Drug & supplement interaction

Vitamin K + Letrozole, Ribociclib Succinate

Letrozole, Ribociclib Succinate brand name: Kisqali Femara Co-Pack.

No Known Interaction
Medically reviewed by · Updated July 2026 · Pair last verified Sep 13, 2026
The bottom line No known interaction

We found no known interaction between Vitamin K and Letrozole, Ribociclib Succinate 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.

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Interaction report

Vitamin K and Letrozole, Ribociclib Succinate

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 Letrozole, Ribociclib Succinate 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 Letrozole, Ribociclib Succinate and Vitamin K? Ask Dr. Brian Staiger, PharmD, BCPS directly ›
How we checked

Why No Interaction Is Listed for Letrozole, Ribociclib Succinate

Interactions in our licensed database are recorded against drug classes, not just single drug names. Letrozole, Ribociclib Succinate is filed under 6 classifications — including aromatase inhibitors, cytochrome p450 2c19 (cyp2c19) inhibitors, qt interval-prolonging drugs. Vitamin K has documented interactions with 1 drug class — the most serious being warfarin (coumadin) (major) — and none of Letrozole, Ribociclib Succinate’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 — Letrozole, Ribociclib Succinate 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. Letrozole, Ribociclib Succinate)
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

What Vitamin K Itself Has Been Linked To

This is not an interaction — nothing below involves Letrozole, Ribociclib Succinate. It is the side-effect record for Vitamin K on its own, from the licensed Natural Medicines monograph. If something new turns up after you add Vitamin K, this list is the first place to look. 3 entries are worth acting on rather than waiting out — marked below.

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

    “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.
  • A severe allergic reaction Worth acting on Additional detail

    “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
  • An allergic reaction Worth acting on Additional detail

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

  • Stomach upset Additional detail

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

  • Stomach pain Additional detail

    “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
  • Diarrhea / Nausea Additional detail

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

Everything above comes from the Natural Medicines adverse-effect record for Vitamin K — expand a row for the licensed statement it rests on. We haven’t matched Letrozole, Ribociclib Succinate to its FDA label in our system yet, so we can’t compare its own side-effect list here — the leaflet that comes with your prescription is the authoritative list for Letrozole, Ribociclib Succinate.

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

Everything else you take

See Every Supplement That Interacts With Letrozole, Ribociclib Succinate

This page covers Vitamin K only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Letrozole, Ribociclib Succinate page lists 155 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), Cesium (major) and Ephedra (major).

By severity: 8 major · 109 moderate · 38 minor.

From our pharmacist’s overview on the Letrozole, Ribociclib Succinate page

“Grapefruit tops my worry list for anyone taking the Kisqali Femara Co-Pack (letrozole and ribociclib), because it blocks the enzyme, CYP3A4, that clears ribociclib and can push levels of this breast cancer drug higher than intended. That enzyme thread runs through 121 of the 155 ingredients on this page, and with eight rated major, rea…”

Reviewed by 2 · Jul 18, 2026

Open the Letrozole, Ribociclib Succinate 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 Letrozole, Ribociclib Succinate, 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 Letrozole, Ribociclib Succinate 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%

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

29 days ago today
Medication Letrozole, Ribociclib Succinate
Top 25%

#404 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 13, 2026. The Vitamin K and Letrozole, Ribociclib Succinate 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
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 Letrozole, Ribociclib Succinate, 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 Letrozole, Ribociclib Succinate Together: Common Questions

Is it safe to take Vitamin K with Letrozole, Ribociclib Succinate?
We do not list a known interaction between Vitamin K and Letrozole, Ribociclib Succinate. 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.
How was the Vitamin K and Letrozole, Ribociclib Succinate combination checked?
Interactions in our licensed database are recorded against drug classes. Letrozole, Ribociclib Succinate is filed under 6 classifications, and Vitamin K has documented interactions with 1 drug class — none of Letrozole, Ribociclib Succinate'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 — Letrozole, Ribociclib Succinate 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 Letrozole, Ribociclib Succinate interact with any supplements?
Yes. Letrozole, Ribociclib Succinate has documented interactions with 155 supplements in our database — Vitamin K is not one of them. The Letrozole, Ribociclib Succinate 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 Letrozole, Ribociclib Succinate supplement interactions Every supplement checked against Letrozole, Ribociclib Succinate, 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

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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.