Drug & supplement interaction

Vitamin K + Tamoxifen Citrate

Tamoxifen Citrate brand names: Nolvadex, Soltamox.

No Known Interaction
Medically reviewed by · Updated July 2026 · Pair last verified Sep 27, 2026
The bottom line No known interaction

We found no known interaction between Vitamin K and Tamoxifen Citrate in our sources. Absence of a documented interaction is not the same as proven safety, and does not guarantee one does not exist. Do not start, stop, or change a medication or supplement based on this page; confirm with your pharmacist or doctor first. Additionally, although there is no interaction, the two are separately associated with some of the same side effects, which would make a new symptom harder to attribute to one or the other.

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Interaction report

Vitamin K and Tamoxifen Citrate

We checked these two against our interaction database. Here is what we found.

No Known Interaction Found

We did not find a documented interaction between Tamoxifen Citrate and Vitamin K in our sources. This does not guarantee that the combination is completely free of risk — there is often limited research on supplements and herbal products, especially around drug interactions.

If you decide to take both, the practical routine is simple: add one new thing at a time and note the date you started it. If the combination is going to disagree with you, it usually shows in the first days to a couple of weeks — and a start date turns “I’ve been feeling off” into something a pharmacist can actually work with. Do not stop a prescribed medicine on your own.

Always talk with your pharmacist or doctor before making changes to your medications or supplements, particularly if you take several medications or have an ongoing health condition.

Vitamin K safety at a glance

Vitamin K overall Generally safe Generally safe in amounts found in food and most supplements for healthy people.
Pregnancy Likely Safe When used orally in amounts that do not exceed the daily adequate intake level (AI). A tolerable upper intake level for vitamin K in pregnancy and lactation has... Read the full pregnancy detail
Breastfeeding Likely Safe When used orally in amounts that do not exceed the daily adequate intake level (AI). A tolerable upper intake level for vitamin K in pregnancy and lactation has... Read the full breastfeeding detail

Pregnancy & breastfeeding ratings are from Natural Medicines (Therapeutic Research Center) — the full detail is in the Special populations card below. Safety guidance is general; always confirm with your pharmacist or doctor for your situation.

Still wondering about combining Tamoxifen Citrate and Vitamin K? Ask Dr. Brian Staiger, PharmD, BCPS directly ›
How we checked

Why No Interaction Is Listed for Tamoxifen Citrate

Interactions in our licensed database are recorded against drug classes, not just single drug names. Tamoxifen Citrate is filed under 9 classifications — including cytochrome p450 2c9 (cyp2c9) substrates, glucuronidated drugs, qt interval-prolonging drugs. Vitamin K has documented interactions with 1 drug class — the most serious being warfarin (coumadin) (major) — and none of Tamoxifen Citrate’s classifications are among them.

Classification data comes from our licensed Natural Medicines dataset. A medication can belong to classes beyond those recorded there, so this describes how the check was run — it is not a safety guarantee.

Keep it in perspective

Vitamin K Does Interact With Other Medications

Vitamin K has 2 major, known drug interactions in our database — Tamoxifen Citrate isn’t one of them. If you take anything else, check it against the full list below.

Major 2 No known interaction 2,828 (incl. Tamoxifen Citrate)
Taking anything else?

Check Another of Your Medications Against Vitamin K

Covers the 2,830 medications we’ve checked against Vitamin K. Pick one to open its full report.

What to actually watch for

No Interaction Found — But Data Suggests Vitamin K and Tamoxifen Citrate May Share Several of the Same Side Effects

This is not an interaction. Neither one changes how your body handles the other, and nothing here says they react together. What our sources do show is that each has separately been linked to the effects below — so taking both can make those effects more likely to turn up, and harder to pin on one or the other if they do. 3 of them are worth acting on rather than waiting out — marked below.

  • Yellowing of the skin or eyes Worth acting on Additional detail

    Vitamin K

    “Orally, vitamin K3 (menadione) has been linked to hepatotoxicity. Vitamin K3 is no longer used therapeutically in North America because it has been linked to hepatic toxicity and jaundice in animal research.”

    Vitamin K · Natural Medicines adverse-effect record, reported in neonatal jaundice.

    1 source cited
    1. 7135. 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.

