Herb & supplement monograph

Black Root Drug Interactions, Uses, Safety & More

Medically reviewed by Dr. Brian Staiger, PharmD, BCPS ·Updated July 2026

What is this page for?

First and foremost: how Black Root interacts with medications. The heart of this page is the interaction list — every drug Black Root is known to interact with, and how serious each one is.

But these pages have grown well beyond that into a full monograph — what Black Root is, what people use it for and how strong the evidence is, its safety and side effects, and answers to the questions we’re asked most — written and reviewed by the clinical staff at HelloPharmacist. It’s educational information from our licensed clinical databases, not medical advice, and we don’t sell or endorse products. Our editorial policy

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Black Root Drug Interactions: The Bottom Line

From the HelloPharmacist Editorial Team · Updated July 2026

Based on the available evidence, the overall risk of a clinically significant Black Root drug interaction appears low for most people who use it in normal amounts. None of the listed interactions are rated major, and the concerns that do exist are mostly theoretical or tied to overuse of the herb.

Interactions deserving the most attention

The best-documented concern is with digoxin, since black root may bind to this heart medicine in the gut and make it less effective. With warfarin, the herb's laxative effect can cause diarrhea, which may raise INR and increase bleeding risk, so heavy use is the main worry. There is also some concern that overusing black root alongside potassium-depleting diuretics could add to potassium loss, and some people may need their potassium watched more closely.

What the rest of the list means

Dozens of medications appear on this list, but that mostly reflects how many drugs fall into these few broad groups, not proof that each combination is harmful. Most of the concerns are theoretical or come from limited evidence, and they generally depend on taking large amounts of black root or on its laxative effect rather than on confirmed problems in people using it moderately.

Check your medications against Black Root

Based on HelloPharmacist’s Black Root interaction data and reviewed under our editorial standards.

Interaction report

Drugs that interact with Black Root

78 medications have a known interaction with Black Root, graded by severity. Select any drug for the full evidence-based detail.

Don’t want to scroll the list? Just ask.

Tell us the medications you take and we’ll check each one against Black Root using our pharmacist-reviewed interaction data.

AI summaries are generated from our Black Root interaction data for education only — always confirm with your pharmacist. How we use AI

2,830 drugs

Read The List Like a Pharmacist

What Severity, Likelihood & Evidence Mean

Severity — How Serious It Can Be

Major. Clinically significant; generally best avoided, or used only under direct professional supervision.
Moderate. May need monitoring, a dose adjustment, or separating the times you take each one.
Minor. Generally not clinically significant, but still worth noting and mentioning to your pharmacist.
No known interaction. Checked against our sources with nothing documented — not the same as proven safety.

Likelihood — How Well It’s Documented

Likely. Well-controlled human studies have demonstrated the likely existence of this interaction
Probable. Interaction 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.
Possible. 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
Unlikely. Interaction has been demonstrated in animal or in lab research but has been shown not to occur in humans.

Where This Data Comes From

Interaction records are evidence-graded and sourced from the Natural Medicines database (TRC Healthcare), the same reference used by pharmacists and hospitals.
Each drug listed above links to the full report for that exact Black Root combination — clinical detail, likelihood, evidence level, and citations.
Content is reviewed by licensed HelloPharmacist pharmacists — see our data sources and editorial standards.

The big picture

The kinds of drugs Black Root affects

Every type of medication (drug category) Black Root is known to interact with. Open any category for the detail — or search your exact drug in the checker above.

All 3 drug categories Black Root interacts with

Digoxin (lanoxin)Diuretic DrugsWarfarin (coumadin)

Digoxin (Lanoxin)

Theoretically, the overuse or abuse of black root can increase the risk of adverse effects of cardiac glycoside drugs. Black root chemically binds with the glycosides while in the gastrointestinal (GI) tract, which may reduce their effectiveness if used concomitantly.

Likelihood Probable Evidence D

Diuretic Drugs

Overuse of black root might compound diuretic-induced potassium loss.There is some concern that people taking black root along with potassium depleting diuretics might have an increased risk for hypokalemia. Initiation of potassium supplementation or an increase in potassium supplement dose may be necessary for some patients. Some diuretics that can deplete potassium include chlorothiazide (Diuril), chlorthalidone (Thalitone), furosemide (Lasix), hydrochlorothiazide (HCTZ, Hydrodiuril, Microzide), and others.

