the data isn't conclusive enough yet to call it proven.

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 amounts found in food and supplements for healthy people. The most common side effects are mild: nausea, stomach upset, and diarrhea — a small number of people report these.

There's no established safety concern with intravenous vitamin K in normal clinical doses, though extremely rare cases of allergic-type reactions have been reported with that route. Vitamin K is likely safe during pregnancy and lactation, so the safety data don't advise against use if you're pregnant or nursing.

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) or any blood thinner (anticoagulant), check with your doctor before adding this product — vitamin K can weaken its effect and put you at risk for clots. The medication checker below covers the interactions we have on file; use it to scan your exact drugs.

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 100 is straightforward if you're trying to correct a deficiency or support bone health — and it's generally well tolerated. The big exception: if you take warfarin (Coumadin) or any other blood thinner, do not take this supplement without checking with your doctor first, because vitamin K can reduce how well your anticoagulant works.

Talk it over with your own doctor or pharmacist before starting, especially 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: 1 of 1 active ingredient matched to our full ingredient reviews (monographs). Based on the product label dated Oct 26, 2011.

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 100, straight from the product label.

Brand GNC
Barcode (UPC) 048107173852
Net contents 100 Vegetarian Tablet(s)
Market status On market
Date entered into DSLD Oct 26, 2011
DSLD ID 1416
Product type Vitamin
Supplement form Tablet Or Pill
Dietary claims / uses All Other, Structure/Function
Intended target group(s) Adult (18 - 50 Years)
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 100 by GNC, 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 Tablet(s)
Maximum serving Sizes:
1 Tablet(s)
UPC/BARCODE
048107173852
IngredientAmount% DV
Vitamin K100 mcg125%

Other ingredients: Dicalcium Phosphate, Cellulose

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.
FDA Disclaimer Statement

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.

FDA Statement of Identity

DIETARY SUPPLEMENT

Formula

Ko

Precautions

KEEP OUT OF REACH OF CHILDREN.

Storage

Store in a cool, dry place.

General Statements

100 mcg

ACTUAL SIZE

For more information:

helps the body transport calcium

Lot No./Best By:

Potency verified by GNC procedure #5024. Conforms to USP <2091> for weight. Meets USP <2040> disintegration.

SHOP NOW

General

CODE 99011 KKG

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

See for yourself

Vitamin K 100 by GNC label

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

Vitamin K 100 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 100 by GNC

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

Serving size1 Tablet(s) Dosage formTablet Or Pill Amounts shown are per serving.

Vitamin K

Interacts with
2 drugs
100 mcg per serving Form: Phytonadione

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: Dicalcium Phosphate, Cellulose. These complete the product’s ingredient list but are not active constituents.

Interaction report

Vitamin K 100 by GNC Drug Interactions

Want to check YOUR meds against Vitamin K 100?

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.

 Go to the checker
2Drugs
2 Major

Ingredients driving the most interactions

Vitamin K 2

Individual Drug Interactions

The ingredients in Vitamin K 100 interact with 2 drugs. Click any drug to see the details.

1 of the 1 ingredient in Vitamin K 100 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 100 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 100, from the product label.

GNC

See all GNC products
Name
General Nutrition Corporation
City
Pittsburgh
State
PA
ZipCode
15222
Phone Number
1-888-462-2548
Web Address
gnc.com
Pharmacist Counseling Corner

Vitamin K 100 by GNC: Common Questions

Does Vitamin K 100 by GNC interact with any medications?
Yes. Based on its ingredients, Vitamin K 100 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 100 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.
Will vitamin K hurt warfarin?
Yes — it's a major concern. Vitamin K reverses warfarin's effect, which means your blood won't clot normally if you're taking both. If you're on warfarin, do not take this supplement without your doctor's say-so. They may adjust your warfarin dose or check you more often.
What side effects does vitamin K have?
Taken by mouth, it's generally well tolerated. Some people report mild nausea, stomach upset, or diarrhea — that's the short list. Serious side effects from the oral form are very rare.
Is it safe to take vitamin K while pregnant?
Yes, vitamin K is likely safe during pregnancy. The safety data support its use, so there's no reason to avoid it if you're pregnant. As always, talk with your doctor about what's right for your situation.
Can I take this if I'm breastfeeding?
Yes — vitamin K is likely safe during breastfeeding. No safety concerns are flagged for nursing mothers in the data we hold.
Does vitamin K actually work for osteoporosis?
The evidence is possibly effective, which means there's some research behind it but it's not proven yet. If bone health is your goal, ask your doctor whether this makes sense for you alongside other treatments.
What does this vitamin actually do in your body?
Vitamin K is essential for blood clotting — your body uses it to make the proteins that stop bleeding. It also plays a role in bone health. This supplement is used to treat vitamin K deficiency and related clotting problems.

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 100 label
Go deeper

The Full Monographs Behind Vitamin K 100’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 100'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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