Drug & supplement interaction

Vitamin K + Letermovir (IV)

Letermovir (IV) brand name: Prevymis.

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 Letermovir (IV) 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 Letermovir (IV)

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 Letermovir (IV) 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 Letermovir (IV) and Vitamin K? Ask Dr. Brian Staiger, PharmD, BCPS directly ›
Keep it in perspective

Vitamin K Does Interact With Other Medications

Vitamin K has 2 major, known drug interactions in our database — Letermovir (IV) 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. Letermovir (IV))
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 Letermovir (IV) 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. One of them is worth acting on rather than waiting out — marked below.

  • An 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

    Letermovir (IV)

    Listed in the ADVERSE REACTIONS section of the FDA label for Letermovir (IV). 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

    Letermovir (IV)

    Listed in the ADVERSE REACTIONS section of the FDA label for Letermovir (IV). Read the label on DailyMed ›

  • Diarrhea / Nausea Additional detail

    Vitamin K

    “Orally, vitamin K is generally well tolerated.

    Most Common Adverse Effects:

    Orally: Diarrhea, nausea, and stomach upset.

    Serious Adverse Effects (Rare):

    Intravenously: There have been rare cases of anaphylaxis and hyperbilirubinemia (in infants).”

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

    Letermovir (IV)

    Listed in the ADVERSE REACTIONS section of the FDA label for Letermovir (IV). Read the label on DailyMed ›

Reported for Vitamin K but not commonly for Letermovir (IV): liver problems, stomach upset, a severe allergic reaction and yellowing of the skin or eyes.

Effects for Letermovir (IV) 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 Letermovir (IV) 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. Letermovir (IV) 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.

Letermovir (IV) is prescribed for: Prevymis injection is used to prevent cytomegalovirus (CMV) infection and disease in adults and children 6 months of age and older (weighing at least 6 kg) who have received an allogeneic hematopoietic stem cell transplant (HSCT) and are CMV-seropositive (meaning they carry the CMV virus). Prevymis injection is also used to prevent CMV disease in adults and children 12 years of age and older (weighing at least 40 kg) who have received a kidney transplant and are at high risk — specifically when the donor tested positive for CMV but the recipient tested negative (D+/R-).

Vitamin K has been studied for:

  • Kidney transplant 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 kidney transplant

    It is unclear if vitamin K is beneficial for reducing cardiovascular risk in kidney transplant recipients.

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 Letermovir (IV) 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.

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 Letermovir (IV), 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 Letermovir (IV) 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 Letermovir (IV)
Top 25%

#322 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 Letermovir (IV) 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 Letermovir Injection

What Is Letermovir Injection Used For?

Brand name: Prevymis

Prevymis injection is used to prevent cytomegalovirus (CMV) infection and disease in adults and children 6 months of age and older (weighing at least 6 kg) who have received an allogeneic hematopoietic stem cell transplant (HSCT) and are CMV-seropositive (meaning they carry the CMV virus).

Prevymis injection is also used to prevent CMV disease in adults and children 12 years of age and older (weighing at least 40 kg) who have received a kidney transplant and are at high risk — specifically when the donor tested positive for CMV but the recipient tested negative (D+/R-).

See full Letermovir Injection 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 Letermovir (IV), 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 Letermovir (IV) Together: Common Questions

Is it safe to take Vitamin K with Letermovir (IV)?
We do not list a known interaction between Vitamin K and Letermovir (IV). 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 Letermovir (IV) have any of the same side effects?
Yes — our sources link each of them separately to 4 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 Letermovir (IV) 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 Letermovir (IV) is being adjusted to a target.
Does Vitamin K interact with any other medications?
Yes. Vitamin K has 2 documented drug interactions in our database — Letermovir (IV) is simply not one of them. If you take anything else, it is worth checking each one; they are all listed on this page.

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 Letermovir Injection drug information The full plain-English guide to this medication Letermovir (IV) supplement interactions Every supplement checked against Letermovir (IV), 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 Letermovir (IV) 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.