    Tamoxifen Citrate

    Listed in the ADVERSE REACTIONS section of the FDA label for Tamoxifen Citrate. Read the label on DailyMed ›

  • A severe allergic reaction Worth acting on Additional detail

    Vitamin K

    “Intravenously, vitamin K can cause reactions that resemble hypersensitivity or anaphylaxis. These reactions are rare. It is unclear whether the adverse effect is caused by the drug or a component of the solution. There have been very rare cases of hyperbilirubinemia, particularly in premature neonates, following large doses of vitamin K (15).”

    Vitamin K · Natural Medicines adverse-effect record, reported in myasthenia gravis.

    3 sources cited
    1. 85389. 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
    2. 15. McEvoy GK, ed. AHFS Drug Information. Bethesda, MD: American Society of Health-System Pharmacists, 1998.
    3. 112100. 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

    Tamoxifen Citrate

    Listed in the ADVERSE REACTIONS section of the FDA label for Tamoxifen Citrate. Read the label on DailyMed ›

  • An allergic reaction Worth acting on Additional detail

    Vitamin K

    Recorded for Vitamin K in the same Natural Medicines adverse-effect record shown under A severe allergic reaction above.

    Tamoxifen Citrate

    Listed in the ADVERSE REACTIONS section of the FDA label for Tamoxifen Citrate. Read the label on DailyMed ›

  • Stomach upset Additional detail

    Vitamin K

    Recorded for Vitamin K in the same Natural Medicines adverse-effect record shown under A severe allergic reaction above.

    Tamoxifen Citrate

    Listed in the ADVERSE REACTIONS section of the FDA label for Tamoxifen Citrate. Read the label on DailyMed ›

  • Stomach pain Additional detail

    Vitamin K

    “Orally, vitamin K can cause mild to moderate gastrointestinal side effects. The most common effects include nausea, abdominal pain, and diarrhea.”

    Vitamin K · Natural Medicines adverse-effect record, reported in diarrhea.

    2 sources cited
    1. 91450. 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.
    2. 91451. 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

    Tamoxifen Citrate

    Listed in the ADVERSE REACTIONS section of the FDA label for Tamoxifen Citrate. Read the label on DailyMed ›

  • Diarrhea / Nausea Additional detail

    Vitamin K

    Recorded for Vitamin K in the same Natural Medicines adverse-effect record shown under A severe allergic reaction above.

    Tamoxifen Citrate

    Listed in the ADVERSE REACTIONS section of the FDA label for Tamoxifen Citrate. Read the label on DailyMed ›

Reported for Vitamin K but not commonly for Tamoxifen Citrate: liver problems.

Effects for Tamoxifen Citrate come from the ADVERSE REACTIONS section of its FDA label; effects for Vitamin K come from the Natural Medicines adverse-effect record, quoted above. Wording is matched across sources by our own clinical vocabulary, so treat this as a prompt to pay attention, not a diagnosis.

Special populations

Vitamin K in Pregnancy & Breastfeeding

Pregnancy And Lactation Likely Safe

When used orally in amounts that do not exceed the daily adequate intake level (AI). A tolerable upper intake level for vitamin K in pregnancy and lactation has not been set.

DISCLAIMER: This tool is intended for informational purposes only, and should not be interpreted as specific medical advice. Patients should consult with a qualified healthcare provider before making decisions about therapies and/or health conditions.© 2026 Therapeutic Research Center

Overlapping uses

What Tamoxifen Citrate Is Prescribed For, and What Vitamin K Has Been Studied For

These two come up together because they touch the same health topic — not because they do the same job. Tamoxifen Citrate is a prescription medicine with approved uses on its FDA label. Vitamin K is a supplement: what follows is what researchers have looked at it for, and how strong that evidence is.

Tamoxifen Citrate is prescribed for: Tamoxifen is used to treat metastatic breast cancer (breast cancer that has spread) in both women and men, and as adjuvant (after-surgery) therapy for early-stage breast cancer in women. It also reduces the occurrence of cancer in the opposite breast when used as adjuvant therapy. In women with ductal carcinoma in situ (DCIS) — a very early, non-invasive form of breast cancer — tamoxifen is used after breast surgery and radiation to reduce the risk of developing invasive breast cancer. It is also approved to reduce the incidence of breast cancer in women who are at high risk but have not yet been diagnosed.

Read the rest of what Tamoxifen Citrate is prescribed for

Soltamox (oral solution) is specifically indicated for all of these uses in adult patients.

Vitamin K has been studied for:

  • Breast cancer studied, not established Vitamin K has been studied for this. Natural Medicines rates the evidence: Insufficient Reliable Evidence To Rate Read what the research shows

    Vitamin K for breast cancer

    It is unclear if dietary intake of vitamin K2 reduces the risk of breast cancer.

