Drug & supplement interaction

Multivitamins + Letrozole

Letrozole brand name: Femara.

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 Multivitamins and Letrozole 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.

Know someone taking this? Share
Facebook Post Reddit Email
On this page
Interaction report

Multivitamins and Letrozole

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 and Multivitamins 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.

Worth understanding: our licensed dataset holds no drug-interaction record for Multivitamins at all — not against Letrozole, and not against any other medication we track. This verdict therefore rests on the absence of any recorded data, not on research that looked at this combination and found nothing. We cannot rule an interaction out.

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.

Multivitamins safety at a glance

Multivitamins overall Generally safe Standard multivitamins are generally safe for most people when taken as directed.
Pregnancy Use caution Use a prenatal product chosen with your provider, and avoid high-dose vitamin A from non-prenatal multivitamins.
Breastfeeding Likely Safe When multivitamins specifically formulated for pregnancy or lactation are used orally and appropriately. A multivitamin containing nutrients in amounts that do... 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 and Multivitamins? Ask Dr. Brian Staiger, PharmD, BCPS directly ›
What to actually watch for

What Multivitamins Itself Has Been Linked To

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

  • A bowel blockage Worth acting on Additional detail

    “Orally, a case of pharmacobezoar with resultant large bowel obstruction due to multivitamin consumption is reported in a 77-year-old patient with a history of chronic constipation and anatomic abnormality of the colon.”

    Multivitamins · Natural Medicines adverse-effect record, reported in constipation.

    1 source cited
    1. 111624. Burgos-Torres MDM, Molina-Lopez VH, Perez Cruz NM, Perez Del Valle C, Sorrentino J. Multivitamin-Induced Pharmacobezoar: A Rare Entity of Large Bowel Obstruction. Cureus 2023;15(7):e41688. PubMed
  • Constipation Additional detail

    Recorded for Multivitamins in the same Natural Medicines adverse-effect record shown under A bowel blockage above.

Everything above comes from the Natural Medicines adverse-effect record for Multivitamins — expand a row for the licensed statement it rests on. We read the ADVERSE REACTIONS section of Letrozole’s FDA label too, and the two lists don’t meaningfully overlap — which is why no Letrozole column appears here.

Special populations

Multivitamins in Pregnancy & Breastfeeding

Lactation Likely Safe

When multivitamins specifically formulated for pregnancy or lactation are used orally and appropriately. A multivitamin containing nutrients in amounts that do not exceed Dietary Reference Intakes (DRIs) during pregnancy or lactation should be safe in this population. Keep in mind that people consuming other sources of nutrients in addition to a multivitamin should use caution not to exceed tolerable upper intake levels (ULs) of these nutrients. Consuming nutrients in amounts above the ULs increases the risk of adverse effects. See the Prenatal Vitamins monograph for information about multivitamins specifically formulated for use during pregnancy.

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 Letrozole Is Prescribed For, and What Multivitamins Has Been Studied For

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

Letrozole is prescribed for: Letrozole (brand name Femara) is used to treat breast cancer in postmenopausal women whose tumors are driven by estrogen. It is used in three settings: as adjuvant (after-surgery) treatment for hormone receptor positive early breast cancer; as extended adjuvant treatment for women who have already completed about five years of tamoxifen therapy; and as first- or second-line treatment for locally advanced or metastatic (spread) breast cancer. Femara is specifically indicated for first-line treatment of hormone receptor positive or receptor-unknown locally advanced or metastatic breast cancer, and for advanced breast cancer in women whose disease has progressed after antiestrogen therapy.

Multivitamins has been studied for:

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

    Multivitamins for breast cancer

    It is unclear if oral multivitamins are beneficial for preventing 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 Letrozole on your own; if you are taking Multivitamins for the same health topic, tell your prescriber, especially if the medicine is being adjusted to a target.

From our Q&A

Questions About Multivitamins or Letrozole

These are real questions from readers, answered by the pharmacists at HelloPharmacist — written by a person, not generated from a database. Each one covers Multivitamins or Letrozole, 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 Letrozole

This page covers Multivitamins only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Letrozole page lists 142 supplements it has a documented interaction with, worst first, each one explained.

The most serious there right now: Activated Charcoal (major), Grapefruit (major), St. John's Wort (major), 7-methoxyflavone (moderate) and Acacia Rigidula (moderate).

By severity: 3 major · 99 moderate · 40 minor.

