Drug & supplement interaction

Alfalfa + Levonorgestrel

Levonorgestrel brand names: Plan B, Mirena, Levonelle One Step, Levonelle 1500, Norgeston, and others.

Moderate Interaction
Medically reviewed by · Updated September 2026
The bottom line Moderate

Alfalfa has a moderate interaction with Levonorgestrel. Theoretically, alfalfa might interfere with the activity of contraceptive drugs.

Read the full interaction report
SeverityModerate
LikelihoodPossible
EvidenceD
What do Severity, Likelihood & Evidence mean?
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Interaction report

Alfalfa and Levonorgestrel

Here is the interaction we found between these two, with the evidence behind it.

Moderate

CONTRACEPTIVE DRUGS

Why this applies to Levonorgestrel

Levonorgestrel falls under CONTRACEPTIVE DRUGS — the group Alfalfa interacts with.

Theoretically, alfalfa might interfere with the activity of contraceptive drugs.
Alfalfa contains coumestrol, a phytoestrogen, and isoflavonoids, which have estrogenic effects.
Severity Moderate Likelihood Possible Evidence D

Interaction has been documented in animal or in lab research, or the interaction has been documented in humans but is limited to case reports or conflicting clinical research exists.

Dr. Brian Staiger, PharmD, BCPS
Dr. Brian Staiger explains PharmD, Clinical Pharmacist

Here's the thinking behind this one. Alfalfa supplements contain plant compounds called phytoestrogens (like coumestrol) that act weakly like your body's own estrogen. The concern is that these estrogen-like signals could, in theory, work against how a hormone-based contraceptive like levonorgestrel (Plan B, Mirena) is meant to do its job. Levonorgestrel is an active progestin, not a prodrug, so it doesn't need to be switched on by your body to work.

I want to be honest about the strength here: this is theoretical, based on lab pharmacology rather than real cases of failed contraception. Food amounts of alfalfa sprouts are very unlikely to matter; concentrated supplements are the bigger question mark. If you rely on levonorgestrel, especially Mirena, just check with your pharmacist or doctor before adding alfalfa.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Newall CA, Anderson LA, Philpson JD. Herbal Medicine: A Guide for Healthcare Professionals. London, UK: The Pharmaceutical Press, 1996.
  2. Elakovich, S. D. and Hampton, J. M. Analysis of coumestrol, a phytoestrogen, in alfalfa tablets sold for human consumption. J Agric.Food Chem. 1984;32(1):173-175. PubMed

What These Ratings Mean

Every interaction above is graded three ways — here’s the key to each label.

Severity how clinically significant the interaction is
Major

Clinically significant. Avoid the combination, or use only under close professional supervision.

Moderate

Usually worth avoiding or managing — may need monitoring, a dose change, or timing apart.

Minor

Generally not serious. Be aware of it and mention it to your pharmacist.

Likelihood how strong the evidence is that the interaction actually happens in people
  • LikelyWell-controlled human studies have demonstrated the likely existence of this interaction.
  • ProbableInteraction has not been documented in well-controlled studies, however, the interaction has been demonstrated in some small human studies or in controlled animal studies in conjunction with multiple case reports.
  • PossibleInteraction has been documented in animal or in lab research, or the interaction has been documented in humans but is limited to case reports or conflicting clinical research exists.
  • UnlikelyInteraction has been demonstrated in animal or in lab research but has been shown not to occur in humans.
Evidence the quality of the studies behind the rating (graded A–D)
  • AHigh-quality meta-analysis (quantitative systematic review).
  • BCase-control study.
  • CConsensus.
  • DAnecdotal evidence.

These ratings are for information only. Never start, stop, or otherwise change your therapy before speaking with your provider.

Keep it in perspective

Alfalfa Also Interacts With Other Medications

Alfalfa has 2 major, 580 moderate known drug interactions in our database — the Levonorgestrel one above is one of them. If you take anything else, check it against the full list below.

Major 2 Moderate 580 No known interaction 2,248 (incl. Levonorgestrel)
Taking anything else?

Check Another of Your Medications Against Alfalfa

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

From our Q&A

Questions About Alfalfa or Levonorgestrel

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

This page covers Alfalfa only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Levonorgestrel page lists 191 supplements it has a documented interaction with, worst first, each one explained.