Effectiveness ratings and the research summaries above are the verbatim record from the Natural Medicines database, which grades evidence from “Effective” down to “Insufficient Reliable Evidence To Rate”. A rating below the top of that scale means researchers have looked at it — not that it works, and never that it can stand in for a prescribed medicine. Do not stop or replace Tamoxifen Citrate on your own; if you are taking Vitamin K for the same health topic, tell your prescriber, especially if the medicine is being adjusted to a target.

From our Q&A

Questions About Vitamin K or Tamoxifen Citrate

These are real questions from readers, answered by the pharmacists at HelloPharmacist — written by a person, not generated from a database. Each one covers Vitamin K or Tamoxifen Citrate, not necessarily both, but if one is close to what you were about to ask it will usually go further than a database entry can:

Not quite your question? Ask our pharmacists directly — it is free, there is no account required, and answers usually come back within 24 hours.

Everything else you take

See Every Supplement That Interacts With Tamoxifen Citrate

This page covers Vitamin K only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Tamoxifen Citrate page lists 210 supplements it has a documented interaction with, worst first, each one explained.

The most serious there right now: Activated Charcoal (major), American Hellebore (major), Arsenic (major), Beer (major) and Cesium (major).

By severity: 11 major · 166 moderate · 33 minor.

From our pharmacist’s overview on the Tamoxifen Citrate page

“Tamoxifen (Nolvadex, Soltamox) often stands between a breast cancer patient and a recurrence, so the stakes on this page run higher than usual. Eleven of the 210 supplements and herbs on file carry a major rating, and those eleven deserve your attention ahead of everything else.”

Reviewed by 2 · Jul 18, 2026

Open the Tamoxifen Citrate interaction page

One more smart check

Taking Vitamin K as Part of a Dietary Supplement Product? Check It for Interactions

We hold 5,292 real supplement products containing Vitamin K, each one broken down to its full ingredient list — and combination products often carry several ingredients besides Vitamin K. Even though Vitamin K itself has no known interaction with Tamoxifen Citrate, another ingredient on your label might. Find your product and we’ll check every ingredient on its label:

How much people look this up

Where Vitamin K and Tamoxifen Citrate Sit Against Everything Else

Out of every supplement and medication people look up on HelloPharmacist, here is where these two land this week — and which way each has been moving.

Supplement Vitamin K
Top 5%

#27 of 1,452 supplements looked up here in the last 7 days

29 days ago today
Medication Tamoxifen Citrate
Top 10%

#174 of 2,830 medications looked up here in the last 7 days

29 days ago today

Position among everything looked up on this site, not a measure of how commonly either one is used or how important it is. A supplement can climb this list because of a news story. It counts every request to the page, automated ones included, and nothing here identifies anyone.

Where does our data come from?
  • Source: the Natural Medicines (TRC Healthcare) clinical database — the evidence-graded professional reference for herb & supplement interactions.
  • Citation library: 103,510 references behind our interaction content, 65,311 of them resolved to verified PubMed/DOI sources. See every Vitamin K reference on this page ↓
  • Freshness: we automatically re-check this combination every week — this pair was last verified September 27, 2026. The Vitamin K and Tamoxifen Citrate records this page draws on were last updated July 10, 2026.
  • What “no known interaction” means: no documented interaction in the sources above — not a guarantee of safety. Supplements are studied far less than prescription drugs, so we say exactly what the evidence supports, and nothing more.
Data structure & sourcing designed and verified by .
Supplement

About Vitamin K

What is Vitamin K?

  • Supporting normal blood clotting
  • Bone health
  • Heart and vascular health
  • Correcting vitamin K deficiency
  • Newborn bleeding prevention (medical injection)

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 or bone and heart health, where evidence is mixed. If you take a blood thinner, talk to your pharmacist or doctor before changing your vitamin K intake.

Fat-soluble vitamin (K1 from plants, K2 from animal sources and bacteria) · Capsules, softgels, tablets, drops, injections (medical use)

An interaction check asks whether these two react with each other — it does not ask whether Vitamin K is a good idea for someone in your situation. Here is what our Vitamin K record says about it on its own.

Vitamin K: dosing

There is no single "best" supplement dose for everyone, and needs vary by age, sex, and health status. Nutrition authorities have set general daily intake recommendations for vitamin K that most people can meet through diet.If you choose to take a supplement, follow the directions on the product label and do not take more than recommended without medical advice.

