Drug & supplement interaction

Comfrey + Niacin (prescription drug)

Niacin (prescription drug) brand names: Niaspan, Niacor.

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

Comfrey has a moderate interaction with Niacin (prescription drug). 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 Niacin (prescription drug)

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

Moderate

HEPATOTOXIC DRUGS

Why this applies to Niacin (prescription drug)

Niacin (prescription drug) 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 concern with pairing comfrey and prescription niacin: both can be tough on your liver. Niacin, especially at the higher doses used to manage cholesterol, is already known to occasionally raise liver enzymes and, rarely, cause more serious liver trouble. Comfrey contains pyrrolizidine alkaloids, natural compounds that can also injure the liver, which is why it should never be swallowed and only used briefly on intact skin.

Put them together and the worry is that the liver strain could add up. This is a theoretical caution based on how each one behaves, not on proven cases, so don't panic. Still, watch for warning signs like yellowing skin or eyes, dark urine, belly pain, or unusual fatigue, and check with your pharmacist or doctor before combining them.

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 437 moderate known drug interactions in our database — the Niacin (prescription drug) one above is one of them. If you take anything else, check it against the full list below.

Moderate 437 No known interaction 2,393 (incl. Niacin (prescription drug))
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 Niacin (prescription drug)

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 Niacin (prescription drug), 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 Niacin (prescription drug)

This page covers Comfrey only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Niacin (prescription drug) page lists 60 supplements it has a documented interaction with, worst first, each one explained.

The most serious there right now: Activated Charcoal (major), Beer (major), Siberian Cocklebur (major), Wine (major) and Ashwagandha (moderate).

By severity: 4 major · 43 moderate · 13 minor.

From our pharmacist’s overview on the Niacin (prescription drug) page

“Prescription niacin (Niaspan, Niacor) is dosed high enough for cholesterol treatment that it can strain the liver all by itself, so this is a list to treat seriously rather than skim. Thirty-eight of the 60 interacting supplements and herbs can add their own liver stress, and alcohol leads that group, with beer and wine accounting for…”

Reviewed by 2 · Jul 18, 2026

Open the Niacin (prescription drug) 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 Niacin (prescription drug) 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 Niacin (prescription drug) 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

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

29 days ago today
Medication Niacin (prescription drug)
Top half

#1,354 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 Niacin

What Is Niacin Used For?

Brand names: Niaspan, Niacor

Niacin is used alongside diet changes to lower high LDL (bad) cholesterol and triglycerides, and to raise HDL (good) cholesterol in adults with primary hyperlipidemia (high cholesterol) or mixed dyslipidemia (abnormal levels of several blood fats). It is also used to treat adults with very high triglyceride levels who are at risk of pancreatitis (dangerous inflammation of the pancreas) when diet alone hasn't worked.

Niacin extended-release tablets are additionally indicated to reduce the risk of a repeat nonfatal heart attack in patients who have already had a heart attack and also have high cholesterol. When used together with a bile acid binding resin, niacin extended-release tablets can slow or even reverse the buildup of plaque in the arteries (atherosclerosis) in patients with coronary artery disease and high cholesterol. Niacin is always used as part of a broader treatment plan — not as a standalone solution.

See full Niacin 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
437Moderate
0Minor
2,392No known interaction
437 Moderate 2,392 No interaction
Moderate

437 interactions

Showing 60 of 437 moderate interactions — see all 437 on the Comfrey page.

No interaction 2,392 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 2,392 medications checked with no known interaction — see the full Comfrey list.

See the full Comfrey interactions page
See every supplement checked against Niacin (prescription drug), 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
Comfrey monograph › Uses, safety, and every drug interaction in one place Niacin (prescription drug) supplement interactions › Every supplement checked against Niacin (prescription drug), ranked by severity Niacin 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 Comfrey and Niacin (prescription drug) Together: Common Questions

Can you take Comfrey with Niacin (prescription drug)?
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 Niacin (prescription drug) 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 Niacin (prescription drug) 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.