The most serious there right now: Activated Charcoal (major), Beer (major), Grapefruit (major), Siberian Cocklebur (major) and St. John's Wort (major).

By severity: 6 major · 142 moderate · 43 minor.

From our pharmacist’s overview on the Levonorgestrel page

“St. John's wort tops my worry list for anyone using levonorgestrel (Plan B, Mirena, and other birth control).”

Reviewed by 2 · Jul 18, 2026

Open the Levonorgestrel interaction page

One more smart check

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

We hold 3,559 real supplement products containing Alfalfa, each one broken down to its full ingredient list — and combination products often carry several ingredients besides Alfalfa. Your product may carry other ingredients that interact with Levonorgestrel too, on top of Alfalfa — and those would not show on this page. Find your product and we’ll check every ingredient on its label:

How much people look this up

Where Alfalfa and Levonorgestrel 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 Alfalfa
Top 10%

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

29 days ago today
Medication Levonorgestrel
Top 25%

#405 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.

Supplement

About Alfalfa

What is Alfalfa?

Alfalfa
  • High cholesterol
  • Digestive complaints
  • Menopausal symptoms
  • Arthritis and joint pain
  • General nutritional supplement

Alfalfa is a nutrient-rich legume that people use for high cholesterol, menopause symptoms, and general wellness, but solid human evidence for most of these uses is limited. It is best avoided by people with autoimmune diseases, those who are pregnant or breastfeeding, and anyone with a weakened immune system, and you should check with your pharmacist or doctor before trying it.

Read the full Alfalfa monograph & all interactions
Medication

About Levonorgestrel

What Is Levonorgestrel Used For?

Brand names: Plan B, Mirena, Levonelle One Step, Levonelle 1500, Norgeston, Skyla, Liletta, Kyleena

Levonorgestrel is used in two very different ways depending on the product. As an intrauterine system (IUS), Mirena and Liletta prevent pregnancy for up to 8 years and also treat heavy menstrual bleeding for up to 5 years in people who choose intrauterine contraception. Kyleena prevents pregnancy for up to 5 years, and Skyla prevents pregnancy for up to 3 years — neither Kyleena nor Skyla is indicated for heavy menstrual bleeding.

As an oral tablet, products such as AfterPill, AfterPlan, Amazon Basic Care Levonorgestrel, Econ Morning After, Emergency Contraceptive, and Empowered Choice are used as emergency (backup) contraception to reduce the chance of pregnancy after unprotected sex or contraceptive failure. The oral tablet is not intended for routine birth control.

See full Levonorgestrel drug information
Keep checking

Other Drugs & Alfalfa

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

2Major
580Moderate
0Minor
2,247No known interaction
2 Major 580 Moderate 2,247 No interaction
Major

2 interactions

Moderate

580 interactions

Showing 60 of 580 moderate interactions — see all 580 on the Alfalfa page.

No interaction 2,247 drugs checked — show the list

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

Showing the 60 most looked-up of 2,247 medications checked with no known interaction — see the full Alfalfa list.

See the full Alfalfa interactions page
See every supplement checked against Levonorgestrel, ranked by severity
Sources

Sources & How We Checked

Interaction details are evidence-graded and sourced from the Natural Medicines database. The medication overview comes from MedlinePlus.

Content is written and reviewed by licensed HelloPharmacist pharmacists. See our data sources and editorial standards for how this information is built and checked.

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

Keep exploring
Alfalfa monograph › Uses, safety, and every drug interaction in one place Levonorgestrel supplement interactions › Every supplement checked against Levonorgestrel, ranked by severity Levonorgestrel drug information › The full plain-English guide to this medication Supplement interaction checker › Check any supplement or product against your medications Browse medications A–Z › Every drug we've checked against herbs & supplements Ask a pharmacist › Free, personal answer from our licensed team
Pharmacist Counseling Corner

Taking Alfalfa and Levonorgestrel Together: Common Questions

Can you take Alfalfa with Levonorgestrel?
There is a moderate interaction, so it may be acceptable with monitoring or timing changes — but check with your pharmacist first. Read the full details on this page and confirm with your pharmacist before combining them.
How serious is the Alfalfa and Levonorgestrel interaction?
We rate it Moderate. This combination may require monitoring, a dose adjustment, or separating the times you take each one. Consult your pharmacist before using them together.

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

Still Have a Question About Levonorgestrel and Alfalfa?

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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.