From our pharmacist’s overview on the Letrozole page

“Letrozole (Femara) is prescribed to keep hormone-driven breast cancer from returning, so a supplement that shifts its blood level can quietly undercut treatment. Give this list of 142 ingredients genuine respect, and learn the three major entries first.”

Reviewed by 2 · Jul 18, 2026

Open the Letrozole interaction page

How much people look this up

Where Multivitamins and Letrozole 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 Multivitamins
Steady interest

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

29 days ago today
Medication Letrozole
Top 5%

#50 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 Multivitamins reference on this page ↓
  • Freshness: we automatically re-check this combination every week — this pair was last verified September 13, 2026. The Multivitamins and Letrozole records this page draws on were last updated July 11, 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 Multivitamins

What is Multivitamins?

  • Filling nutrient gaps in the diet
  • General wellness support
  • Pregnancy nutrition (with prenatal versions)
  • Supporting older adults' nutrition
  • Energy and immune support (popular belief)

Multivitamins are combination supplements that provide many vitamins and minerals in one product, and they can help cover nutrient gaps for people who don't get enough from food. For most healthy adults who eat a balanced diet, the proven health benefits are modest, but certain groups—such as pregnant people, older adults, and those with restricted diets—may benefit more. Talk with your pharmacist or doctor to choose a product that fits your needs and avoid taking too much of any single nutrient.

Tablets, capsules, gummies, chewables, liquids, powders

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

Multivitamins: dosing

There is no single "correct" dose for multivitamins because each product contains a different mix of nutrients. Most are designed to provide amounts at or near the recommended daily intake for common vitamins and minerals.The best approach is to follow the directions on the product label and not take more than one daily serving unless told to by a healthcare provider. Avoid combining several supplements that contain the same nutrients, since this can push you above safe limits.Your pharmacist can help you pick a product matched to your age, sex, and health needs, and check that it won't overlap with other supplements you take.

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

Read the full Multivitamins monograph & all interactions
Medication

About Letrozole

What Is Letrozole Used For?

Brand name: Femara

Letrozole (brand name Femara) is used to treat breast cancer in postmenopausal women whose tumors are driven by estrogen. It is used in three settings: as adjuvant (after-surgery) treatment for hormone receptor positive early breast cancer; as extended adjuvant treatment for women who have already completed about five years of tamoxifen therapy; and as first- or second-line treatment for locally advanced or metastatic (spread) breast cancer.

Femara is specifically indicated for first-line treatment of hormone receptor positive or receptor-unknown locally advanced or metastatic breast cancer, and for advanced breast cancer in women whose disease has progressed after antiestrogen therapy.

See full Letrozole drug information
Keep checking

Other Drugs & Multivitamins

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

0Major
0Moderate
0Minor
2,829No known interaction
2,829 No interaction
No interaction 2,829 drugs checked — show the list

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

Showing the 60 most looked-up of 2,829 medications checked with no known interaction — see the full Multivitamins list.

See the full Multivitamins interactions page
See every supplement checked against Letrozole, ranked by severity
Evidence & sources

Multivitamins References

The 2 references that drive our Multivitamins 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. Multivitamin/mineral Supplements Fact Sheet for Health Professionals. National Institutes of Health - Office of Dietary Supplements. July 8, 2015. https://ods.od.nih.gov/factsheets/MVMS-HealthProfessional/. Accessed March 18, 2018.
  2. Burgos-Torres MDM, Molina-Lopez VH, Perez Cruz NM, Perez Del Valle C, Sorrentino J. Multivitamin-Induced Pharmacobezoar: A Rare Entity of Large Bowel Obstruction. Cureus 2023;15(7):e41688. 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 Multivitamins and Letrozole Together: Common Questions

Is it safe to take Multivitamins with Letrozole?
We do not list a known interaction between Multivitamins and Letrozole. 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.
Are Multivitamins and Letrozole 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 Multivitamins in each. That is a conversation for your prescriber, especially if Letrozole is being adjusted to a target.
Does Letrozole interact with any supplements?
Yes. Letrozole has documented interactions with 142 supplements in our database — Multivitamins is not one of them. The Letrozole 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

Multivitamins monograph Uses, safety profile, and every drug interaction in one place Letrozole drug information The full plain-English guide to this medication Letrozole supplement interactions Every supplement checked against Letrozole, 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 2 citations behind this page Ask a pharmacist Free, personal answer from our licensed team

Still Have a Question About Letrozole and Multivitamins?

Our pharmacists answer your medication & supplement questions — free.

Ask a pharmacist

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.