Likelihood Possible Evidence D

Warfarin (Coumadin)

Black root has stimulant laxative effects. In some people black root can cause diarrhea. Diarrhea can increase the effects of warfarin, increase international normalized ratio (INR), and increase the risk of bleeding. Advise patients who take warfarin not to take excessive amounts of black root.

Likelihood Possible Evidence D

Monograph

Black Root: Uses, Safety & Side Effects

Medically reviewed by Dr. Brian Staiger, PharmD, BCPS · Reviewed July 2026 ·

The bottom line

Black Root is a traditional North American herb that was historically used as a strong laxative and to support digestion and liver function. There is very little modern scientific evidence to support these uses, and the fresh root can be toxic, so it should be used cautiously, if at all, and never during pregnancy or breastfeeding.

Scientific name: Veronicastrum virginicum
Family: Plantaginaceae
Part used: Dried root and rhizome
Common forms: Dried root, tincture, liquid extract, capsules, tea

People commonly use it for

Constipation
Liver and gallbladder complaints
Digestive upset
Stimulating bile flow

Popular and traditional uses — not proof it works. See “Uses & effectiveness” below for the evidence.

Safety at a glance

OverallUse caution

Modern safety data are limited and the fresh root can cause significant digestive toxicity.

PregnancyPossibly Unsafe

When the fresh root is used orally. Anecdotally, fresh black root has been reported for have abortifacient and teratogenic effects. However, there is...

Read the full pregnancy detail

BreastfeedingInsufficient reliable information

Insufficient reliable information available; avoid using.

Read the full breastfeeding detail

Pregnancy & breastfeeding ratings are from Natural Medicines (Therapeutic Research Center). Safety guidance is general; always confirm with your pharmacist or doctor for your situation.

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Overview

Black Root comes from Veronicastrum virginicum, a tall flowering plant native to North America. It is also sometimes called Culver's root. The part used in herbal preparations is the dried root and rhizome (the underground stem).

Native American communities and early American herbalists traditionally used Black Root as a powerful laxative and as a remedy for problems with the liver and gallbladder. It was often used to "cleanse" the digestive system and to encourage the flow of bile.

Today, Black Root is much less common and is mostly found in some traditional herbal blends, tinctures, and dried root preparations. It is not a mainstream supplement.

Uses & effectiveness

People have traditionally used Black Root for constipation, sluggish digestion, and complaints related to the liver and gallbladder. It was historically valued as a strong purgative (something that forces a bowel movement).

The scientific evidence behind these uses is very weak. There are no high-quality human studies that confirm Black Root works for any health condition. Most of what we know comes from historical and traditional use rather than modern research.

Because the evidence is so limited and the herb can be harsh on the body, Black Root is not recommended over safer, better-studied options for constipation or digestive concerns.

How it works

Black Root contains plant compounds, including bitter substances and saponin-like chemicals, that are thought to irritate the lining of the gut. This irritation may stimulate bowel movements and increase the flow of bile from the liver and gallbladder.

These proposed effects are mostly based on traditional use and basic chemistry rather than well-designed laboratory or human studies. The exact active compounds and how they work in the body are not well understood.

Importantly, the fresh (undried) root is considered more toxic than the properly dried and aged root, which is part of why traditional preparations called for drying the root before use.

Safety & precautions

Black Root should be used with caution. The fresh root is known to be toxic and can cause severe vomiting and diarrhea. Even the dried root acts as a strong laxative, which can lead to dehydration and loss of important minerals if overused.

People with inflammatory bowel disease, ongoing diarrhea, intestinal blockage, or unexplained abdominal pain should avoid it. Older adults and anyone who is already dehydrated should be especially careful.

Pregnancy: Avoid Black Root during pregnancy. Strong laxatives can be risky, and there is no reliable safety information.

Breastfeeding: Avoid Black Root while breastfeeding because there is not enough information to consider it safe.

Always talk to a pharmacist or doctor before using Black Root, especially if you take other medicines or have a health condition.

Side effects

The most common side effects relate to its laxative action, including stomach cramping, nausea, vomiting, and diarrhea. These can be severe, especially with the fresh root or with larger amounts.

Heavy or repeated use may cause dehydration and an imbalance of body salts such as potassium. In some cases, strong purgatives can cause significant weakness or dizziness.

If you experience severe vomiting, ongoing diarrhea, blood in the stool, or signs of dehydration, stop using it and seek medical care.

