Drug & supplement interaction

Comfrey + Levonorgestrel

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

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

Comfrey has a moderate interaction with Levonorgestrel. Theoretically, comfrey might have additive adverse effects on the liver when used with hepatotoxic drugs.

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

Comfrey and Levonorgestrel

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

Moderate

HEPATOTOXIC DRUGS

Why this applies to Levonorgestrel

Levonorgestrel falls under HEPATOTOXIC DRUGS — the group Comfrey interacts with.

Theoretically, comfrey might have additive adverse effects on the liver when used with hepatotoxic drugs.
Due to its pyrrolizidine alkaloid constituents, comfrey can cause hepatotoxic effects, including ascites, cirrhosis, hepatic fibrosis, hepatomegaly, and sinusoidal obstruction syndrome.
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 situation with comfrey and levonorgestrel (like Plan B or Mirena). The concern here isn't that comfrey changes how well your birth control works. Instead, it's about your liver. Comfrey contains compounds called pyrrolizidine alkaloids that can be hard on the liver, especially when taken by mouth. Levonorgestrel is also processed through the liver, so the worry is a possible added strain on that organ.

I'll be honest with you: this is a theoretical concern based on how these substances behave, not something proven to happen with this combo. Still, comfrey should never be swallowed. If you're using a topical comfrey product on intact skin briefly, the risk is much lower. When in doubt, check with your pharmacist or doctor.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Food and Drug Administration. FDA Advises Dietary Supplement Manufacturers to Remove Comfrey Products From the Market. July 6, 2001. Available at: http://www.cfsan.fda.gov/~dms/dspltr06.html.
  2. Stickel F, Seitz HK. The efficacy and safety of comfrey. Public Health Nutr 2000;3:501-8. 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

Comfrey Also Interacts With Other Medications

Comfrey has 439 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.

Moderate 439 No known interaction 2,391 (incl. Levonorgestrel)
Taking anything else?

Check Another of Your Medications Against Comfrey

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

From our Q&A

Questions About Comfrey 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 Comfrey 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 Comfrey 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 Comfrey as Part of a Dietary Supplement Product? Check It for Interactions

We hold 29 real supplement products containing Comfrey, each one broken down to its full ingredient list — and combination products often carry several ingredients besides Comfrey. Your product may carry other ingredients that interact with Levonorgestrel too, on top of Comfrey — 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 Comfrey 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 Comfrey
Top half

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

29 days ago today
Medication Levonorgestrel
Top 25%

#452 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 Comfrey

What is Comfrey?

Comfrey
  • Bruises and sprains
  • Muscle and joint pain
  • Minor wounds and skin irritation
  • Back pain
  • Inflammation

Comfrey is a traditional herb used mainly on the skin for bruises, sprains, and joint pain, and some topical products show modest benefit for these uses. However, comfrey contains compounds that can seriously damage the liver, so it should never be taken by mouth and should only be used on unbroken skin for short periods. Pregnant or breastfeeding people should avoid it entirely.

Read the full Comfrey 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.

The intrauterine systems (Mirena, Liletta, Kyleena and Skyla) prevent pregnancy for a set number of years. Mirena and Liletta are also used to treat heavy menstrual bleeding in women who choose intrauterine contraception. The oral tablets are used for emergency contraception, to reduce the chance of pregnancy after unprotected sex.

See full Levonorgestrel drug information
Keep checking

Other Drugs & Comfrey

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

0Major
439Moderate
0Minor
2,390No known interaction
439 Moderate 2,390 No interaction
Moderate

439 interactions

Showing 60 of 439 moderate interactions — see all 439 on the Comfrey page.

No interaction 2,390 drugs checked — show the list

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

Showing the 60 most looked-up of 2,390 medications checked with no known interaction — see the full Comfrey list.

See the full Comfrey 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
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Pharmacist Counseling Corner

Taking Comfrey and Levonorgestrel Together: Common Questions

Can you take Comfrey 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 Comfrey 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 Comfrey?

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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.