From our Vitamin K monograph — the full record covers uses, side effects and every documented interaction.

Read the full Vitamin K monograph & all interactions
Medication

About Tamoxifen

What Is Tamoxifen Used For?

Brand names: Nolvadex, Soltamox

Tamoxifen is used to treat metastatic breast cancer (breast cancer that has spread) in both women and men, and as adjuvant (after-surgery) therapy for early-stage breast cancer in women. It also reduces the occurrence of cancer in the opposite breast when used as adjuvant therapy.

In women with ductal carcinoma in situ (DCIS) — a very early, non-invasive form of breast cancer — tamoxifen is used after breast surgery and radiation to reduce the risk of developing invasive breast cancer. It is also approved to reduce the incidence of breast cancer in women who are at high risk but have not yet been diagnosed. Soltamox (oral solution) is specifically indicated for all of these uses in adult patients.

See full Tamoxifen drug information
Keep checking

Other Drugs & Vitamin K

Browse every other medication we’ve checked against Vitamin K — both the ones with a known interaction and the ones without. Select any drug for the full detail.

2Major
0Moderate
0Minor
2,827No known interaction
2 Major 2,827 No interaction
Major

2 interactions

No interaction 2,827 drugs checked — show the list

We also checked Vitamin K against these medications and found no known interaction in our sources. Open any page to confirm.

Showing the 60 most looked-up of 2,827 medications checked with no known interaction — see the full Vitamin K list.

See the full Vitamin K interactions page
See every supplement checked against Tamoxifen Citrate, ranked by severity
Evidence & sources

Vitamin K References

The 11 references that drive our Vitamin K monograph and interaction data, from the evidence-graded Natural Medicines (TRC Healthcare) database. Citations with a link open the study on PubMed or the publisher’s site.

  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

Medication overviews come from MedlinePlus (NIH); supplement label data from the NIH Dietary Supplement Label Database. Content is written and reviewed by licensed HelloPharmacist pharmacists — see our data sources and editorial standards.

Pharmacist Counseling Corner

Taking Vitamin K and Tamoxifen Citrate Together: Common Questions

Is it safe to take Vitamin K with Tamoxifen Citrate?
We do not list a known interaction between Vitamin K and Tamoxifen Citrate. That does not guarantee the combination is risk-free, so confirm with your pharmacist or doctor — especially if you take other medications or have a health condition.
Do Vitamin K and Tamoxifen Citrate have any of the same side effects?
Yes — our sources link each of them separately to 7 of the same effects. That is not an interaction: neither changes how your body handles the other. It does mean that if one of those effects turns up, it can be harder to tell which one is behind it. They are listed on this page with the source behind each.
Are Vitamin K and Tamoxifen Citrate used for the same thing?
They overlap in purpose, which usually means the real question is whether you need both rather than whether they are safe together. This page lists the shared uses and how strong the evidence is for Vitamin K in each. That is a conversation for your prescriber, especially if Tamoxifen Citrate is being adjusted to a target.
How was the Vitamin K and Tamoxifen Citrate combination checked?
Interactions in our licensed database are recorded against drug classes. Tamoxifen Citrate is filed under 9 classifications, and Vitamin K has documented interactions with 1 drug class — none of Tamoxifen Citrate's classifications are among them. A medication can belong to classes beyond those recorded in our dataset, so this describes how the check was run rather than guaranteeing safety.
Does Vitamin K interact with any other medications?
Yes. Vitamin K has 2 documented drug interactions in our database — Tamoxifen Citrate is simply not one of them. If you take anything else, it is worth checking each one; they are all listed on this page.
Does Tamoxifen Citrate interact with any supplements?
Yes. Tamoxifen Citrate has documented interactions with 210 supplements in our database — Vitamin K is not one of them. The Tamoxifen Citrate interaction page linked on this page lists every one, ranked by severity.

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

Where next

Keep Exploring

Vitamin K monograph Uses, safety profile, and every drug interaction in one place Tamoxifen drug information The full plain-English guide to this medication Tamoxifen Citrate supplement interactions Every supplement checked against Tamoxifen Citrate, ranked by severity Supplement interaction checker Check any supplement or product against your medications Browse medications A–Z Every drug we’ve checked against herbs & supplements References The 11 citations behind this page Ask a pharmacist Free, personal answer from our licensed team

Still Have a Question About Tamoxifen Citrate and Vitamin K?

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This information is for education only and is not a substitute for professional medical advice. Always check with your pharmacist or doctor before starting, stopping, or combining supplements and medications.