Black Root: Reported Adverse Effects

Documented safety reports on Black Root from the evidence-graded Natural Medicines (TRC Healthcare) database, shown word-for-word from the licensed record.

Orally, black root can cause abdominal pain or cramps, changes in stool color or odor, drowsiness, headache, nausea, and vomiting. Hepatotoxicity has been reported after ingestion of large amounts.

Fetrow CW, Avila JR. Professional's Handbook of Complementary & Alternative Medicines. 1st ed. Springhouse, PA: Springhouse Corp., 1999.

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.

Adverse-effects data: Natural Medicines, Therapeutic Research Center

Dosing

There is no established, standardized dose for Black Root, and modern dosing guidelines are lacking. Traditional preparations used the dried, aged root rather than the fresh root.

Because of the risk of toxicity and strong laxative effects, you should not guess at a dose. If you choose to use a product, follow the directions on the label exactly and start with the lowest amount.

Speak with a pharmacist or doctor before using Black Root to make sure it is appropriate for you and to discuss safer alternatives for constipation or digestive concerns.

Pregnancy & Breastfeeding

Black Root & Pregnancy

Possibly Unsafe

When the fresh root is used orally. Anecdotally, fresh black root has been reported for have abortifacient and teratogenic effects. However, there is no reliable scientific evidence about the effects of black root on pregnancy. Until more is known, black root should not be used during pregnancy.

Black Root & Breastfeeding

Insufficient reliable information

Insufficient reliable information available; avoid using.

Pregnancy & lactation ratings: Natural Medicines, Therapeutic Research Center

References & further reading

The 2 references that drive our Black Root 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.

Brinker F. Herb Contraindications and Drug Interactions. 2nd ed. Sandy, OR: Eclectic Medical Publications, 1998.
Fetrow CW, Avila JR. Professional's Handbook of Complementary & Alternative Medicines. 1st ed. Springhouse, PA: Springhouse Corp., 1999.

Keep reading

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.

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.

Brand directory

Brands that make products with Black Root

11 brands in our database make a supplement containing Black Root.

AB American Biologics 76 products Energique 31 products Hawaii Pharm 4,726 products Herb Pharm 3,320 products Herbal Terra 3,138 products Herbalist & Alchemist 613 products Herbs, Etc. 388 products Pascoe 7 products Pure Herbs 634 products Shaklee 268 products Viatrexx Bio Incorporated 16 products

Product directory

Supplement products with Black Root

42 products in our database contain Black Root. Open any to see its full ingredient list and every drug interaction we check.

Pharmacist Counseling Corner

Black Root: Common Questions

Does Black Root interact with prescription medications?

Yes. We list 78 medications with a known interaction with Black Root. Use the checker above to see how Black Root interacts with a specific drug.

How are Black Root interactions rated?

Each interaction is graded major, moderate, or minor based on how clinically significant it is and the strength of the evidence behind it. Major interactions are the most serious and are best avoided, or used only under close professional supervision.

Is it safe to take Black Root with my medications?

It depends on the specific medication. Some combinations are fine, while others call for monitoring, timing changes, or should be avoided. Check your exact drug above and confirm with your pharmacist or doctor before starting, stopping, or changing anything.

Where does this Black Root interaction information come from?

Our interaction data is built on the Natural Medicines database — an evidence-graded reference for vitamins, herbs, and supplements — and is reviewed by licensed HelloPharmacist pharmacists, who may add clinical context.

What is Black Root used for?

Black Root has traditionally been used as a strong laxative and as a remedy for liver, gallbladder, and digestive complaints. There is little modern scientific evidence that it works for any of these.

Is Black Root safe to take?

It should be used with caution. The fresh root can be toxic and cause severe vomiting and diarrhea, and even the dried root is a strong laxative that can cause dehydration. Check with a pharmacist or doctor first.

Can I take Black Root if I am pregnant or breastfeeding?

No. Black Root should be avoided during pregnancy and breastfeeding because of its strong laxative effect and the lack of reliable safety information.

What is the difference between fresh and dried Black Root?

The fresh root is considered more toxic and more likely to cause severe digestive upset, which is why traditional use called for drying and aging the root before it was taken.

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

Keep exploring

Products that contain Black Root

A rotating sample of real supplements in our database that list Black Root — open any to see its full ingredients and every drug interaction we check.

See all 42 products with Black Root →

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